阅读说明：本技术 一种信号处理方法及装置 (Signal processing method and device ) 是由 吕瑞 李昆 张鲁奇 于 2020-04-30 设计创作，主要内容包括：一种信号处理方法及装置,用以减少色散对传输信号的影响。该方法包括：发送端对第一信号进行同相正交IQ相位旋转处理,得到第二信号,并基于所述第二信号和第三信号确定需要发送给接收端的目标信号,其中,所述第一信号为待调制信号和直流信号中的其中一个信号；所述第三信号为所述待调制信号和所述直流信号中除所述第一信号之外的信号。这样可以通过改变系统中基带直流分量与待调制信号的相对旋转相位,改变ISI干扰在扩展接收信号的星座点时,对接收信号功率的影响,从而可以提升系统抗色散的能力,从而减少色散对传输信号的影响。(A signal processing method and apparatus for reducing the effect of chromatic dispersion on a transmission signal. The method comprises the following steps: the method comprises the steps that a sending terminal carries out in-phase quadrature IQ phase rotation processing on a first signal to obtain a second signal, and a target signal needing to be sent to a receiving terminal is determined based on the second signal and a third signal, wherein the first signal is one of a signal to be modulated and a direct current signal; the third signal is a signal except the first signal in the signal to be modulated and the direct current signal. Therefore, the influence of ISI interference on the power of the received signal when the constellation point of the received signal is expanded can be changed by changing the relative rotation phase of the baseband direct current component and the signal to be modulated in the system, so that the anti-dispersion capability of the system can be improved, and the influence of dispersion on the transmitted signal can be reduced.)

1. A signal processing method, comprising:

a sending end carries out in-phase quadrature IQ phase rotation processing on a first signal to obtain a second signal, wherein the first signal is one of a signal to be modulated and a direct current signal;

the transmitting end determines a target signal to be transmitted to a receiving end based on the second signal and the third signal; and the third signal is a signal except the first signal in the signal to be modulated and the direct current signal.

2. The method of claim 1, wherein when the first signal is the dc signal and the third signal is the signal to be modulated, the determining, by the transmitting end, a target signal based on the second signal and the third signal comprises:

the sending end combines the second signal and the signal to be modulated into a fourth signal;

and the transmitting end carries out carrier modulation on the fourth signal based on the carrier signal to obtain the target signal.

3. The method according to claim 1, wherein when the first signal is the dc signal and the third signal is the signal to be modulated, the dc signal is obtained by modulating a carrier signal; the transmitting end determines a target signal based on the second signal and the third signal, including:

the sending end carries out carrier modulation on the signal to be modulated based on the carrier signal to obtain a fifth signal;

and the transmitting end combines the fifth signal and the second signal into the target signal.

4. The method of claim 1, wherein when the first signal is the signal to be modulated and the third signal is the direct current signal, the determining, by the transmitting end, a target signal based on the second signal and the third signal comprises:

the sending end combines the second signal and the direct current signal into a sixth signal;

and the sending end carries out carrier modulation on the sixth signal based on the carrier signal to obtain the target signal.

5. The method of any one of claims 1-3, wherein the target signal conforms to the following equation:

wherein, C [ n ]]Is the target signal; s [ n ]]For the signal to be modulated, the signal to be modulated is a real signal with the average value of 0; DC is the direct current signal;is a phase offset; f. of_cIs the carrier frequency.

6. A signal processing apparatus, characterized by comprising:

the device comprises a first processing unit, a second processing unit and a control unit, wherein the first processing unit is used for carrying out in-phase quadrature (IQ) phase rotation processing on a first signal to obtain a second signal, and the first signal is one of a signal to be modulated and a direct current signal;

the second processing unit is used for determining a target signal which needs to be sent to a receiving end based on the second signal and the third signal; and the third signal is a signal except the first signal in the signal to be modulated and the direct current signal.

7. The apparatus according to claim 6, wherein when the first signal is the dc signal and the third signal is the signal to be modulated, the second processing unit, when determining the target signal based on the second signal and the third signal, is specifically configured to:

combining the second signal and the signal to be modulated into a fourth signal;

and carrying out carrier modulation on the fourth signal based on the carrier signal to obtain the target signal.

8. The apparatus according to claim 6, wherein when the first signal is the dc signal and the third signal is the signal to be modulated, the dc signal is obtained by modulating a carrier signal; when determining the target signal based on the second signal and the third signal, the second processing unit is specifically configured to:

carrying out carrier modulation on the signal to be modulated based on the carrier signal to obtain a fifth signal;

combining the fifth signal and the second signal into the target signal.

9. The apparatus according to claim 6, wherein when the first signal is the signal to be modulated and the third signal is the dc signal, the second processing unit, when determining the target signal based on the second signal and the third signal, is specifically configured to:

combining the second signal and the direct current signal into a sixth signal;

and carrying out carrier modulation on the sixth signal based on the carrier signal to obtain the target signal.

10. The apparatus of any one of claims 6-8, wherein the target signal conforms to the following equation:

wherein, C [ n ]]Is the target signal; s [ n ]]For the signal to be modulated, the signal to be modulated is a real signal with the average value of 0; DC is the direct current signal;is a phase offset; f. of_cIs the carrier frequency.

11. A computer-readable storage medium, in which a computer program is stored which, when executed by a computer, causes the computer to carry out the method according to any one of claims 1 to 5.

Technical Field

The present application relates to the field of communications technologies, and in particular, to a signal processing method and apparatus.

Background

With the continuous expansion of data center scale and the high-speed increase of data traffic, the demand of interconnection scale and transmission rate between various cabinet devices is increasing, and a short-distance interconnection system with low cost, low power consumption and high rate becomes a basic application demand of the market.

