阅读说明：本技术 一种Ka频段宽带链路建模仿真系统 (Ka frequency band broadband link modeling simulation system ) 是由 王忠华 章仁飞 周武旸 任伟龙 于 2021-07-30 设计创作，主要内容包括：本发明公开了一种Ka频段宽带链路建模仿真系统,包括用户端、卫星端、地面端以及群时延及幅频特性模块。由发射端产生数据并经过发射端数传模块、Ka频段发射天线模块以及无线信道模块；然后到达卫星端,经过Ka频段卫星天线接收模块、多级变频相位噪声级联模块、Ka频段TWTA非线性模拟模块,经过卫星天线卫星发射模块发送到无线信道；最后到达接收端,经过天线接收模块以及接收端数传模块,将发射端数据和接收端数据输入到计算BER模块,计算出误码率和误帧率；而群时延及幅频特性模块贯穿整个链路,其中群时延由滤波器模块添加,幅频特性模块方便观察链路各处的幅频特性。本发明在链路各处使用多处元器件非线性模拟仿真,可以有效提高链路仿真的真实性。(The invention discloses a Ka frequency band broadband link modeling simulation system which comprises a user side, a satellite side, a ground side and a group delay and amplitude-frequency characteristic module. The transmitting terminal generates data and the data passes through the transmitting terminal data transmission module, the Ka frequency band transmitting antenna module and the wireless channel module; then, the signal reaches a satellite end and is sent to a wireless channel through a Ka frequency band satellite antenna receiving module, a multi-stage frequency conversion phase noise cascade module and a Ka frequency band TWTA nonlinear simulation module and a satellite antenna satellite transmitting module; finally, the data reaches a receiving end, the data of the transmitting end and the data of the receiving end are input into a BER calculating module through an antenna receiving module and a receiving end data transmission module, and the error rate and the frame error rate are calculated; the group delay and amplitude-frequency characteristic module penetrates through the whole link, wherein the group delay is added by the filter module, and the amplitude-frequency characteristic module is convenient for observing the amplitude-frequency characteristics of all parts of the link. The invention uses nonlinear analog simulation of a plurality of components at each position of the link, and can effectively improve the authenticity of the link simulation.)

1. A Ka frequency band broadband link modeling simulation system is characterized by comprising: a forward link ground end and a return link user end, a satellite end, a forward link user end and a return link ground end;

the forward link ground end and the return link user end comprise a sending end data transmission simulation module, a Ka frequency band antenna emission module and a Ka frequency band wireless link channel transmission module; the transmitting end data transmission simulation module is used for encoding, digitally modulating, forming and filtering original data and adding idle data; the Ka frequency band antenna transmitting module is used for outputting the modulated, molded and filtered signals to a wireless channel and simulating antenna gain; the Ka frequency band wireless link channel transmission module is used for receiving the signal transmitted by the Ka frequency band antenna transmission module;

the satellite terminal comprises a Ka frequency band satellite antenna receiving module, a multi-stage frequency conversion phase noise cascade module and a Ka frequency band TWTA nonlinear simulation module; the Ka frequency band satellite antenna receiving module is used for receiving transmission signals from a channel, amplifying the transmission signals according to antenna gain, amplifying weak signals through a low-noise amplifier and outputting the weak signals to the multistage frequency conversion phase noise cascade module; the multistage frequency conversion phase noise cascade module is used for adding the influence of phase noise into a frequency source model connected with a satellite payload mixer so that a frequency source oscillator directly outputs a waveform with the phase noise to carry out frequency mixing; the system comprises a Ka frequency band TWTA nonlinear simulation module, a TWTA nonlinear simulation module and a TWTA module, wherein the Ka frequency band TWTA nonlinear simulation module is generated according to simulation of an amplifier module in a SystemVue, and simulation parameters of the TWTA module are calculated according to input related parameters;

the forward link user side and the return link ground side comprise a receiving end data transmission simulation module and a Ka frequency band antenna receiving module; the receiving end data transmission simulation module is used for performing matched filtering, frame synchronization, down sampling, demodulation and decoding of received data and bit error rate statistics, and the Ka frequency band antenna receiving module is used for receiving transmission signals from a wireless channel and amplifying the transmission signals according to antenna gains; and then the weak signal is amplified and output by a low noise amplifier.

