阅读说明：本技术 一种适用于π/4-DQPSK的载波跟踪方法、设备及可读存储介质 (Carrier tracking method and device suitable for pi/4-DQPSK and readable storage medium ) 是由 聂晟昱 李志强 于 2021-08-18 设计创作，主要内容包括：本发明公开了一种适用于π/4-DQPSK的载波跟踪方法、设备及可读存储介质,该方法包括接收采样处理、两路解调判决和载波环路跟踪,接收来自发送端的π/4-DQPSK调制射频信号,利用正交的本地载波分别与所述数字中频信号进行I路解调处理和Q路解调处理,I路解调处理中经过点积运算后的结果,与Q路解调处理中经过差积运算后的结果,结合用于相位误差检测,并经过环路滤波后,跟踪调控本地载波。本发明有利于降低调制信号包络起伏,解调方法通过全数字化处理方式,实现了对π/4-DQPSK调制信号的解调转换并有效解调出信息,同时还具有很好的载波跟踪能力,抗噪声特性好。(The invention discloses a carrier tracking method, equipment and a readable storage medium suitable for pi/4-DQPSK, wherein the method comprises the steps of receiving sampling processing, two-path demodulation judgment and carrier loop tracking, receiving a pi/4-DQPSK modulated radio frequency signal from a transmitting end, and utilizing orthogonal local carriers to respectively carry out I-path demodulation processing and Q-path demodulation processing with a digital intermediate frequency signal, wherein a result after dot product operation in the I-path demodulation processing and a result after difference product operation in the Q-path demodulation processing are combined for phase error detection and are subjected to loop filtering to track and regulate the local carriers. The invention is beneficial to reducing the envelope fluctuation of the modulation signal, the demodulation method realizes the demodulation conversion of the pi/4-DQPSK modulation signal and effectively demodulates the information by a full digitalization processing mode, and simultaneously, the invention also has good carrier tracking capability and good noise resistance.)

1. A carrier tracking method applicable to pi/4-DQPSK, comprising the steps of:

receiving sampling processing, namely receiving a pi/4-DQPSK modulated radio frequency signal from a transmitting end, wherein the pi/4-DQPSK modulated radio frequency signal can obtain an intermediate frequency signal through down-conversion, and the intermediate frequency signal is subjected to band-pass filtering and then AD sampling to obtain a digital intermediate frequency signal;

two paths of demodulation judgment, namely performing I path demodulation processing and Q path demodulation processing on the digital intermediate frequency signals by utilizing orthogonal local carriers; the I path demodulation processing comprises in-phase local carrier multiplication, baseband shaping filtering, dot product operation, in-phase differential solution and judgment, and the Q path demodulation processing comprises quadrature carrier multiplication, baseband shaping filtering, differential product operation, quadrature differential solution and judgment;

and tracking a carrier loop, wherein a result obtained after dot product operation in the I path demodulation processing and a result obtained after difference product operation in the Q path demodulation processing are combined for phase error detection, and a local carrier is tracked and regulated after loop filtering.

2. The carrier tracking method for pi/4-DQPSK according to claim 1, wherein said pi/4-DQPSK modulated radio frequency signal from the transmitting end generating step comprises:

converting the transmitted data, converting the transmitted data into two parallel data sequences corresponding to the in-phase channel data sequence a by one serial data sequence through serial-to-parallel conversion_kAnd orthogonal channel data sequence b_kK represents the serial number of data;

differential phase encoding using said in-phase channel data sequence a_kAnd orthogonal channel data sequence b_kCarrying out differential phase transformation to obtain a phase difference between a front code element and a rear code element, and respectively calculating by using the phase difference to obtain an in-phase channel modulation sequence u_k(t) and an orthogonal channel modulation sequence v_k(t)；

Signal modulation, said in-phase channel modulation sequence u_k(t) and an orthogonal channel modulation sequence v_kAnd (t) respectively carrying out shaping filtering, multiplying the filtered signals respectively by orthogonal originating carriers, and then adding the multiplied signals to obtain the pi/4-DQPSK modulated radio frequency signal.

3. The carrier tracking method applied to pi/4-DQPSK according to claim 2,

calculating according to the phase difference of the front and rear code elements to obtain the in-phase channel modulation sequence u_k(t) and the orthogonal channel modulation sequence v_k(t) are respectively:

u_k(t)＝u_k-1(t)cos(Δθ_k)-v_k-1(t)sin(Δθ_k)

v_k(t)＝u_k-1(t)sin(Δθ_k)+v_k-1(t)cos(Δθ_k)，

where Δ θ_kRepresenting the front-to-back symbol phase difference.

4. The carrier tracking method applied to pi/4-DQPSK according to claim 3,

the in-phase local carrier wave multiplication in the I path demodulation processing obtains I path data I_k＝cos(φ_k+θ_k) Obtaining a base band pi/4-DQPSK in-phase component through the base band forming filtering, and carrying out dot product operation to obtain a result that the base band DQPSK in-phase component W is_k；

Q path data obtained by multiplying the in-phase local carrier in the Q path demodulation processing is Q_k＝sin(φ_k+θ_k) Obtaining a base band pi/4-DQPSK orthogonal component through the base band forming filtering, and carrying out the difference product operation to obtain a result that the base band DQPSK orthogonal component Z is obtained_k；

Wherein phi is_kFor modulating the phase, θ, by a carrier_kIs the phase error.