Under the market trend that the demand for transmission rate is continuously rising, more and more attention and applications are paid to optical fibers and Terahertz Active Cables (TAC) with larger transmission bandwidth and lower material cost. Due to the influence of material characteristics and signal transmission modes, the optical fiber and the TAC can introduce dispersion damage into transmitted light and electromagnetic waves, so that distortion of a transmission signal occurs. Since the dispersion coefficient and transmission loss of TAC are orders of magnitude larger than those of optical fibers, the influence of dispersion damage thereof becomes more serious.

In order to reduce the cost and power consumption, the transceiver module of the short-range interconnection system generally uses a simple modulation and demodulation method, for example, the transmitting end generally uses a non-return-to-zero (NRZ) or 4 pulse amplitude modulation (PAM 4) amplitude modulation method to modulate signals, and the receiving end demodulates signals by using a Direct Detection (DD) method. Since the signal processing capability of the short-distance interconnection system is very limited, the system performance is seriously deteriorated when the system is faced with channel damage such as dispersion caused by a transmission line. For example, dispersion causes pulse spreading, which causes inter-symbol interference (ISI) in the received symbol sequence, and adjacent symbol crosstalk further degrades the signal-to-interference plus noise ratio (SINR) of normal symbols in addition to noise, resulting in symbol decision errors. When ISI increases to a certain extent, it causes the eye pattern of the received signal to close, resulting in communication interruption.

At present, an anti-dispersion method such as equalization is usually used to avoid the above problems, however, the use of an anti-dispersion method such as equalization is very costly, and a simple anti-dispersion method is not available in the current amplitude modulation-direct detection system.

Disclosure of Invention

The present application provides a signal processing method and apparatus, which is used to provide a signal processing method to reduce the influence of chromatic dispersion on transmission signals.

In a first aspect, the present application provides a signal processing method, including: the method comprises the steps that a sending end carries out in-phase quadrature IQ phase rotation processing on a first signal to obtain a second signal, and a target signal needing to be sent to a receiving end is determined based on the second signal and a third signal; the first signal is one of a signal to be modulated and a direct current signal; the third signal is a signal except the first signal in the signal to be modulated and the direct current signal.

By the method, the influence of ISI interference on the power of the received signal when the constellation point of the received signal is expanded can be changed by changing the relative rotation phase of the baseband direct current component and the signal to be modulated in the system, so that the anti-dispersion capability of the system can be improved, and the influence of dispersion on the transmitted signal can be reduced. Moreover, the anti-dispersion capability of the system is improved without depending on the equalization processing of the receiving end, and the realization complexity and difficulty of the receiving end are greatly simplified. Meanwhile, the system can bear larger channel dispersion damage than the traditional amplitude modulation-direct detection system, so that longer transmission distance is supported in the existing dispersion limited system.

In a possible design, when the first signal is the dc signal and the third signal is the signal to be modulated, the sending end determines a target signal based on the second signal and the third signal, and the specific method may be as follows: and the sending end combines the second signal and the signal to be modulated into a fourth signal, and carries out carrier modulation on the fourth signal based on a carrier signal to obtain the target signal. Therefore, the influence of ISI interference on the power of the received signal when the constellation point of the received signal is expanded can be changed by changing the relative rotation phase of the baseband direct current component and the signal to be modulated in the system, so that the anti-dispersion capability of the system can be improved, and the influence of dispersion on the transmitted signal can be reduced.

In a possible design, when the first signal is the dc signal and the third signal is the signal to be modulated, the dc signal is obtained by modulating a carrier signal; the sending end determines a target signal based on the second signal and the third signal, and the specific method may be as follows: and the sending end carries out carrier modulation on the signal to be modulated based on the carrier signal to obtain a fifth signal, and the fifth signal and the second signal are combined into the target signal. Therefore, the influence of ISI interference on the power of the received signal when the constellation point of the received signal is expanded can be changed by changing the relative rotation phase of the baseband direct current component and the signal to be modulated in the system, so that the anti-dispersion capability of the system can be improved, and the influence of dispersion on the transmitted signal can be reduced.

In a possible design, when the first signal is the signal to be modulated and the third signal is the dc signal, the sending end determines a target signal based on the second signal and the third signal, and the specific method may be as follows: and the sending end combines the second signal and the direct current signal into a sixth signal, and carries out carrier modulation on the sixth signal based on a carrier signal to obtain the target signal. Therefore, the capability of resisting dispersion of the system can be improved, and the influence of dispersion on a transmission signal is reduced.

In one possible design, the target signal may conform to the following equation:

wherein, C [ n ]]Is the target signal; s [ n ]]For the signal to be modulated, the signal to be modulated is a real signal with the average value of 0; DC is the direct current signal;is a phase offset; f. of_cIs the carrier frequency.

The method can change the influence of ISI interference on the power of the received signal when the constellation point of the received signal is expanded by changing the relative rotation phase of the baseband direct current component and the signal to be modulated in the system, thereby improving the anti-dispersion capability of the system and reducing the influence of dispersion on the transmitted signal.

In a second aspect, the present application further provides a signal processing apparatus, where the signal processing apparatus may be a transmitting end, and the signal processing apparatus has a function of implementing the transmitting end in the first aspect or each possible design example of the first aspect. The functions can be realized by hardware, and the functions can also be realized by executing corresponding software by hardware. The hardware or software includes one or more modules or units corresponding to the above functions.

In one possible design, the structure of the signal processing apparatus may include a plurality of processing units, such as a first processing unit and a second processing unit, which may perform corresponding functions in the first aspect or each possible design example of the first aspect, for which specific reference is made to detailed descriptions in the method examples, and details are not repeated here.