2. The Ka-band broadband link modeling simulation system according to claim 1, wherein: after the Ka frequency band wireless link channel transmission module receives the transmitted signal, the satellite-ground distance d and the carrier central frequency f are utilized_cCalculating the free space propagation loss PL:

PL(dB)＝92.44+20lgd(m)+20lgf_c(GHz)

and the input attenuation value is added to the calculation of the spatial propagation loss.

3. The Ka-band broadband link modeling simulation system according to claim 1, wherein: the Ka frequency band TWTA nonlinear simulation module carries out nonlinear modeling on the amplifier according to a Taylor series model, and carries out polynomial approximation on the nonlinear characteristic of the amplifier:

the subscript k represents the harmonic order, N represents the number of harmonic terms, even power terms do not contain the fundamental component of the signal, and only the nonlinear effect brought by odd power terms remains:

4. the Ka-band broadband link modeling simulation system according to claim 1, wherein: the Ka frequency band TWTA nonlinear simulation module carries out nonlinear modeling on the amplifier according to a double-parameter Saleh model, wherein the double-parameter Saleh model is as follows:

5. the Ka-band broadband link modeling simulation system according to claim 1, wherein: the Ka multi-access link modeling simulation system also comprises a group delay and amplitude-frequency characteristic module, wherein the group delay and amplitude-frequency characteristic module comprises a group delay module and an amplitude-frequency characteristic module; the group delay module is used for calculating the order of a preset filter by utilizing the central frequency, the pass band width, the pass band attenuation, the stop band width, the stop band attenuation and the sampling frequency of an input signal, and calculating the group delay of the filter, and the amplitude-frequency characteristic module is used for inserting an amplitude-frequency characteristic analyzer at any position of a link to analyze the amplitude-frequency characteristic of the position.

6. The Ka-band broadband link modeling simulation system according to claim 6, wherein: using a frequency translation relationship based on the parameters utilized by the group delay moduleConverting the technical index of the digital filter into the technical index of the analog filter to obtain a zero and a pole of the analog filter, and accordingly obtaining a system function of the corresponding analog filter, wherein if no repeated pole exists, the method comprises the following steps:

converting the system function from an analog domain s plane to a digital domain z plane by using a bilinear transformation method to obtain the system function of the digital filter:

after obtaining the system function of the digital filter, using z ═ e^jwConverting H (z) to H (e)^jw) And calculating group delay:

Technical Field

The invention relates to the technical field of satellite communication, in particular to a Ka frequency band broadband link modeling simulation system.

Background

In recent years, with the increase of a large number of networking devices and the difficulty of effective coverage of a ground wireless network in a part of regions, satellite communication can be used as an effective supplement to the ground network due to the characteristics of large satellite communication coverage area, capability of being combined with various multiple access technologies to form a communication network, wide communication frequency band, large capacity and the like. Therefore, the system simulation of the satellite communication under different coding modulation modes of each frequency band can verify and simulate the system communication capacity and the communication effectiveness before the satellite is transmitted.

In a satellite communication system, for a specific carrier frequency, different spreading, coding, modulation modes and the like have different signal-to-noise ratio requirements to achieve the communication error rate standard. Therefore, for different spreading, coding and modulation modes, the satellite physical layer modeling simulation is an urgent technical problem to be solved under the Ka frequency band single address condition. Therefore, a Ka frequency band broadband link modeling simulation system is provided.

Disclosure of Invention

The technical problem to be solved by the invention is as follows: a Ka frequency band broadband link modeling simulation system is provided for the problem of satellite physical layer modeling simulation of different spreading, coding and modulation modes under the condition of Ka frequency band single address. The system can simulate the physical layer of the satellite link under different spreading, coding and modulation modes, and verify the system capacity of the satellite communication system and the signal-to-noise ratio required by reaching a specific bit error rate through different coding and modulation modes.

The invention solves the technical problem by the following technical proposal, and the invention comprises a forward link ground end, a return link user end, a satellite end, a forward link user end and a return link ground end;

the forward link ground end and the return link user end comprise a sending end data transmission simulation module, a Ka frequency band antenna emission module and a Ka frequency band wireless link channel transmission module; the transmitting end data transmission simulation module is used for encoding, digitally modulating, forming and filtering original data and adding idle data; the Ka frequency band antenna transmitting module is used for outputting the modulated, molded and filtered signals to a wireless channel and simulating antenna gain; the Ka frequency band wireless link channel transmission module is used for receiving the signal transmitted by the Ka frequency band antenna transmission module;