5. The carrier tracking method applied to pi/4-DQPSK according to claim 4,

the dot product operation is as follows:

DOT_k＝(i_k+q_k)·i_k-1+(i_k-q_k)·q_k-1；

the difference product operation is:

CROSS_k＝(i_k-q_k)·i_k-1-(i_k+q_k)·q_k-1。

6. the carrier tracking method applied to pi/4-DQPSK according to claim 5,

the baseband DQPSK in-phase component W_kAnd basebandDQPSK quadrature component Z_kAnd performing combined calculation to obtain an expression of phase error detection as follows:

U_d＝DOT_K·(DOT_K-CROSS_K)·CROSS_K·(DOT_K+CROSS_K)；

will the error U_dThe local carrier wave is input into a loop filter to correct the local carrier wave frequency and then input into a numerical control oscillator to recover the local carrier wave in real time.

7. The carrier tracking method applied to pi/4-DQPSK according to claim 5,

the in-phase demodulation in the I-path demodulation processing comprises the following steps:

X_k＝W_kW_k-1+Z_kZ_k-1＝cos(θ_k-θ_k-1)＝cos(Δθ_k)；

the quadrature demodulation in the Q-path demodulation process is:

Y_k＝Z_kW_k-1-W_kZ_k-1＝sin(θ_k-θ_k-1)＝sin(Δθ_k)。

8. the carrier tracking method applied to pi/4-DQPSK according to claim 7, wherein the decision in the I-path demodulation process and the decision in the Q-path demodulation process correspond to:

9. a carrier tracking apparatus adapted for pi/4-DQPSK, characterized in that the carrier tracking apparatus adapted for pi/4-DQPSK comprises a memory, a processor and a carrier tracking program adapted for pi/4-DQPSK stored on the memory and executable on the processor, the carrier tracking program of pi/4-DQPSK being executed by the processor implementing the steps of the carrier tracking method adapted for pi/4-DQPSK as claimed in any of claims 1 to 8.

10. A readable storage medium, having stored thereon a carrier tracking program adapted for pi/4-DQPSK, the carrier tracking program adapted for pi/4-DQPSK being executed by a processor to implement the steps of the carrier tracking method adapted for pi/4-DQPSK according to any of claims 1-8.

Technical Field

The present application relates to the field of mobile and satellite communications technologies, and in particular, to a carrier tracking method and device suitable for pi/4-DQPSK, and a readable storage medium.

Background

In the technical field of mobile communication and satellite communication, a signal modulation mode is selected to be matched with the channel characteristics of signal transmission, and a modulation signal suitable for channel transmission is obtained. In the prior art, the maximum phase jump of a QPSK signal modulation mode is pi, the spectral envelope fluctuation is large, and the spectral distortion generated by nonlinear amplification is easily caused.

In addition, in the QPSK signal modulation scheme, the degradation of demodulation performance is more seriously affected as the frequency difference increases during the synchronization of the received carrier. Therefore, there is a need for an improved signal modulation and reception method to reduce and eliminate the deterioration of demodulation performance due to frequency difference and improve the anti-noise performance of signal reception.

Disclosure of Invention

Based on this, the embodiments of the present invention provide a carrier tracking method, device and readable storage medium suitable for pi/4-DQPSK, which solve the problem of spectrum distortion caused by a large spectrum envelope waveguide in the prior art for pi/4-DQPSK modulation signal reception and demodulation, and overcome the problem of demodulation performance degradation caused by increased frequency difference.

In order to solve the above technical problem, an embodiment of the present application provides a carrier tracking method suitable for pi/4-DQPSK, and a specific technical solution is as follows:

receiving sampling processing, namely receiving a pi/4-DQPSK modulated radio frequency signal from a transmitting end, wherein the pi/4-DQPSK modulated radio frequency signal can obtain an intermediate frequency signal through down-conversion, and the intermediate frequency signal is subjected to band-pass filtering and then AD sampling to obtain a digital intermediate frequency signal; two paths of demodulation judgment, namely performing I path demodulation processing and Q path demodulation processing on the digital intermediate frequency signals by utilizing orthogonal local carriers; the I path demodulation processing comprises in-phase local carrier multiplication, baseband shaping filtering, dot product operation, in-phase differential solution and judgment, and the Q path demodulation processing comprises quadrature carrier multiplication, baseband shaping filtering, differential product operation, quadrature differential solution and judgment; and tracking a carrier loop, wherein a result obtained after dot product operation in the I path demodulation processing and a result obtained after difference product operation in the Q path demodulation processing are combined for phase error detection, and a local carrier is tracked and regulated after loop filtering.

Preferably, the step of generating the pi/4-DQPSK-modulated radio frequency signal from the transmitting end includes:

converting the transmitted data, converting the transmitted data into two parallel data sequences corresponding to the in-phase channel data sequence a by one serial data sequence through serial-to-parallel conversion_kAnd orthogonal channel data sequence b_kK represents the serial number of data;differential phase encoding using said in-phase channel data sequence a_kAnd orthogonal channel data sequence b_kCarrying out differential phase transformation to obtain a phase difference between a front code element and a rear code element, and respectively calculating by using the phase difference to obtain an in-phase channel modulation sequence u_k(t) and an orthogonal channel modulation sequence v_k(t); signal modulation, said in-phase channel modulation sequence u_k(t) and an orthogonal channel modulation sequence v_kAnd (t) respectively carrying out shaping filtering, multiplying the filtered signals respectively by orthogonal originating carriers, and then adding the multiplied signals to obtain the pi/4-DQPSK modulated radio frequency signal.