In one possible design, the signal processing apparatus includes a processor and a transceiver in its structure, and optionally may further include a memory. The transceiver is used for transceiving signals and for communicative interaction with other devices in the communication system. The processor is configured to enable the signal processing apparatus to perform the corresponding functions in the first aspect or each of the possible design examples of the first aspect. The memory is coupled to the processor and retains program instructions and data necessary for the signal processing device.

In a third aspect, an embodiment of the present application provides a communication system, which may include the above-mentioned transmitting end and receiving end.

In a fourth aspect, an embodiment of the present application provides a computer-readable storage medium, which stores program instructions, and when the program instructions are executed on a computer, the computer is caused to execute the first aspect and any possible design thereof. By way of example, computer readable storage media may be any available media that can be accessed by a computer. Taking this as an example but not limiting: a computer-readable medium may include a non-transitory computer-readable medium, a random-access memory (RAM), a read-only memory (ROM), an electrically erasable programmable read-only memory (EEPROM), a CD-ROM or other optical disk storage, a magnetic disk storage medium or other magnetic storage device, or any other medium that can be used to carry or store desired program code in the form of instructions or data structures and that can be accessed by a computer.

In a fifth aspect, the present application provides a computer program product comprising computer program code or instructions which, when run on a computer, enable the computer to implement the method of any one of the possible designs of the first aspect.

In a sixth aspect, the present application further provides a chip, coupled to a memory, for reading and executing program instructions stored in the memory to implement the method in any one of the possible designs of the first aspect.

For each of the second to sixth aspects and possible technical effects of each aspect, please refer to the above description of the possible technical effects of each possible solution in the first aspect, and no repeated description is given here.

Drawings

Fig. 1 is an architecture diagram of a communication system provided herein;

fig. 2 is a flowchart of a signal processing method provided in the present application;

FIG. 3 is a schematic diagram of a signal processing process provided herein;

FIG. 4 is a schematic diagram of another signal processing process provided herein;

FIG. 5 is a schematic diagram of another signal processing process provided herein;

fig. 6 is a block diagram of a transceiver system provided in the present application;

fig. 7 is a schematic diagram of a signal constellation provided in the present application;

fig. 8 is a schematic diagram of a signal constellation provided in the present application;

fig. 9 is a schematic diagram of a signal constellation provided in the present application;

fig. 10 is a schematic diagram of a signal constellation provided in the present application;

fig. 11 is a circuit diagram of an amplitude modulation circuit provided in the present application;

fig. 12 is a schematic diagram of a signal constellation provided in the present application;

fig. 13 is a schematic diagram of a signal constellation provided in the present application;

fig. 14 is a schematic diagram of a signal constellation provided in the present application;

fig. 15 is a circuit diagram of an amplitude modulation circuit provided in the present application;

fig. 16 is a circuit diagram of a direct modulation scheme provided in the present application;

fig. 17 is a schematic diagram of a signal constellation provided in the present application;

fig. 18 is a schematic diagram of a signal constellation provided in the present application;

fig. 19 is a schematic structural diagram of a signal processing apparatus provided in the present application;

fig. 20 is a block diagram of a signal processing apparatus according to the present application.

Detailed Description

The present application will be described in further detail below with reference to the accompanying drawings.

The embodiment of the application provides a signal processing method and a signal processing device, which are used for providing a signal processing method to reduce the influence of chromatic dispersion on a transmission signal. The method and the device are based on the same technical concept, and because the principles of solving the problems of the method and the device are similar, the implementation of the device and the method can be mutually referred, and repeated parts are not repeated.

At present, in a scene using an optical fiber, TAC, or the like as a transmission material, a transmitting end usually uses an amplitude modulation method such as NRZ or PAM4 to change the amplitude of a transmission carrier wave by using different information; after channel transmission, the receiving end extracts the amplitude variation from the received carrier wave by using a power detection or envelope detection mode, thereby recovering the transmitted signal. However, when the channel damage such as dispersion caused by the transmission line is faced, the system performance will be seriously deteriorated. For the purpose of dispersion resistance, the currently adopted schemes may have two kinds:

in one scheme, since the transmitting end and the receiving end have no complex signal processing function, the anti-dispersion method is generally implemented in a non-signal processing manner. For example, by inserting a section of anomalous dispersion fiber intermittently in the transmission channel, the average dispersion coefficient of the entire transmission channel is reduced; or, by controlling parameters such as modulation modes, signal transmission speeds, signal waveforms and the like used by the sending end and the receiving end under different transmission distances, the distortion of the received signals caused by dispersion damage is controlled within a certain degree, and thus normal transceiving communication is realized.

In this solution, the essence of this technical means is to avoid the dispersion from causing fatal distortion to the signal quality by changing the characteristics of the transmission line itself or limiting the system's ability to utilize the transmission line. But physically changing the transmission line characteristics can involve alterations and permutations in transmission line design, structure, or materials, resulting in increased cost and increased deployment difficulty. As application requirements continue to increase, this approach to avoid ISI by limiting system rate is ineffective when the transmission distance and bandwidth requirements approach or exceed the dispersion control threshold of the transmission line. This drawback is particularly evident in TAC systems.

In another scheme, an equalizer is added at the transmitting end or the receiving end to compensate for signal distortion caused by chromatic dispersion ISI, thereby improving the capability of the communication system to combat channel damage. In a high baud rate system, the implementation difficulty of the equalizer increases dramatically, and a large cost and power consumption cost are incurred.

In conclusion, neither of the above two schemes is very dispersion resistant and is not widely used. Based on this, the application provides a signal processing method, which designs an amplitude modulation mode relatively insensitive to dispersion ISI, and greatly improves the bearing capacity of directly detecting the total dispersion of a transmission system by a receiving end under the condition of not depending on ISI compensation technologies such as equalization and the like. Therefore, the signal processing method provided by the application can be well resistant to dispersion so as to reduce the influence of dispersion on the transmission signal.