the satellite terminal comprises a Ka frequency band satellite antenna receiving module, a multi-stage frequency conversion phase noise cascade module and a Ka frequency band TWTA nonlinear simulation module; the Ka frequency band satellite antenna receiving module is used for receiving transmission signals from a channel, amplifying the transmission signals according to antenna gain, amplifying weak signals through a low-noise amplifier and outputting the weak signals to the multistage frequency conversion phase noise cascade module; the multistage frequency conversion phase noise cascade module is used for adding the influence of phase noise into a frequency source model connected with a satellite payload mixer so that a frequency source oscillator directly outputs a waveform with the phase noise to carry out frequency mixing; the system comprises a Ka frequency band TWTA nonlinear simulation module, a TWTA module and a TWTA module, wherein the Ka frequency band TWTA nonlinear simulation module is used for simulation generation according to an amplifier module in a SystemVue, and simultaneously, simulation parameters of the TWTA module are calculated according to input related parameters;

the forward link user side and the return link ground side comprise a receiving end data transmission simulation module and a Ka frequency band antenna receiving module; the receiving end data transmission simulation module is used for performing matched filtering, frame synchronization, down sampling, demodulation and decoding of received data and bit error rate statistics, and the Ka frequency band antenna receiving module is used for receiving transmission signals from a wireless channel and amplifying the transmission signals according to antenna gains; and then the weak signal is amplified and output by a low noise amplifier.

Furthermore, after the Ka frequency band wireless link channel transmission module receives the transmitted signal, the satellite-ground distance d and the carrier central frequency f are utilized_cCalculating the free space propagation loss PL:

PL(dB)＝92.44+20lgd(m)+20lgf_c(GHz)

and the input attenuation value is added to the calculation of the spatial propagation loss.

Furthermore, the Ka-band TWTA nonlinear simulation module performs nonlinear modeling of the amplifier according to a Taylor series model, and performs polynomial approximation on the nonlinear characteristic of the amplifier:

the subscript k represents the harmonic order, N represents the number of harmonic terms, even power terms do not contain the fundamental component of the signal, and only the nonlinear effect brought by odd power terms remains:

furthermore, the Ka band TWTA nonlinear simulation module performs nonlinear modeling of the amplifier according to a two-parameter Saleh model, where the two-parameter Saleh model is:

furthermore, the Ka multiple access link modeling simulation system further comprises a group delay and amplitude-frequency characteristic module, wherein the group delay and amplitude-frequency characteristic module comprises a group delay module and an amplitude-frequency characteristic module; the group delay module is used for calculating the order of a preset filter by utilizing the central frequency, the pass band width, the pass band attenuation, the stop band width, the stop band attenuation and the sampling frequency of an input signal, and calculating the group delay of the filter, and the amplitude-frequency characteristic module is used for inserting an amplitude-frequency characteristic analyzer at any position of a link to analyze the amplitude-frequency characteristic of the position.

Further, a frequency translation relationship is employed based on the parameters utilized by the group delay moduleConverting the technical index of the digital filter into the technical index of the analog filter to obtain a zero and a pole of the analog filter, and accordingly obtaining a system function of the corresponding analog filter, wherein if no repeated pole exists, the method comprises the following steps:

converting the system function from an analog domain s plane to a digital domain z plane by using a bilinear transformation method to obtain the system function of the digital filter:

after obtaining the system function of the digital filter, using z ═ e^jwConverting H (z) to H (e)^jw) And calculating group delay:

compared with the prior art, the invention has the following advantages: according to the Ka frequency band broadband link modeling simulation system, a Ka frequency band TWTA nonlinear simulation module is adopted, phase noise is added into a multistage frequency conversion phase noise cascade module, a user-defined filter is arranged, and through the irrational component simulation module, the simulation system can obtain a more real simulation result and is worth being popularized and used.

Drawings

Fig. 1 is a flow chart of a data transmission simulation module at a sending end in the embodiment of the present invention;

FIG. 2 is a flow chart of a Ka-band satellite antenna receiving module according to an embodiment of the present invention;

FIG. 3 is a flow chart of a multi-stage frequency-conversion phase noise cascade module according to an embodiment of the present invention;

FIG. 4 is a flowchart of a Ka band TWTA nonlinear simulation module according to an embodiment of the present invention;

fig. 5 is a flowchart of an antenna receiving module of a user terminal and a ground station according to an embodiment of the present invention;

FIG. 6 is a flow chart of a receiving end data transmission simulation module according to an embodiment of the present invention;

fig. 7 is a flow chart (return) of the Ka band broadband link modeling simulation system in the embodiment of the present invention.

