CN105337677A - High-bandwidth large-scale MIMO channel simulation method and device - Google Patents

Abstract

The invention discloses a method and a device for simulating a large-scale MIMO channel with high bandwidth. The device is composed of a number of basic units for simulating two-input and two-output channels. The input signal that needs to be simulated can enter the channel fading simulator of this unit for channel simulation, and can also be cascaded and relayed to other units for simulation through the transmission channel; the simulated output signal can be converted into the simulated baseband through a digital-to-analog converter Analog signals can also be cascaded through the receiving channels to output intermediate results for the next unit to combine. In addition, the basic unit provides synchronization for the transmission of various data signals through the synchronization and timing modules, and realizes single-module and system-level data alignment. The simulation of building a massive MIMO channel can use the method of cascading and combining MxN two-input and two-output channel simulation basic units. The interconnection scheme is simple and flexible, easy to implement, and the internal logic and interface are unified, which is convenient for simulating a massive MIMO channel.

Description

A method and device for high-bandwidth massive MIMO channel simulation

technical field

The invention relates to the field of wireless communication and testing, in particular to a high-bandwidth large-scale multi-input multi-output channel simulation method, which is applied to the field of wireless communication system testing.

Background technique

Wireless channels are complex and changeable signal physical channels, and there are unfavorable factors such as multipath fading, flat fading, and noise that affect communication performance, and these are issues that must be considered in communication system research. Channel simulation is to ensure the same Under the communication protocol and system system, it is an essential test process for smooth communication between terminals developed by different manufacturers and system equipment provided by multiple manufacturers. The channel simulator can also be used to control and change channel parameters, and then understand the performance of communication equipment or communication means under different channel conditions. The MIMO wireless channel simulator can save the development cost of LTE-A mobile communication equipment, increase the flexibility of research and development, shorten the development cycle, reduce the overall development process and interconnection test time of base stations and terminal equipment, and reduce the cost of field testing. Time plays a very positive role in improving and ensuring the interconnection of different systems and terminal manufacturers.

The simulation of wireless channel characteristics can be divided into digital part simulation and analog part simulation. Digital baseband signal simulation is mainly composed of digital signal processing, which is a comprehensive application of high-speed signal processing technology and computer application technology. The simulation of the radio frequency part is mainly realized by the analog circuit, which completes the up-down conversion and amplification of the signal. The key component of the channel simulator is a digital multipath fading characteristic simulator with a discrete tapped delay line as the core. Its implementation consumes a lot of digital logic resources. The wider the analog signal bandwidth, the faster the digital signal acquisition speed and the higher the throughput rate. For the simulation of a multi-antenna channel with M transmitting antennas and N receiving antennas, the required digital multipath fading device increases with MxN times, and as the number of receiving antennas grows, the throughput rate of signal combination will also increase N times . Therefore, when the number of simulated logical sub-channels or the number of transceiver antennas increases, the signal processing capability and system throughput are faced with great challenges.

For MIMO channel simulation, a power divider is usually used to equally divide the signal that needs to be simulated, and then perform digital simulation through the fading simulator of each sub-channel after down-conversion and analog/digital conversion, and the output signal is then digital/analog converted and up-converted After that, the signals are combined by a power combiner. However, it is difficult to ensure the accuracy and consistency of the allocation and merging of the branches of the broadband analog signal, thus causing deviations in the simulation of each branch. In recent years, it has gradually developed into a method of splitting and combining digital signals at the baseband. However, as the signal bandwidth becomes wider and wider (bandwidth exceeding 100MHz), there are more and more MIMO input and output antennas (256 receiving/transmitting antennas), especially Massive Multi-Input-Multi-Output (Massive MIMO) technology In the application of 5G communication, the combination and transmission throughput of analog signals will be higher and higher, and the timing requirements of each channel will be higher and higher.

Contents of the invention

The purpose of the present invention is to provide a method and device for high-bandwidth large-scale MIMO channel simulation. This distributed pipeline processing scheme is based on low complexity, easy to implement, easy to expand the architecture, and can well adapt to future high-bandwidth large-scale Antenna applications.