In the description of the present application, the terms "first," "second," and the like, are used for descriptive purposes only and are not to be construed as indicating or implying relative importance, nor order.

In order to more clearly describe the technical solutions of the embodiments of the present application, the following describes in detail a signal method and a signal device provided by the embodiments of the present application with reference to the accompanying drawings.

Fig. 1 shows a possible architecture of a communication system to which the signal processing method provided in the embodiment of the present application is applicable, where the architecture of the communication system includes a sending end and a receiving end, where a transmission line between the sending end and the receiving end is an optical fiber and a TAC with a large transmission bandwidth and a low material cost.

For example, the transmitting end may be, but is not limited to, a transmitting chip of a quad small-connector (QSPF), or a device or apparatus including the transmitting chip, or a transmitter of a terahertz (THz) communication system; the receiving end may be, but is not limited to, a receiving chip of QSPF, or a device or apparatus including the receiving chip, or a receiver of THz communication system.

The signal processing method provided by the embodiment of the application is suitable for the communication system shown in fig. 1. Referring to fig. 2, the specific process of the method includes:

step 201, a sending end performs in-phase/quadrature (IQ) phase rotation processing on a first signal to obtain a second signal, wherein the first signal is one of a signal to be modulated and a direct current signal.

The signal to be modulated is a real baseband signal which needs to be sent by the sending end.

Step 202, the transmitting end determines a target signal to be transmitted to a receiving end based on the second signal and the third signal; and the third signal is a signal except the first signal in the signal to be modulated and the direct current signal. The target signal may also be referred to as a modulated signal.

In an optional implementation manner, according to different situations of the first signal and the third signal, the signal processing procedure at the transmitting end may include at least the following three examples:

in a first example, when the first signal is the dc signal and the third signal is the signal to be modulated, the sending end determines the target signal based on the second signal and the third signal, and the specific method may be as follows: the sending end combines the second signal and the signal to be modulated into a fourth signal, and performs carrier modulation on the fourth signal based on a carrier signal to obtain the target signal (i.e., the modulated signal). For example, the signal processing procedure of the modulated signal obtained by the transmitting end may be as shown in fig. 3.

Specifically, the dc signal may be converted into a complex baseband signal after IQ phase rotation.

In a second example, when the first signal is the dc signal and the third signal is the signal to be modulated, the dc signal is obtained after modulation of a carrier signal; the sending end determines a target signal based on the second signal and the third signal, and the specific method may be as follows: the sending end carries out carrier modulation on the signal to be modulated based on the carrier signal to obtain a fifth signal, and combines the fifth signal and the second signal into the target signal (namely the modulated signal). For example, the signal processing procedure of the modulated signal obtained by the transmitting end may be as shown in fig. 4.

It should be noted that, in this example, since the carrier signal itself can also be regarded as a modulated dc signal, the signal processing procedure shown in fig. 4 in this example can be obtained by exchanging the order of the carrier modulation operation and the signal combining operation in fig. 3 in the first example.

Specifically, in this example, the signal to be modulated is subjected to carrier modulation to obtain a modulation signal (i.e., the fifth signal) in a carrier frequency band; the carrier signal is subjected to IQ phase rotation to obtain a bandpass real signal (i.e., the second signal).

In a third example, when the first signal is the signal to be modulated and the third signal is the dc signal, the sending end determines a target signal based on the second signal and the third signal, and a specific method may be as follows: the sending end combines the second signal and the direct current signal into a sixth signal; and carrier-modulating the sixth signal based on a carrier signal to obtain the target signal (i.e., the modulated signal). For example, the signal processing procedure of the modulated signal obtained by the transmitting end may be as shown in fig. 5.

In a specific implementation manner, taking the method in the first example as an example, a block diagram of a transceiving system formed by the transmitting end and the receiving end may be as shown in fig. 6. Wherein, the transmitting end uses the modulation method in the first example to treat the transmitted signal (i.e. the signal to be modulated) S [ n ]]Modulating (i.e. the signal processing method in the first example) to obtain a target signal C [ n ] that the transmitting end needs to send to the receiving end](may also be referred to as a transmit signal); the receiving end pair receives a signal J [ n [ ]]The amplified signal is sent to a self-mixer for detection, the self-mixer can be replaced by other types of Power Detectors (PD) or Envelope Detectors (ED), and the output obtained after the detection result is subjected to low-pass filtering is the power | J [ n ] of the received signal]|²And finally, the receiving end judges the signal power through a decision device to recover the corresponding transmission signal.

Specifically, the principle of dispersion resistance applied in the present application may be as follows:

the dispersion of the channel appears as a second-order component of the channel phase-frequency response in the signal transmission model, and the corresponding signal transmission model may conform to the following equation (1):

R(f)＝S(f)·H(f)＝S(f)·exp(2πj·βLf²) Formula (1);

wherein, s (f) and r (f) are frequency spectrums of the transmission signal and the reception signal, respectively, and h (f) is a frequency response of the entire transmission channel. The frequency response of the entire transmission channel includes a channel amplitude-frequency response and a channel phase-frequency response, and the channel phase-frequency response may include a first-order component and a second-order component. Here, since the influence of the channel amplitude-frequency response is not considered, the channel amplitude-frequency fluctuation is not reflected in the formula (1), or the channel amplitude-frequency response in the formula (1) is 1. Since the first-order component of the phase-frequency response of the channel only affects the overall transmission delay of the signal in the channel and does not distort the signal waveform, it is omitted from equation (1), i.e., in equation (1), for simplicityIn the formula (1), only the second-order component exp (2 pi j · β Lf) of the channel phase-frequency response is expressed²). In the second-order component of the channel phase-frequency response, beta is the dispersion coefficient of the transmission line, and L is the transmission distance, and the two jointly determine the total degree of dispersion.