Detailed Description

The following examples are given for the detailed implementation and specific operation of the present invention, but the scope of the present invention is not limited to the following examples.

The embodiment provides a technical scheme: a Ka frequency band broadband link modeling simulation system comprises the following parts:

forward link ground side and reverse link user side:

the system comprises a transmitting end data transmission simulation module, a Ka frequency band wireless link channel transmission module and a Ka frequency band antenna transmitting module.

And the transmitting end data transmission simulation module is used for encoding, digitally modulating, forming and filtering the original data and adding idle data.

The Ka frequency band wireless link channel transmission module is used for receiving signals transmitted by an antenna and utilizing the satellite-ground distance d and the carrier central frequency f_cCalculating the free space propagation loss PL:

PL(dB)＝92.44+20lgd(m)+20lgf_c(GHz)

and adding the attenuation values of the input such as rain attenuation, ionospheric attenuation and the like into the calculation of the path loss (free space propagation loss).

The Ka frequency band antenna transmitting module is used for outputting the modulated, formed and filtered signals to a wireless channel, and an ideal amplifier is adopted to simulate the antenna gain, wherein the antenna gain is comprehensively provided according to the influence factors such as the transmitting power of the omnidirectional antenna, an antenna directional diagram and the like.

The modeling process needs to consider not only the modulation and coding mode but also parameters such as the frame length, wherein the data transmission simulation module and the satellite filter module are designed according to the requirements, and the Ka-band wireless link channel transmission module needs to consider factors such as rain attenuation and atmospheric dispersion

Satellite end:

the system comprises a Ka frequency band satellite antenna receiving module, a multi-stage frequency conversion phase noise cascade module and a Ka frequency band TWTA nonlinear simulation module.

The Ka frequency band satellite antenna receiving module is used for receiving transmission signals from a channel, amplifying the transmission signals according to antenna gain, amplifying weak signals through a low noise amplifier of the Ka frequency band satellite antenna receiving module, and outputting the weak signals to the multistage frequency conversion phase noise cascade module.

The multistage frequency conversion phase noise cascade module is used for adding the influence of phase noise into a frequency source model connected with a satellite effective load frequency mixer, so that a frequency source oscillator directly outputs a waveform with the phase noise to carry out frequency mixing.

In the Ka frequency range TWTA nonlinear simulation module, amplifier nonlinear simulation can be performed on the nonlinear characteristic of an amplifier according to a Taylor series model (power series model) by polynomial approximation:

the even power term does not contain the fundamental component of the signal, and because the satellite carrier frequency is far greater than the bandwidth of the transponder, only the intermodulation component falling in the band can be output when the intermodulation component passes through the filter. Therefore, only the odd power term left in the above equation brings nonlinear effects:

the nonlinear physical meaning of the power amplifier is described by using Taylor series, the subscript k indicates the harmonic order, and the number of harmonic terms N is increased, so that the number of the model can be effectively improved. However, the Taylor series model only describes the amplitude distortion characteristic of the power amplifier, and cannot reflect the phase distortion characteristic.

For non-linear modeling of TWTA, a two-parameter Saleh model can also be utilized:

wherein a is_r,β_rIs a fitting parameter for measuring AM/AM characteristics of the power amplifier, a_i,β_iIs a fitting parameter for measuring the AM/PM characteristic of the power amplifier.

The Saleh model not only has a simple form and can better approximate an original performance curve, but also can realize phase nonlinear modeling and is most widely used in TWTA. The improved Saleh model can also simulate Q, I two paths of quadrature bandpass:

wherein a is_r,β_rIs a fitting parameter for measuring AM/AM characteristics of the power amplifier, a_i,β_iIs a fitting parameter for measuring the AM/PM characteristic of the power amplifier.

And performing polynomial approximation on a given input-output curve of the amplifier by using MATLAB software based on a Taylor series model to obtain a linear fitting curve, namely the gain of the amplifier, and simultaneously obtaining important parameters such as a 1dB gain compression point, a third-order intermodulation point, a saturated power point compression value and the like, and inputting the parameters into a power amplifier module in a SystemVue for simulating a real amplifier.