In order to achieve the above object, the technical scheme adopted in the present invention is:

A high-bandwidth massive MIMO channel simulation device, including several analog two-input two-output channel basic units, a single analog two-input two-output channel basic unit includes a first analog-to-digital converter, a second analog-to-digital converter, a first Cascade input of transmitting channels, cascading input of the second transmitting channel, cascading input of the first receiving channel, cascading input of the second receiving channel, Gaussian white noise generator, external timing and synchronization module; the first analog-to-digital converter The output end of the cascaded input with the first transmission channel is connected to the first multiplexer, the output end of the first multiplexer is connected to the first multiplexer, and the first multiplexer is connected to the first sub-multiplexer respectively. The channel fading simulator, the second sub-channel fading simulator and the first transmission channel cascade output, the output terminals of the first sub-channel fading simulator and the second sub-channel fading simulator are respectively connected to the first adder and the second adder , the output end of the first adder is connected to the third adder, the output end of the second adder is connected to the fourth adder; the output end of the cascaded input of the second analog-to-digital converter and the second transmission channel is connected to the second multiple multiplexer, the output of the second multiplexer is connected to the second multiplexer, and the second multiplexer is respectively connected with the third sub-channel fading simulator, the fourth sub-channel fading simulator and the second Transmit channel cascade output, the output terminals of the third sub-channel fading simulator and the fourth sub-channel fading simulator are respectively connected to the first adder and the second adder; the first receive channel cascade input is connected to the third adder, the first The output terminals of the three adders are connected to the fifth adder, the fifth adder is connected to the third demultiplexer, and the third demultiplexer is respectively connected to the first digital-to-analog converter and the cascaded output of the first receiving channel; the second receiving channel The channel cascade input is connected to the fourth adder, the fourth adder is connected to the sixth adder, the sixth adder is connected to the fourth demultiplexer, and the fourth demultiplexer is respectively connected to the second digital-to-analog converter and the second receiver Channel cascade output; Gaussian white noise generators are respectively connected to the fifth adder and sixth adder; the first transmit channel cascade output and the second transmit channel cascade output are respectively connected to the next analog two-input two-output channel basic unit The cascading input of the first transmitting channel and the cascading input of the second transmitting channel; the cascading output of the first receiving channel and the cascading output of the second receiving channel are respectively connected to the cascading of the first receiving channel of the next analog two-input and two-output channel basic unit input and second receive channel cascaded input.

Several external timing and synchronization modules of the analog two-input and two-output channel basic unit are connected to the system clock and timing module.

A method for high-bandwidth massive MIMO channel simulation, comprising the steps of:

a) The analog two-input and two-output channel basic unit adopts two inputs and two outputs;

b) The input signal is the baseband data collected by the high-speed analog-to-digital converter after the broadband signal is down-converted, or the transmit antenna cascaded input data stream transmitted through the high-speed serial interface, and the multiplexer of digital logic is used to select one of them one;

c) The passed demultiplexer copies the first roadbed data stream three times, the first copy is transmitted to the first sub-channel fading simulator for simulation, and the second copy is transmitted to the second sub-channel fading simulator for simulation , the third copy is transmitted to the next module for simulation through the high-speed serial interface;

d) Use a digital logic demultiplexer to duplicate the second baseband data stream three times, the first copy is transmitted to the third sub-channel fading simulator for simulation, and the second copy is transmitted to the fourth sub-channel fading simulator for simulation Simulation, the third copy is transmitted to the next module for simulation through the high-speed serial interface;

e) using an external timing and synchronization module to synchronize the output of the first sub-channel fading simulator, the output of the third sub-channel fading simulator and the cascaded input data of the first receiving channel, and add them to obtain the first channel analog output signal, the same , synchronizing the output of the second sub-channel fading simulator, the output of the fourth sub-channel fading simulator and the cascaded input data of the second receiving channel, and adding them to obtain the second channel analog output signal;

f) The analog output signals of the two channels are superimposed with independent and uncorrelated Gaussian white noise;

g) Finally, the output signal of each channel simulates the baseband data through the digital-to-analog converter, and transmits it to the radio frequency module for up-conversion, or transmits it to the next-level receiving channel through the high-speed serial interface.