Further, according to the property of fourier transform, the second-order component of the channel phase-frequency response in formula (1) will be represented as a second-order phase change in the channel impulse response in the time domain, which may specifically conform to the following formula (2):

where h (t) is the channel impulse response, A is a complex constant, and α is a coefficient determined by the total dispersion in the transmission channel. T in parentheses on the right side according to formula (2)²The component may derive a first characteristic of a second order dispersive time-domain channel: the impulse response h (t) of the channel is symmetrical about the channel response with the center position t being 0, namely the amplitude and the phase of the channel impulse response h (-t0) at the position t being-t 0 are equal to the amplitude and the phase of the channel impulse response h (t0) at the position t being t 0.

Under the condition of limited bandwidth, according to the principle of stationary phase, the channel impulse response of formula (2) exhibits the second characteristic: the channel impulse response amplitude is larger only near the center position, and the channel impulse response amplitude of the two sides outwards decreases sharply with the distance from the center position.

In the time domain impulse response of a transmission channel, an impulse response coefficient h (0) with a center position t being 0 is the transmission loss and phase transformation of a main signal (i.e. a signal except an interference signal); and the impulse response coefficient of the non-central position t ≠ 0 corresponds to the ISI interference of the channel. From the above two characteristics of the channel impulse response, it can be seen that during the process of gradually increasing the second-order dispersion effect, a pair of symmetric ISI interferences appears on both sides of the main signal position at the same time, and due to the characteristic that ISI rapidly decays with distance, before the amplitudes of two ISI adjacent to both sides of the main signal response increase to approach the amplitude of the main signal response, the ISI interferences further outside the two ISI interferences increase by a small amplitude.

If the symbol sequence (i.e., the target signal) sent by the sending end is cn, where n is an integer, and after the channel transmission, the symbol sequence (i.e., the received signal) received by the receiving end is pn, then pn and cn may conform to the following formula (3):

where h [ i ] represents the discretized channel impulse response, k represents the sequence number of the channel ISI spread on both sides of the central response, and N is the channel noise. Due to the symmetry of ISI and the fast fading characteristics, before ISI spreads over a large range, equation (3) can be simplified as follows (4):

where complex number A represents the impulse response coefficient of the main signal and complex number I₁The interference coefficients representing the two strongest ISI responses, the other ISI interference being weaker, are collectively referred to as the noise term O. The inequality in equation (4) characterizes the upper bound of ISI interference, where coherent superposition occurs on the transmitted signal at times n +1 and n-1, and ISI interference is largest. Finally, the relative ISI interference coefficients of adjacent transmitted signals can be expressed in terms of magnitude γ and phase θ by an equality transformation.

According to the method, the dispersion resistance of the receiving end direct detection receiver is improved by introducing the DC component with the phase offset (namely introducing IQ phase rotation) during signal processing. Based on the above principle, the target signal obtained by the signal processing method (i.e. amplitude modulation mode) provided by the present application may conform to the following formula (5):

wherein, C [ n ]]For the target signal (i.e. hair)Send a signal); s [ n ]]For the signal to be modulated, the signal to be modulated is a real signal with the average value of 0; DC is the direct current signal;is a phase offset; f. of_cIs the carrier frequency.

In the above equation (5), the parameters of the phase offsetDoes not change the amplitude of the DC component, so that the transmission signal Cn]Is not varied with phase offset. Due to S [ n ]]Is a real signal with an average value of 0, and thus C [ n ]]Can be written in the right-most complex form of equation (5). At this time, the transmission signal C [ n ] in FIG. 6]May be as shown in fig. 7.

Further, after the channel transmission, the receiving signal J [ n ] at the receiving end may conform to the following formula (6):

wherein the first term in equation (6) is the fixed dc offset component and the second term is the useful signal term after being interfered by adjacent ISI.

The receiving end obtains the power | J [ n ] of the received signal after detection]|²The decision principle of the decision device for the signal power is equivalent to receiving the signal J [ n ] on the constellation diagram]The radius of the circle determines the original signal S [ n ] to be modulated]As shown in fig. 8, in the constellation diagram of the signal received by the receiving end after signal processing by the method of the present application, four black rings respectively correspond to the signal S [ n ] sending four different values]And the variation range of the output signal power of the receiver detector.

It can be deduced from a simple geometric principle that when the extending direction of ISI interference to a constellation point is tangent to a power detection circle, the ISI extension has the smallest broadening to the power detection circle and the smallest deterioration to the receiver detection performance. After the phase offset is performed according to this principle, the constellation diagram of the received signal corresponding to the formula (6) is changed to the one shown in fig. 8.

At this time, J [ n ]]DC component after medium rotationThe vector of (a) points exactly orthogonal to the direction of spreading of the constellation point by the ISI interference.

In the following, the performance of a standard PAM4 modulation system used in the prior art under the same dispersive channel is compared with the signal processing method provided in the present application. At this time, a baseband signal constellation of a transmission signal of a standard PAM4 modulation system used in the related art is shown in fig. 9.

After the channel transmission, the constellation diagram of the received signal determined by the receiving end and the power variation range of the detector output are as shown in fig. 10.

At this time, the innermost gray ring in fig. 10 is very close to the immediately adjacent gray ring, and when the decision device decides the transmission signals corresponding to the two rings in a noise environment, the probability of error is greatly increased. As can be seen from comparison between fig. 10 and fig. 8, the distances between all the circular rings in fig. 8 are very large, and the signal processing method (amplitude modulation method) of the present application still maintains high receiving performance at the receiving end under the interference of channel dispersion ISI, and greatly improves the anti-dispersion performance.