Preferably, the in-phase channel modulation sequence u is obtained by calculating according to the phase difference between the front and rear code elements_k(t) and the orthogonal channel modulation sequence v_k(t) are respectively:

where Δ θ_kRepresenting the front-to-back symbol phase difference.

Preferably, the I-path data obtained by multiplying the in-phase local carrier in the I-path demodulation processing is I_k＝cos(φ_k+θ_k) Obtaining a base band pi/4-DQPSK in-phase component through the base band forming filtering, and carrying out dot product operation to obtain a result that the base band DQPSK in-phase component W is_k(ii) a Q path data obtained by multiplying the in-phase local carrier in the Q path demodulation processing is Q_k＝sin(φ_k+θ_k) Obtaining a base band pi/4-DQPSK orthogonal component through the base band forming filtering, and carrying out the difference product operation to obtain a result that the base band DQPSK orthogonal component Z is obtained_k(ii) a Wherein phi is_kFor modulating the phase, θ, by a carrier_kIs the phase error.

Preferably, the dot product operation is:

DOT_k＝(i_k+q_k)·i_k-1+(i_k-q_k)·q_k-1；

the difference product operation is:

CROSS_k＝(i_k-q_k)·i_k-1-(i_k+q_k)·q_k-1。

preferably, the baseband DQPSK in-phase component W is divided into two parts_kAnd baseband DQPSK quadrature component Z_kPerforming a combined calculation to obtain an expression of phase error detection as

U_d＝DOT_K·(DOT_K-CROSS_K)·CROSS_K·(DOT_K+CROSS_K)；

Will the error U_dThe local carrier wave is input into a loop filter to correct the local carrier wave frequency and then input into a numerical control oscillator to recover the local carrier wave in real time.

Preferably, the in-phase demodulation in the I-path demodulation process is divided into:

X_k＝W_kW_k-1+Z_kZ_k-1＝cos(θ_k-θ_k-1)＝cos(Δθ_k)；

the quadrature demodulation in the Q-path demodulation process is:

Y_k＝Z_kW_k-1-W_kZ_k-1＝sin(θ_k-θ_k-1)＝sin(Δθ_k)。

preferably, the decision in the I-path demodulation processing and the decision in the Q-path demodulation processing correspond to:

preferably, another embodiment of the present invention provides a carrier tracking device suitable for pi/4-DQPSK, where the carrier tracking device suitable for pi/4-DQPSK includes a memory, a processor, and a carrier tracking program suitable for pi/4-DQPSK stored in the memory and executable on the processor, and the carrier tracking program suitable for pi/4-DQPSK implements the steps of the method proposed by the above embodiment when executed by the processor.

Preferably, another embodiment of the present invention provides a readable storage medium, which stores thereon a carrier tracking program adapted for pi/4-DQPSK, and when executed by a processor, implements the steps of the method proposed by the above embodiment.

The embodiment of the application has the following beneficial effects: the invention discloses a carrier tracking method, equipment and a readable storage medium suitable for pi/4-DQPSK, wherein the method comprises the steps of receiving sampling processing, two-path demodulation judgment and carrier loop tracking, receiving a pi/4-DQPSK modulated radio frequency signal from a transmitting end, and utilizing orthogonal local carriers to respectively carry out I-path demodulation processing and Q-path demodulation processing with a digital intermediate frequency signal, wherein a result after dot product operation in the I-path demodulation processing and a result after difference product operation in the Q-path demodulation processing are combined for phase error detection and are subjected to loop filtering to track and regulate the local carriers. The invention is beneficial to reducing the envelope fluctuation of the modulation signal, the demodulation method realizes the demodulation conversion of the pi/4-DQPSK modulation signal and effectively demodulates the information by a full digitalization processing mode, and simultaneously, the invention also has good carrier tracking capability and good noise resistance.

Drawings

In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present application, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.

FIG. 1 is a flowchart of an embodiment of a carrier tracking method for π/4-DQPSK according to the present invention;

FIG. 2 is a modulation block diagram of a transmitting end in another embodiment of the carrier tracking method applicable to π/4-DQPSK according to the present invention;

FIG. 3 is a receiving end receiving demodulation block diagram in another embodiment of the carrier tracking method applicable to π/4-DQPSK according to the present invention;

FIG. 4 is a carrier tracking simulation diagram of another embodiment of the carrier tracking method applicable to π/4-DQPSK according to the present invention;

fig. 5 is a schematic structural diagram of a carrier tracking apparatus suitable for pi/4-DQPSK in a hardware operating environment according to an embodiment of the present invention.

Detailed Description

The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are only a part of the embodiments of the present application, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.

The terms "comprising" and "having," and any variations thereof, as appearing in the specification, claims and drawings of this application, are intended to cover non-exclusive inclusions. For example, a process, method, system, article, or apparatus that comprises a list of steps or modules is not limited to the listed steps or elements but may alternatively include other steps or elements not expressly listed or inherent to such process, method, article, or apparatus. Furthermore, the terms "first," "second," and "third," etc. are used to distinguish between different objects and are not used to describe a particular order.