For the MIMO channel simulation of 2M input signals and 2N output signals, MxN analog two-input and two-output channel basic units are used for expansion. The expansion method is as follows:

(1) 2M road input signals are collected as baseband digital signals through the analog-to-digital converters in the basic unit of M analog two-input and two-output channels;

(2) The transmission channel cascade output of 2M input signals is respectively connected to the 2M transmission channel cascade inputs of the second-stage M analog two-input two-output channel basic unit, and the second-stage M analog two-input two-output channel basic unit The cascaded output of the transmitting channel of the unit is then connected to the third stage, and this sequence is expanded to N stages;

(3) There are M analog two-input and two-output channel basic units in each stage, and the receiving channel cascade output of the first analog two-input and two-output channel basic unit is connected to the receiving channel cascade input of the second unit, so Sequentially expand to the Mth analog two-input and two-output channel basic unit;

(4) at the two outputs of the Mth analog two-input-two-output channel basic unit, a Gaussian white noise source is superimposed on a total of N stages;

(5) Connect the 2N-stage analog digital signal to a digital-to-analog converter to generate 2N channel analog outputs.

The beneficial effects of the present invention are:

The method of the present invention combines the advantages of distributed signal processing, avoids the increase in computing capacity and transmission data volume caused by the increase of logical channels, solves the bottleneck of signal aggregation and transmission throughput in large-scale MIMO channel simulation, and is easy expand. Specifically:

1) The basic two-input and two-output module unit can realize two-dimensional expansion in the direction of receiving channel or transmitting channel, and it is easy to realize the simulation of massive MIMO channel.

2) Standard input and output interfaces, the same computing architecture and capacity, fixed resource consumption.

3) The signal splitter and combiner are implemented digitally to ensure the consistency of each sub-channel. When multiple signals are split and merged, due to the delay introduced in data transmission and cooperative control, an external synchronization module based on flow control is used to achieve data alignment.

4) The throughput rate of the interface between each basic module depends on the combined throughput rate of the two channels, and will not increase with the increase of the number of analog channels.

Description of drawings

Fig. 1 is the basic unit based on two-input two-output channel simulation of the present invention;

In the figure, IN ₁ /IN ₂ : baseband input signal after channel 1/2 analog-to-digital conversion;

IN ₁ '/IN ₂ ': cascade input signal of channel 1/2 baseband transmit antenna;

X ₁ /X ₂ : baseband analog signal of channel 1/2;

H _1,1 /H _2,1 /H _1,2 /H _2,2 : sub-channel multipath fading simulator;

S ₁ /S ₂ : the cascaded input signal of the channel 1/2 baseband receiving antenna;

N ₁ /N ₂ : channel 1/2 Gaussian white noise signal output;

OUT ₁ /OUT ₂ : Baseband analog output signal before channel 1/2 digital-to-analog conversion;

OUT ₁ '/OUT ₂ ': cascaded output signal of channel 1/2 baseband receiving antenna;

Fig. 2 is the basic unit-based MIMO 4x4 channel simulation extension method of the present invention.

detailed description

The present invention will be further described below in conjunction with specific drawings.

As shown in Figure 1, a device for simulating a high-bandwidth massive MIMO channel of the present invention includes several analog two-input and two-output channel basic units, and a single analog two-input and two-output channel basic unit includes a first analog-to-digital converter 1 , the second analog-to-digital converter 3, the first transmit channel cascade input 2, the second transmit channel cascade input 4, the first receive channel cascade input 5, the second receive channel cascade input 6, Gaussian white noise generator 7. External timing and synchronization module 8; the output of the first analog-to-digital converter 1 and the cascaded input 2 of the first transmission channel is connected to the first multiplexer 9, and the output of the first multiplexer 9 The terminal is connected to the first demultiplexer 10, and the first demultiplexer 10 is respectively connected with the first sub-channel fading simulator H _1,1 , the second sub-channel fading simulator H _2,1 and the cascaded first transmission channel Output 11, the output terminals of the first sub-channel fading simulator H _1,1 and the second sub-channel fading simulator H _2,1 are respectively connected to the first adder 12 and the second adder 13, the output of the first adder 12 The third adder 14 is terminated, and the output of the second adder 12 is connected to the fourth adder 15; the output of the second analog-to-digital converter 3 and the second transmission channel cascade input 4 is connected to the second multiplexer 16, the output end of the second multiplexer 16 is connected to the second demultiplexer 17, and the second demultiplexer 17 is respectively connected with the third sub-channel fading simulator H _1,2 , the fourth sub-channel Fading simulator H _2,2 and the second transmission channel cascade output 18, the output terminals of the third sub-channel fading simulator H _1,2 and the fourth sub-channel fading simulator H _2,2 are respectively connected to the first adder 12 And the second adder 13; the first receiving channel cascade input 5 is connected to the third adder 14, the output of the third adder 14 is connected to the fifth adder 19, and the fifth adder 19 is connected to the third demultiplexer 20 , the third demultiplexer 20 is respectively connected to the first digital-to-analog converter 21 and the first receiving channel cascaded output 22; the second receiving channel cascaded input 6 is connected to the fourth adder 15, and the fourth adder 15 is connected to the sixth Adder 23, the sixth adder 23 is connected to the fourth demultiplexer 24, and the fourth demultiplexer 24 is respectively connected to the second digital-to-analog converter 25 and the second receiving channel cascade output 26; Gaussian white noise generator 7 Connect the fifth adder 19 and the sixth adder 23 respectively; the first transmit channel cascade output 11 and the second transmit channel cascade output 18 are respectively connected to the first transmit channel cascade of the next analog two-input two-output channel basic unit Input and the second transmission channel cascading input; the first receiving channel cascading output 22 and the second receiving channel cascading output 26 are respectively connected to the first receiving channel cascading input 5 and the second analog two-input two-output channel basic unit Two receive channel cascade input 6.