Specifically, it can be seen from a comparison between fig. 10 and fig. 8 that, by using the signal processing method provided by the present application, the influence of ISI interference on the received signal power when the constellation point of the received signal is expanded can be changed by changing the relative rotation phase between the baseband dc component in the amplitude modulation system and the signal to be modulated, so that the anti-dispersion performance of the direct detection receiving system is greatly improved. The improvement of the system performance does not depend on the equalization processing of the receiving end, and the realization complexity and difficulty of the receiving end are greatly simplified. Meanwhile, the system can bear larger channel dispersion damage than the traditional amplitude modulation-direct detection system, so that longer transmission distance is supported in the existing dispersion limited system.

In a specific example, the signal processing of the above equation (5) is employedThe method may be implemented by an amplitude modulation circuit diagram as shown in fig. 11. In particular, f_cIs the carrier frequency of the transmitted signal, cos (f)_ct) and sin (f)_ct) are two orthogonal carrier oscillators. Decomposing the DC component after IQ phase rotation into real component according to the technical principle of equation (5)And imaginary componentAnd superimposes the real component of DC on the signal S [ n ] to be modulated in advance]The intermediate frequency signal is used as an I path signal, the DC imaginary component is used as a Q path signal, and then the carrier modulation and the combination are realized through an IQ modulator.

It should be noted that the I, Q two paths of signals input by the IQ modulator may be directly constructed using an analog baseband waveform, or may be calculated in a digital chip to generate corresponding numerical signals, and then converted into analog signals by a digital-to-analog converter (D/a), which is not limited in this application.

In the example shown in fig. 11, assuming that S [ n ] to be transmitted at this time is a 2-bit signal, the signal constellation corresponding to the a point may be as shown in fig. 12; the signal constellation corresponding to the B point may be as shown in fig. 13; point C may obtain a constellation diagram formed by the I, Q two-way signals on the I/Q plane when finally performing IQ modulation, as shown in fig. 14, where the distribution of the constellation diagram shown in fig. 14 is consistent with the distribution of the constellation diagram shown in fig. 7.

In this example, the circuit structure and operation of the receiving end are substantially the same as those of the receiving end in fig. 6. As is readily demonstrated by the nature of the vector sum, the DC component, after IQ phase rotation, is phase-rotated for each signal Cn]The power circle radius of the constellation point is changed, so as shown in fig. 11, when the decision device at the receiving end performs demodulation decision on the signal, its decision threshold also needs to be determined according to the phase of the DC rotation at the transmitting endAnd (6) adjusting.

In determining to sendDC rotating phase with end configurationWhen taking the optimal value of (a), one way may be to obtain the phase difference θ between the interference coefficient of the strongest ISI and the response coefficient of the main signal at the receiving end through channel estimation, and then calculate the required phase according to the aforementioned principle of making the DC component after rotation orthogonal to the spreading direction of the ISIAnother way may be that, by detecting an output signal eye diagram in a receiving end or detecting an error rate after demodulation, optimal search is performed on a required rotation phase, so that opening and closing of multiple eyes in the signal eye diagram are balanced at this time, or the error rate is the lowest, and at this time, as shown in fig. 11, an eye diagram monitoring or error code monitoring functional module needs to be added in the receiving end.

In another specific example, a circuit diagram (which may be referred to as an amplitude modulation circuit diagram) including DC component IQ phase rotation in the signal processing of the transmitting end may be as shown in fig. 15. In this example, the real component DC · cos after the DC component rotationIn a display mode with the signal S [ n ] to be modulated]Combining, and then obtaining a signal after carrier modulation through a single carrier modulator; the addition of the imaginary component after the DC rotation is realized by a branch coupling circuit at the rear side of the single carrier modulator. The branch coupling circuit directly takes a modulated carrier as input, and the input carrier signal is equivalent to a direct current signal subjected to carrier modulation; the branch coupling circuit includes a phase shifter operating in the carrier band and a gain controller (which may be an amplifier or an attenuator, etc.). Wherein, the phase shifter makes the carrier signal corresponding to the DC imaginary component have a 90-degree difference with the carrier signal in the modulation signal at the rear signal merging point by phase shift, and the gain controller makes the carrier amplitude of the branch satisfy the formula (5) by adjusting the gainThe relationship (2) of (c).

In yet another specific example, a circuit diagram (which may be referred to as a circuit diagram of a direct modulation scheme) including DC IQ phase rotation in the signal processing of the transmitting end may be as shown in fig. 16. A conventional direct modulator can directly control the amplitude of a single-tone carrier signal with a gain of K according to the value of a signal to be modulated, for example, for microwave signal modulation, the direct modulator can be an electric control switch working in a microwave frequency band; for optical signal modulation, the direct modulator may be an externally tuned laser. The direct modulator directly realizes the functions of DC real component superposition and carrier modulation. While the introduction of the DC imaginary component is still achieved with a branch coupling circuit structure, the internal structure and function of the branch coupling circuit is similar to the branch coupling circuit referred to in fig. 15. Assuming that the modulation gain of the linear modulator is 1 and the modulation depth of the linear modulator under the minimum value is H, i.e. the intensity of the output signal of the linear modulator is H when the signal to be modulated takes the minimum value, in order to realize the phase position as HThe amplification gain in the branch coupling circuit needs to be configured to

In the above examples, both the first example and the second example described above have been described in detail, in which the IQ rotation is performed on the dc signal during the signal processing. When IQ phase rotation is performed on the direct current component, the reference object of the rotation is a baseband signal S [ n ] to be modulated]Itself. Therefore, it can be further understood that the IQ phase of the relative position of the dc component in the baseband signal (i.e., the signal to be modulated) and the baseband signal is rotated, thereby obtaining the situation in the third example, i.e., the signal processing procedure shown in fig. 5. In a third example, the dc signal is not further IQ phase rotated, but is IQ phase rotated with the signal to be modulated and then is compared with the dc signalAfter the component combination of the flows, the carrier modulation is carried out. Angle of IQ phase rotationThe IQ phase rotation is performed on the dc component by the same angle as in the above example, but with the opposite sign. Taking a 2-bit signal to be modulated as an example, in the modulation process, a signal constellation diagram corresponding to the point a in fig. 5 may be as shown in fig. 17; further, after combining with the dc signal, the constellation diagram corresponding to the B point may be as shown in fig. 18.