For a better understanding of the above technical solutions, exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be embodied in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.

As shown in fig. 1, fig. 1 is a flowchart of an embodiment of a carrier tracking method applicable to pi/4-DQPSK in the present invention, in which the carrier tracking method applicable to pi/4-DQPSK includes the following steps:

step S1, receiving sampling processing, namely receiving a pi/4-DQPSK modulated radio frequency signal from a transmitting end, wherein the pi/4-DQPSK modulated radio frequency signal can obtain an intermediate frequency signal through down-conversion, and the intermediate frequency signal is subjected to band-pass filtering and then AD sampling to obtain a digital intermediate frequency signal;

step S2, two paths of demodulation judgment, namely, I path demodulation processing and Q path demodulation processing are respectively carried out on the digital intermediate frequency signals by utilizing orthogonal local carriers; the I path demodulation processing comprises in-phase local carrier multiplication, baseband shaping filtering, dot product operation, in-phase differential solution and judgment, and the Q path demodulation processing comprises quadrature carrier multiplication, baseband shaping filtering, differential product operation, quadrature differential solution and judgment;

and step S3, tracking and regulating the local carrier by the carrier loop, wherein the result after dot product operation in the I-path demodulation processing and the result after difference product operation in the Q-path demodulation processing are combined for phase error detection and are filtered by the loop.

Communication technology has developed to present day, and a plurality of communication systems are available, and different communication systems can be selected according to different environments and specific situations. Since the spectrum characteristic of the baseband signal is not suitable for channel transmission, frequency conversion modulation is required to obtain a signal suitable for channel transmission. The maximum phase jump of the traditional QPSK modulation signal is pi, and the amplitude of the spectral envelope fluctuation is large. The pi/4-DQPSK is fully called pi/4-Shift differential Encoded Quadrature Phase Shift Keying, and is an improved modulation mode based on QPSK, and the maximum Phase jump of the pi/4-DQPSK modulated radio frequency signal can be realized at a transmitting end by only 3 pi/4 through the embodiment of the carrier tracking method suitable for the pi/4-DQPSK, so that the spectrum distortion generated by the envelope fluctuation and nonlinear amplification of the modulated signal is obviously reduced, and the spectrum characteristic is better.

Preferably, since pi/4-DQPSK adopts differential coding, the invention uses carrier tracking and needs carrier recovery during the receiving process. In addition, in the received carrier synchronization, if there is a frequency difference Δ f between the frequency of the local oscillator and the carrier frequency of the signal, there will be a phase shift of 2 pi Δ fT within one symbol, which will increase the bit error rate of the system, and when Δ fT is 0.025, i.e., the frequency deviation is 2.5% of the symbol rate, there will be a frequency difference Δ f within one symbol periodA 9 DEG phase difference at a bit error rate of 10^-5This phase difference causes performance deterioration of about 1dB, and the performance deterioration is more affected as the frequency difference increases. Therefore, when the system is implemented, measures are taken to reduce the frequency difference between the frequency of the local oscillator and the signal carrier frequency, and the invention adopts a carrier tracking method suitable for pi/4-DQPSK to eliminate the performance deterioration caused by the frequency difference and improve the anti-noise performance of the system.

Preferably, referring to step S1, in conjunction with fig. 2, fig. 2 is a modulation block diagram of a transmitting end in an embodiment of the carrier tracking method applicable to pi/4-DQPSK in accordance with the present invention. Specifically, the method for generating the pi/4-DQPSK modulation radio frequency signal of the transmitting end comprises the following steps:

step S11, the transmitted data is converted from serial to parallel, and one serial data sequence is converted into two parallel data sequences corresponding to the same-phase channel data sequence a_kAnd orthogonal channel data sequence b_kK represents the serial number of data;

step S12 of differential phase encoding using the in-phase channel data sequence a_kAnd orthogonal channel data sequence b_kCarrying out differential phase transformation to obtain a phase difference between a front code element and a rear code element, and respectively calculating by using the phase difference to obtain an in-phase channel modulation sequence u_k(t) and an orthogonal channel modulation sequence v_k(t)；

Step S13, signal modulation, the in-phase channel modulation sequence u_k(t) and an orthogonal channel modulation sequence v_kAnd (t) respectively carrying out shaping filtering, multiplying the filtered signals respectively by orthogonal originating carriers, and then adding the multiplied signals to obtain the pi/4-DQPSK modulated radio frequency signal.

Preferably, referring to step S11 and referring to fig. 2, data is input at the transmitting end, the input data is converted in serial-to-parallel by serial-to-parallel conversion unit 101, and serial-to-parallel conversion unit 101 converts the input one-way serial data sequence (a)₁b₁a₂b₂…a_kb_k…) into two parallel data sequences, which are respectively the in-phase channel data sequence a_kAnd orthogonal channel data sequence b_kAnd k represents the sequence number of data.

Preferably, with respect to step S12 and in conjunction with fig. 2, the two-way parallel data sequence output by the serial/parallel conversion unit 101 is: in-phase channel data sequence a_kAnd orthogonal channel data sequence b_kInput to the signal conversion section 102 to perform differential phase conversion to obtain a front-to-back symbol phase difference Δ θ_kAnd then the phase difference Delta theta between the front and rear code elements is used_kRespectively calculating to obtain in-phase channel modulation sequences u_k(t) and an orthogonal channel modulation sequence v_k(t) and output.