The SystemVue amplifier module can also simulate AM-AM and AM-PM models, and the simulation is carried out by inputting relevant parameters, namely corresponding numerical values of an AM-AM curve and an AM-PM curve.

The addition of phase noise is considered in the modeling process, a TWTA module is generated according to corresponding model simulation, and simulation parameters of the TWTA module can be calculated according to input parameters such as a related saturation point.

Forward link user side and return link ground side:

the system comprises a receiving end data transmission simulation module and a Ka frequency band antenna receiving module. The receiving end simulation data transmission module not only comprises the inverse process of the transmitting end simulation data transmission module, but also comprises the calculation of the error rate, and finally the calculation result of the error rate can be output.

And the receiving end data transmission simulation module is used for performing matched filtering, frame synchronization, down sampling, demodulation and decoding on the received data and performing error rate statistics.

The Ka frequency band antenna receiving module is used for receiving transmission signals from a channel, amplifying the transmission signals according to antenna gain, amplifying weak signals through a low noise amplifier of the Ka frequency band antenna receiving module, and outputting the weak signals to the frequency conversion module.

Group delay and amplitude-frequency characteristic module

The preset order of the filter is obtained through theoretical calculation by utilizing the center frequency, the passband width (passband cut-off frequency), the passband attenuation, the stopband width (stopband cut-off frequency), the stopband attenuation and the sampling frequency of the input signal, so that the group delay characteristic of the filter can be calculated conveniently.

According to the above input parameters, adopting frequency conversion relationConverting the technical index of the digital filter into the technical index of the analog filter to obtain a zero and a pole of the analog filter, and accordingly obtaining a system function of the corresponding analog filter, wherein if no repeated pole exists, the method comprises the following steps:

wherein s is_pkFor the kth pole, A, of an analog filter_kFor the gain corresponding to the kth pole, H(s) is the Laplace domain function of the filter.

Converting the system function from an analog domain s plane to a digital domain z plane by using a bilinear transformation method to obtain the system function of the digital filter:

after obtaining the system function of the digital filter, using z ═ e^jwConverting H (z) to H (e)^jw) Calculating the group delay

For the amplitude-frequency characteristic module, the amplitude-frequency characteristic of the full link can be inserted at any position of the link by using a spectrum analyzer device (which can output an amplitude-frequency characteristic graph of a corresponding node) in the system mvue, and the amplitude-frequency characteristic of the full link is given by a spectrum analyzer at the radio frequency end (before decoding).

The working principle is as follows:

firstly, as shown in fig. 1, data subjected to systemvue is generated, coded and digitally modulated by MATLAB, subjected to operations such as framing, upsampling, shaping filtering and the like, inserted with idle data, subjected to carrier modulation and sent to a Ka band antenna transmitting module. And the Ka frequency band antenna transmitting module receives the signal modulated by the carrier, gives a certain antenna gain and sends the signal to a wireless channel. The Ka band satellite antenna receiving module receives a signal passing through a wireless channel, as shown in fig. 2, amplifies a transmission signal according to an antenna gain, amplifies a weak signal by a low noise amplifier of the Ka band satellite antenna receiving module, and outputs the weak signal to the multistage frequency conversion phase noise cascade module. As shown in fig. 3, the instability of the oscillator frequency is simulated by adding phase noise to the multi-stage frequency conversion phase noise cascade module. The signal is input to the Ka band TWTA nonlinear analog module through the multistage frequency conversion phase noise cascade module, the calculation method of the Ka band TWTA nonlinear analog module is described above, and the flow chart of the implementation is shown in fig. 4. The satellite antenna transmitting module (Ka band satellite antenna transmitting module) transmits signals from a satellite to a wireless channel, as shown in fig. 5, a user terminal or a ground station receives signals transmitted on the satellite, adds a certain antenna gain, transmits the signals to the receiving terminal data transmission simulation module as shown in fig. 6, outputs the received data through a series of inverse operations relative to the transmitting terminal data transmission simulation module, compares the received data with the data of the transmitting terminal, and calculates the BER.

To sum up, the Ka band broadband link modeling simulation system according to the above embodiment adopts the Ka band TWTA nonlinear simulation module, adds phase noise to the multistage variable frequency phase noise cascade module, and defines the filter setting, and through the irrational component simulation module, the simulation system can obtain a more real simulation result, and is worth being popularized and used.

Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention, and that variations, modifications, substitutions and alterations can be made to the above embodiments by those of ordinary skill in the art within the scope of the present invention.