Comparing the constellation diagram shown in fig. 18 with the constellation diagram shown in fig. 14, it can be seen that the constellation diagram in fig. 18 only has an overall rotation with respect to the origin, and the rotation does not affect the normal demodulation and anti-dispersion performance of the system. Therefore, the third example and the first example are consistent with the second example in the effect of dispersion resistance.

By adopting the signal processing method in the embodiment of the application, the influence of ISI interference on the power of a received signal when the constellation point of the received signal is expanded can be changed by changing the relative rotation phase of the baseband direct current component and the signal to be modulated in the system, so that the anti-dispersion capability of the system can be improved, and the influence of dispersion on the transmitted signal can be reduced. Moreover, the anti-dispersion capability of the system is improved without depending on the equalization processing of the receiving end, and the realization complexity and difficulty of the receiving end are greatly simplified. Meanwhile, the system can bear larger channel dispersion damage than the traditional amplitude modulation-direct detection system, so that longer transmission distance is supported in the existing dispersion limited system.

Based on the foregoing embodiments, an embodiment of the present application further provides a signal processing apparatus, which is used for implementing the signal processing method provided in the embodiment shown in fig. 2. The signal processing apparatus may be a transmitting end in the foregoing embodiment, and specifically may be a processor, a chip or a chip system, or a functional module in the transmitting end. Referring to fig. 19, the signal processing apparatus 1900 includes a first processing unit 1901 and a second processing unit 1902, wherein:

the first processing unit 1901 is configured to perform in-phase quadrature IQ phase rotation processing on a first signal to obtain a second signal, where the first signal is one of a signal to be modulated and a direct current signal; the second processing unit 1902 is configured to determine, based on the second signal and the third signal, a target signal that needs to be sent to a receiving end; and the third signal is a signal except the first signal in the signal to be modulated and the direct current signal.

In an optional implementation manner, when the first signal is the direct current signal and the third signal is the signal to be modulated, the second processing unit 1902, when determining a target signal based on the second signal and the third signal, is specifically configured to: and combining the second signal and the signal to be modulated into a fourth signal, and carrying out carrier modulation on the fourth signal based on a carrier signal to obtain the target signal.

In another optional implementation manner, when the first signal is the direct current signal and the third signal is the signal to be modulated, the direct current signal is obtained after modulation of a carrier signal; the second processing unit 1902, when determining the target signal based on the second signal and the third signal, is specifically configured to: and carrying out carrier modulation on the signal to be modulated based on the carrier signal to obtain a fifth signal, and combining the fifth signal and the second signal into the target signal.

In another optional implementation manner, when the first signal is the signal to be modulated and the third signal is the dc signal, the second processing unit 1902, when determining the target signal based on the second signal and the third signal, is specifically configured to: and combining the second signal and the direct current signal into a sixth signal, and carrying out carrier modulation on the sixth signal based on a carrier signal to obtain the target signal.

Illustratively, the target signal may conform to the following equation:

wherein, C [ n ]]Is the targetA signal; s [ n ]]For the signal to be modulated, the signal to be modulated is a real signal with the average value of 0; DC is the direct current signal;is a phase offset; f. of_cIs the carrier frequency.

By adopting the signal processing device in the embodiment of the application, the influence of ISI interference on the power of a received signal when the constellation point of the received signal is expanded can be changed by changing the relative rotation phase of the baseband direct current component and the signal to be modulated in the system, so that the anti-dispersion capability of the system can be improved, and the influence of dispersion on the transmitted signal can be reduced. Moreover, the anti-dispersion capability of the system is improved without depending on the equalization processing of the receiving end, and the realization complexity and difficulty of the receiving end are greatly simplified. Meanwhile, the system can bear larger channel dispersion damage than the traditional amplitude modulation-direct detection system, so that longer transmission distance is supported in the existing dispersion limited system.

It should be noted that the division of the unit in the embodiment of the present application is schematic, and is only a logic function division, and there may be another division manner in actual implementation. The functional units in the embodiments of the present application may be integrated into one processing unit, or each unit may exist alone physically, or two or more units are integrated into one unit. The integrated unit can be realized in a form of hardware, and can also be realized in a form of a software functional unit.

The integrated unit, if implemented in the form of a software functional unit and sold or used as a stand-alone product, may be stored in a computer readable storage medium. Based on such understanding, the technical solution of the present application may be substantially implemented or contributed by the prior art, or all or part of the technical solution may be embodied in a software product, which is stored in a storage medium and includes instructions for causing a computer device (which may be a personal computer, a server, a network device, or the like) or a processor (processor) to execute all or part of the steps of the method according to the embodiments of the present application. And the aforementioned storage medium includes: various media capable of storing program codes, such as a usb disk, a removable hard disk, a read-only memory (ROM), a Random Access Memory (RAM), a magnetic disk, or an optical disk.