Preferably, the in-phase channel data sequence a_kAnd orthogonal channel data sequence b_kAn implementation method for obtaining the phase difference between the front and rear code elements by performing differential phase transformation is shown in table 1, and the table 1 is a pi/4-DQPSK differential phase transformation method.

TABLE 1 Pi/4-DQPSK differential phase transformation method

In-phase branch ak	Quadrature branch bk	Front-to-back symbol phase difference Δ θk
			1	1	π/4
0	1	3π/4
			0	0	-3π/4
1	0	-π/4

More preferably, Table 1 is but one preferred embodiment, with a phase difference Δ θ between the previous and subsequent symbols_kWith an in-phase channel data sequence a_kAnd orthogonal channel data sequence b_kThe value combination of (1) can also have other corresponding relations, which are all included in the protection scope of the application, as shown in table 2, table 2 is another conversion method of pi/4-DQPSK differential phase.

TABLE 2 π/4-DQPSK differential phase alternative transformation method

In-phase branch ak	Quadrature branch bk	Front-to-back symbol phase difference Δ θk
			1	1	3π/4
0	1	π/4
			0	0	-π/4
1	0	-3π/4

In practical application, only one of the transformation methods needs to be determined for use, and correspondingly, the transformation method specifically adopted by the sending end needs to be confirmed at the receiving end. It can be seen that after the data at the transmitting end is modulated by pi/4-DQPSK, the phase jump is only:

{ pi/4, 3 pi/4, -pi/4 }, the maximum phase jump of which is 3 pi/4, thereby being capable of enabling the spectral distortion generated by the envelope fluctuation and the nonlinear amplification of the modulation signal to be remarkably reduced and having better spectral characteristics.

Preferably, a front-to-back symbol phase difference Δ θ is obtained_kThen, the front-to-back symbol phase difference Δ θ can be further utilized_kRespectively calculating to obtain in-phase channel modulation sequences u_k(t) and an orthogonal channel modulation sequence v_k(t)：

u_k(t)＝u_k-1(t)cos(Δθ_k)-v_k-1(t)sin(Δθ_k)，

v_k(t)＝u_k-1(t)sin(Δθ_k)+v_k-1(t)cos(Δθ_k)。

Preferably, regarding step S13, in conjunction with fig. 2, the in-phase channel modulation sequence u output by the signal conversion unit 102 is_k(t) and an orthogonal channel modulation sequence v_k(t) are inputted to first baseband shaping filter 1031 and second baseband shaping filter 1032, respectively, and shaped and filtered, and in-phase channel modulation sequence u is obtained_k(t) and an orthogonal channel modulation sequence v_k(t) after shaping and filtering, multiplying the carriers respectively with orthogonal originating carriers, and adding the multiplied carriers, wherein the originating carriers are divided into two orthogonal paths of outputs which correspond to cos w respectively_ct and sinw_ct, one-path originating carrier cos w_ct is multiplied by the waveform signal output from the first baseband shaping filter 1031 through the first multiplier 1041, and the other path of the originating carrier sinw_ct is multiplied by the waveform signal output from the second baseband shaping filter 1032 by a second multiplier 1042. Then, the user can use the device to perform the operation,the results output by the first multiplier 1041 and the second multiplier 1042 are added by the adder 105 to obtain a pi/4-DQPSK modulated radio frequency signal finally generated by modulation.

The above description is about the specific implementation process of step S1 in fig. 1 at the originating end, and the following description is about the specific demodulation and reception process at the receiving end.

Preferably, regarding step S2, as shown in fig. 3 in conjunction with fig. 3, the I-path demodulation process includes an in-phase multiplier 2011, an in-phase baseband shaping filter 2021, a dot product operator 2031, an in-phase difference calculator 2041 and an in-phase decision unit 2051, which respectively perform in-phase local carrier multiplication, baseband shaping filtering, dot product operation, in-phase solution difference and decision; the Q-path demodulation process includes an orthogonal multiplier 2012, an orthogonal baseband shaping filter 2022, a difference product calculator 2032, an orthogonal phase difference calculator 2042, and an orthogonal decision unit 2052, and performs orthogonal carrier multiplication, baseband shaping filtering, difference product calculation, orthogonal de-differentiation, and decision, respectively.

Preferably, the received I-way data is I_k＝cos(φ_k+θ_k) Obtaining the base band pi/4-DQPSK in-phase component through base band forming filtering, carrying out dot product operation to obtain phi_kThe result of the cancellation is a baseband DQPSK in-phase component W_k(ii) a The received Q path data is Q_k＝sin(φ_k+θ_k) Obtaining a base band pi/4-DQPSK orthogonal component through base band forming filtering, carrying out a difference product operation, and converting phi into phi_kCancellation, the result being the baseband DQPSK quadrature component Z_k(ii) a Wherein phi is_kFor modulating the phase, θ, by a carrier_kIs the phase error.

Respectively performing DOT product operation DOT based on the I path data and the Q path data_kCROSS operation of sum and difference_kCalculating to obtain:

DOT_k＝i_k·i_k-1+q_k·q_k-1＝cos(Δφ_k+Δθ_k)

CROSS_k＝q_k·i_k-1-i_k·q_k-1＝sin(Δφ_k-Δθ_k)

wherein is delta phi_kThe variation of the carrier modulation phase at the front and rear time points is taken as

A phase difference delta theta between symbols before and after { pi/4, 3 pi/4, 5 pi/4, 7 pi/4 }_kTo obtain this change in phase difference, it is necessary to eliminate Δ φ_kIn order to eliminate the influence of delta phi_kDOT product operation DOT_kCROSS operation of sum and difference_kThe calculation can be further expressed as:

DOT_k＝(i_k+q_k)·i_k-1+(i_k-q_k)·q_k-1

＝cos(φ_k+φ_k-1+θ_k+θ_k-1)+sin(φ_k+φ_k-1+θ_k+θ_k-1)

CROSS_k＝(i_k-q_k)·i_k-1-(i_k+q_k)·q_k-1

＝cos(φ_k+φ_k-1+θ_k+θ_k-1)-sin(φ_k+φ_k-1+θ_k+θ_k-1)

preferably, referring to fig. 3 for step S3, as shown in fig. 3, the I-path demodulation process includes a dot product operator 2031 and a difference product operator 2032, the result processed by the dot product operator 2031 and the difference product operator 2032 is input to the phase error detector 206 for phase error detection, then loop filtering is performed by the loop filter 207, and two orthogonal local carriers are generated and output by the numerically controlled oscillator 208(NCO), wherein one local carrier is cos w_ct is input to an in-phase multiplier 2011 for down-conversion of an in-phase carrier, and the other local carrier sinw_ct is input to an in-phase multiplier 2012 to be down-converted to a quadrature carrier. Specifically, the phase error detection step includes:

step 31, the baseband DQPSK in-phase component W_kAnd baseband DQPSK quadrature component Z_kAnd performing combined calculation to obtain an expression of phase error detection as follows:

U_d＝DOT_K·(DOT_K-CROSS_K)·CROSS_K·(DOT_K+CROSS_K)；

step S32, converting the error U_dThe local carrier wave is input into a loop filter to correct the local carrier wave frequency and then input into a numerical control oscillator to recover the local carrier wave in real time.

Preferably, referring to fig. 3, it can be seen from fig. 3 that the phase error detector 206 implements a phase error detection process to obtain the error U_d：

U_d＝DOT_K·(DOT_K-CROSS_K)·CROSS_K·(DOT_K+CROSS_K)

DOT based on the DOT product operation_kCROSS operation of sum and difference_kFurther obtaining:

U_d＝{cos(φ_k+φ_k-1+θ_k+θ_k-1)+sin(φ_k+φ_k-1+θ_k+θ_k-1)}·2sin(φ_k+φ_k-1+θ_k+θ_k-1)·

{cos(φ_k+φ_k-1+θ_k+θ_k-1)-sin(φ_k+φ_k-1+θ_k+θ_k-1)}·2cos(φ_k+φ_k-1+θ_k+θ_k-1)

＝sin[4(φ_k+φ_k-1+θ_k+θ_k-1)]

namely: u shape_d＝sin[4(φ_k+φ_k-1+θ_k+θ_k-1)]

Wherein phi_k，φ_k-1For modulating the phase, theta, of the carrier of preceding and following symbols_k,θ_k-1Is the phase of the preceding and following code elements, and the sum phi of the carrier modulation phases at the preceding and following moments_k+φ_k-1The values of (a) are equivalent to: { π/4, 3 π/4, 5 π/4, 7 π/4}, and therefore, can be finally simplified as:

U_d＝-sin[4(θ_k+θ_k-1)]≈-sin(θ_error)

after processing by the phase error detector 206, the resulting signal U_dOnly the phase error theta is included_errorThe modulation information in the received signal is completely removed. Then, the error signal is subjected to loop filtering through a loop filter 207, and two paths of orthogonal local carriers are generated through a numerically controlled oscillator 208 and are respectively used for carrier synchronization tracking of an in-phase branch and an orthogonal branch, so that the local carriers can be recovered in real time.

Preferably, after the local carrier synchronization at the receiving end, the synchronized value is:

to this end, we have obtained a DQPSK signal without frequency difference, the information being also contained in the phase difference. Specifically, the in-phase demodulation in the I-path demodulation process includes:

X_k＝W_kW_k-1+Z_kZ_k-1＝cos(θ_k-θ_k-1)＝cos(Δθ_k)；

the quadrature demodulation in the Q-path demodulation process is:

Y_k＝Z_kW_k-1-W_kZ_k-1＝sin(θ_k-θ_k-1)＝sin(Δθ_k)。

preferably, referring to fig. 3, as shown in fig. 3, the in-phase difference calculator 2041 de-differentiates the demodulated signal in the I-path demodulation process, so as to obtain the signalSubstituting the same-phase solution difference to obtain:

X_k＝W_kW_k-1+Z_kZ_k-1＝cos(θ_k-θ_k-1)＝cos(Δθ_k)

preferably, referring to fig. 3, as shown in fig. 3, the demodulated signal in the Q-path demodulation process is de-differentiated by the quadrature phase difference calculator 2042, so as to obtain the differenceSubstituting the orthogonal solution difference to obtain:

Y_k＝Z_kW_k-1-W_kZ_k-1＝sin(θ_k-θ_k-1)＝sin(Δθ_k)

preferably, X_kAnd Y_kThe polarity determination rule of (1) is shown in table 3, and table 3 is a DQPSK signal demodulation determination rule.