Based on the above embodiments, the embodiments of the present application further provide a signal processing apparatus, which is used for implementing the signal processing method shown in fig. 2. The signal processing apparatus may be a transmitting end in the foregoing embodiment, and specifically may be a processor, a chip or a chip system, or a functional module in the transmitting end. Referring to fig. 20, the signal processing apparatus 2000 may include: a transceiver 2001 and a processor 2002. Optionally, the signal processing apparatus 2000 may further include a memory 2003. The memory 2003 may be disposed inside the signal processing apparatus 2000, or may be disposed outside the signal processing apparatus 2000. The processor 2002 may control the transceiver 2001 to receive and transmit signals.

Specifically, the processor 2002 may be a Central Processing Unit (CPU), a Network Processor (NP), or a combination of the CPU and the NP. The processor 2002 may further include a hardware chip. The hardware chip may be an application-specific integrated circuit (ASIC), a Programmable Logic Device (PLD), or a combination thereof. The PLD may be a Complex Programmable Logic Device (CPLD), a field-programmable gate array (FPGA), a General Array Logic (GAL), or any combination thereof.

Wherein the transceiver 2001, the processor 2002 and the memory 2003 are interconnected. Optionally, the transceiver 2001, the processor 2002 and the memory 2003 are connected to each other by a bus 2004; the bus 2004 may be a Peripheral Component Interconnect (PCI) bus, an Extended Industry Standard Architecture (EISA) bus, or the like. The bus may be divided into an address bus, a data bus, a control bus, etc. For ease of illustration, only one thick line is shown in FIG. 20, but this is not intended to represent only one bus or type of bus.

In an alternative embodiment, the memory 2003 is used to store programs and the like. In particular, the program may include program code comprising computer operating instructions. The memory 2003 may include RAM, and may also include non-volatile memory (non-volatile memory), such as one or more disk memories. The processor 2002 executes the application program stored in the memory 2003 to implement the above functions, thereby implementing the functions of the signal processing apparatus 2000.

Specifically, the processor 2002 may enable the signal processing apparatus 2000 to implement the signal processing method provided by the embodiment of the present application by performing the following operations: carrying out in-phase quadrature IQ phase rotation processing on the first signal to obtain a second signal, and determining a target signal to be sent to a receiving end based on the second signal and the third signal; the first signal is one of a signal to be modulated and a direct current signal; the third signal is a signal except the first signal in the signal to be modulated and the direct current signal.

In an optional implementation manner, when the first signal is the dc signal and the third signal is the signal to be modulated, the processor 2002 is specifically configured to, when determining a target signal based on the second signal and the third signal: and combining the second signal and the signal to be modulated into a fourth signal, and carrying out carrier modulation on the fourth signal based on a carrier signal to obtain the target signal.

In another optional implementation manner, when the first signal is the direct current signal and the third signal is the signal to be modulated, the direct current signal is obtained after modulation of a carrier signal; when determining the target signal based on the second signal and the third signal, the processor 2002 is specifically configured to: and carrying out carrier modulation on the signal to be modulated based on the carrier signal to obtain a fifth signal, and combining the fifth signal and the second signal into the target signal.

In another optional implementation manner, when the first signal is the signal to be modulated and the third signal is the dc signal, the processor 2002 is specifically configured to, when determining a target signal based on the second signal and the third signal: and combining the second signal and the direct current signal into a sixth signal, and carrying out carrier modulation on the sixth signal based on a carrier signal to obtain the target signal.

Illustratively, the target signal conforms to the following equation:

wherein, C [ n ]]Is the target signal; s [ n ]]For the signal to be modulated, the signal to be modulated is a real signal with the average value of 0; DC is the direct current signal;is a phase offset; f. of_cIs the carrier frequency.

By adopting the signal processing device in the embodiment of the application, the influence of ISI interference on the power of a received signal when the constellation point of the received signal is expanded can be changed by changing the relative rotation phase of the baseband direct current component and the signal to be modulated in the system, so that the anti-dispersion capability of the system can be improved, and the influence of dispersion on the transmitted signal can be reduced. Moreover, the anti-dispersion capability of the system is improved without depending on the equalization processing of the receiving end, and the realization complexity and difficulty of the receiving end are greatly simplified. Meanwhile, the system can bear larger channel dispersion damage than the traditional amplitude modulation-direct detection system, so that longer transmission distance is supported in the existing dispersion limited system.

Based on the above embodiments, the present application further provides a computer-readable storage medium, where the computer-readable storage medium is used to store a computer program, and when the computer program is executed by a computer, the computer may implement any one of the signal processing methods provided by the above method embodiments.

The embodiment of the present application further provides a computer program product, where the computer program product is used to store a computer program, and when the computer program is executed by a computer, the computer may implement any one of the signal processing methods provided by the foregoing method embodiments.

The embodiment of the present application further provides a chip, which includes a processor and a communication interface, where the processor is coupled with a memory, and is configured to call a program in the memory, so that the chip implements any one of the signal processing methods provided in the foregoing method embodiments.

As will be appreciated by one skilled in the art, embodiments of the present application may be provided as a method, system, or computer program product. Accordingly, the present application may take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects. Furthermore, the present application may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, and the like) having computer-usable program code embodied therein.

The present application is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems), and computer program products according to the application. It will be understood that each flow and/or block of the flow diagrams and/or block diagrams, and combinations of flows and/or blocks in the flow diagrams and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.

These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instruction means which implement the function specified in the flowchart flow or flows and/or block diagram block or blocks.

These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.

It will be apparent to those skilled in the art that various changes and modifications may be made in the present application without departing from the scope of the application. Thus, if such modifications and variations of the present application fall within the scope of the claims of the present application and their equivalents, the present application is intended to include such modifications and variations as well.