TABLE 3DQPSK signal demodulation decision rule

XkPolarity of road	YkPolarity of road	Phase difference Δ θ	Decision output I path	Decision output Q path
					Is just	Is just	0	1	1
Negative pole	Is just	π/2	0	1
					Negative pole	Negative pole	π	0	0
Is just	Negative pole	3π/2	1	0

Preferably, according to table 3, the following decision methods are used to respectively decide the result after the in-phase difference calculator in the I-path demodulation process and the result after the quadrature phase difference calculator in the Q-path demodulation process, and the results are:

to this end, for X_kAnd Y_kThe original information can be recovered by the judgment.

Therefore, the invention realizes the DQPSK modulation based on pi/4 phase at the transmitting end based on the corresponding relation in the table 1, the maximum phase jump is 3 pi/4, and the invention has smaller envelope fluctuation. In the receiving end processing process, firstly, the band-pass filtering is carried out on the intermediate frequency signal of AD sampling, the intermediate frequency signal is respectively multiplied by the in-phase component and the orthogonal component of the carrier wave, and then the DOT product DOT of I-path demodulation is calculated_kDifference product CROSS of sum Q demodulation_kCombining the result of dot product operation in I path demodulation process with the result of difference product operation in Q path demodulation process, and processing by phase error detector to obtain signal U_dOnly the phase error theta is included_errorThe error signal is subjected to loop filtering through a loop filter, two paths of orthogonal local carriers are generated through a numerical control oscillator and are respectively used for carrier synchronous tracking of an in-phase branch and an orthogonal branch, and the demodulated local carriers are used for carrying out synchronous tracking on the in-phase branch and the orthogonal branchAfter the signals are subjected to de-differentiation, X is subjected to decision rule pair_kAnd Y_kAnd the original information can be recovered by judging.

In order to verify the technical effect of the invention, simulation verification is carried out, and the simulation parameter is that the sampling rate is f_s80MHz, carrier frequency f_cThe rate of the information symbols is 4Kbit/s, the frequency difference is 200Hz, the tracked frequency difference is shown in fig. 4, and it can be seen from fig. 4 that the loop can normally lock to the frequency difference of the carrier, and the correctness of the scheme is verified.

In addition, the invention also provides a carrier tracking device of pi/4-DQPSK, the carrier tracking device of pi/4-DQPSK comprises a memory, a processor and a carrier tracking program of pi/4-DQPSK stored on the memory and capable of running on the processor, and the carrier tracking program of pi/4-DQPSK realizes the steps of the carrier tracking method suitable for pi/4-DQPSK when being executed by the processor.

Preferably, the present invention further provides a readable storage medium, on which a carrier tracking program for pi/4-DQPSK is stored, the carrier tracking program for pi/4-DQPSK being executed by a processor to implement the steps of the carrier tracking method applicable to pi/4-DQPSK as described above.

As shown in fig. 5, fig. 5 is a schematic structural diagram of a carrier tracking apparatus suitable for pi/4-DQPSK in a hardware operating environment according to an embodiment of the present invention.

The carrier tracking equipment structure applicable to the pi/4-DQPSK in the embodiment of the invention can be communication equipment.

As shown in fig. 5, the carrier tracking apparatus adapted for pi/4-DQPSK may include: a processor 1001, such as a CPU, a network interface 1004, a user interface 1003, a memory 1005, a communication bus 1002. Wherein a communication bus 1002 is used to enable connective communication between these components. The user interface 1003 may include a Display screen (Display), an input unit such as a Keyboard (Keyboard), and the optional user interface 1003 may also include a standard wired interface, a wireless interface. The network interface 1004 may optionally include a standard wireless interface (e.g., a WI-FI interface). The memory 1005 may be a high-speed RAM memory or a non-volatile memory (e.g., a magnetic disk memory). The memory 1005 may alternatively be a storage device separate from the processor 1001.

Those skilled in the art will appreciate that the carrier tracking apparatus architecture shown in fig. 5 that is suitable for pi/4-DQPSK is not intended to be limiting of carrier tracking apparatuses suitable for pi/4-DQPSK, and may include more or fewer components than shown, or some components in combination, or a different arrangement of components. The carrier tracking apparatus of the present embodiment adapted to pi/4-DQPSK is described below with reference to fig. 5.

As shown in fig. 5, the memory 1005, which is a readable storage medium, may include therein an operating system, a network communication module, a user interface module, and a carrier tracking program applicable to pi/4-DQPSK.

In the device shown in fig. 5, the network interface 1004 is mainly used for connecting to a backend server and performing data communication with the backend server; the user interface 1003 is mainly used for connecting a client (user side) and performing data communication with the client; the processor 1001 is the control center of the terminal equipment, connects the various parts of the entire carrier tracking equipment adapted for pi/4-DQPSK using various interfaces and lines, by running or executing software programs and/or modules stored in the memory 1005, and calling the carrier tracking program adapted for pi/4-DQPSK stored in the memory 1005, and performs the following operations:

receiving sampling processing, namely receiving a pi/4-DQPSK modulated radio frequency signal from a transmitting end, wherein the pi/4-DQPSK modulated radio frequency signal can obtain an intermediate frequency signal through down-conversion, and the intermediate frequency signal is subjected to band-pass filtering and then AD sampling to obtain a digital intermediate frequency signal; two paths of demodulation judgment, namely performing I path demodulation processing and Q path demodulation processing on the digital intermediate frequency signals by utilizing orthogonal local carriers; the I path demodulation processing comprises in-phase local carrier multiplication, baseband shaping filtering, dot product operation, in-phase differential solution and judgment, and the Q path demodulation processing comprises quadrature carrier multiplication, baseband shaping filtering, differential product operation, quadrature differential solution and judgment; and tracking a carrier loop, wherein a result obtained after dot product operation in the I path demodulation processing and a result obtained after difference product operation in the Q path demodulation processing are combined for phase error detection, and a local carrier is tracked and regulated after loop filtering.

Preferably, the step of generating the pi/4-DQPSK-modulated radio frequency signal from the transmitting end includes:

converting the transmitted data, converting the transmitted data into two parallel data sequences corresponding to the in-phase channel data sequence a by one serial data sequence through serial-to-parallel conversion_kAnd orthogonal channel data sequence b_kK represents the serial number of data; differential phase encoding using said in-phase channel data sequence a_kAnd orthogonal channel data sequence b_kCarrying out differential phase transformation to obtain a phase difference between a front code element and a rear code element, and respectively calculating by using the phase difference to obtain an in-phase channel modulation sequence u_k(t) and an orthogonal channel modulation sequence v_k(t); signal modulation, said in-phase channel modulation sequence u_k(t) and an orthogonal channel modulation sequence v_kAnd (t) respectively carrying out shaping filtering, multiplying the filtered signals respectively by orthogonal originating carriers, and then adding the multiplied signals to obtain the pi/4-DQPSK modulated radio frequency signal.

Preferably, the in-phase channel modulation sequence u is obtained by calculating according to the phase difference between the front and rear code elements_k(t) and the orthogonal channel modulation sequence v_k(t) are respectively:

where Δ θ_kRepresenting the front-to-back symbol phase difference.

Preferably, the I-path data obtained by multiplying the in-phase local carrier in the I-path demodulation processing is I_k＝cos(φ_k+θ_k) Obtaining a base band pi/4-DQPSK in-phase component through the base band forming filtering, and carrying out dot product operation to obtain a result that the base band DQPSK in-phase component W is_k(ii) a Q path data obtained by multiplying the in-phase local carrier in the Q path demodulation processing is Q_k＝sin(φ_k+θ_k) By said baseband shaping filteringObtaining a base band pi/4-DQPSK orthogonal component, and carrying out a difference product operation to obtain a result of the base band DQPSK orthogonal component Z_k(ii) a Wherein phi is_kFor modulating the phase, θ, by a carrier_kIs the phase error.

Preferably, the dot product operation is:

DOT_k＝(i_k+q_k)·i_k-1+(i_k-q_k)·q_k-1；

the difference product operation is:

CROSS_k＝(i_k-q_k)·i_k-1-(i_k+q_k)·q_k-1。

preferably, the baseband DQPSK in-phase component W is divided into two parts_kAnd baseband DQPSK quadrature component Z_kPerforming a combined calculation to obtain an expression of phase error detection as

U_d＝DOT_K·(DOT_K-CROSS_K)·CROSS_K·(DOT_K+CROSS_K)；

Will the error U_dThe local carrier wave is input into a loop filter to correct the local carrier wave frequency and then input into a numerical control oscillator to recover the local carrier wave in real time.

Preferably, the in-phase demodulation in the I-path demodulation process is divided into:

X_k＝W_kW_k-1+Z_kZ_k-1＝cos(θ_k-θ_k-1)＝cos(Δθ_k)；

the quadrature demodulation in the Q-path demodulation process is:

Y_k＝Z_kW_k-1-W_kZ_k-1＝sin(θ_k-θ_k-1)＝sin(Δθ_k)。

preferably, the decision in the I-path demodulation processing and the decision in the Q-path demodulation processing correspond to:

the specific implementation of the carrier tracking device applicable to pi/4-DQPSK of the present invention is substantially the same as the embodiments of the carrier tracking method applicable to pi/4-DQPSK, and is not described herein again.

It should be understood that reference to "a plurality" herein means two or more. Other embodiments of the present application will be apparent to those skilled in the art from consideration of the specification and practice of the application disclosed herein. This application is intended to cover any variations, uses, or adaptations of the invention following, in general, the principles of the application and including such departures from the present disclosure as come within known or customary practice within the art to which the invention pertains. It is intended that the specification and examples be considered as exemplary only, with a true scope and spirit of the application being indicated by the following claims.

It should be noted that, in the present specification, the embodiments are described in a progressive manner, each embodiment focuses on differences from other embodiments, and the same and similar parts among the embodiments may be referred to each other. For the device embodiment, since it is basically similar to the method embodiment, the description is simple, and for the relevant points, refer to the partial description of the method embodiment.

The above disclosure is only for the purpose of illustrating the preferred embodiments of the present application and is not to be construed as limiting the scope of the present application, so that the present application is not limited thereto, and all equivalent variations and modifications can be made to the present application.