The external timing and synchronization modules 8 of several analog two-input and two-output channel basic units are all connected to the system clock and timing module 27 .

Through the first analog-to-digital converter and the second analog-to-digital converter (ADC1/2), the baseband input complex signals IN ₁ and IN ₂ of channels 1 and 2 are collected to obtain the transmitted signal data that needs to be simulated.

The analog-to-digital converter input IN ₁ /IN ₂ is cascaded with the transmission channel. The input signal IN ₁ '/IN ₂ ' is selected by the first multiplexer and the second multiplexer and output as data streams X ₁ and X ₂ . The input signal of the multiplexer is selected as the input of the analog-to-digital converter.

The inputs X ₁ and X ₂ of the first multiplexer and the second multiplexer are duplicated into three identical data streams X ₁ and X ₂ by the demultiplexer. The same two data streams respectively enter the digital multipath fading simulator corresponding to the sub-channel for channel multipath fading simulation, and the output signal streams are H _1,1 X ₁ , H _2,1 X ₁ , H _1,2 X ₂ and H _2,2 X ₂ . The third data stream of X ₁ and X ₂ is transmitted to the next-level transmission channel through a high-speed serial interface or an optical fiber interface, and is cascaded as a transmission channel to output 1 and 2.

Through the external timing and synchronization module, the H 1, ₁ X ₁ and H _{1, 2} X ₂ data streams are aligned, and the first adder is used to combine them into the first output signal. Similarly, H ₂ , 1 X ₁ and H are aligned _2,2 X ₂ data streams and use the second adder to combine into the second output signal. The first output signal and the second output signal are respectively added to the cascade input of the first receiving channel and the cascading input of the second receiving channel through the third adder and the fourth adder to obtain Z ₁ and Z ₂ , and the result for:

Z ₁ =H _1,1 X ₁ +H _1,2 X ₂ +S ₁

Z ₂ ＝H _2,1 X ₁ +H _2,2 X ₂ +S ₂

Finally, the Z ₁ and Z ₂ data streams are superimposed with white noise N ₁ and N ₂ through a Gaussian white noise generator to generate output signals Y ₁ and Y ₂ . , whose expression is:

Y ₁ ＝H _1,1 X ₁ +H _1,2 X ₂ +S ₁ +N ₁

Y ₂ ＝H _2,1 X ₁ +H _2,2 X ₂ +S ₂ +N ₂

After outputting the analog signal Y ₁ and Y ₂ , two outputs are generated through the third demultiplexer and the fourth demultiplexer, one of which is transmitted to the first digital-to-analog converter and the second digital-to-analog converter, and the simulated post-analog The digital signal is converted into a baseband analog signal, and the other output data stream is transmitted to the next receiving channel through a high-speed serial interface or an optical fiber interface, as the cascaded output of the first receiving channel and the cascading output of the second receiving channel.

For the analog two-input two-output channel basic unit, the digital-to-analog and analog-to-digital converter interfaces are used to transmit multi-channel physical signals, and the cascaded input/output signal interface is used to transmit cascaded analog input signals or intermediate output signals after analog , can be connected by high-speed serial signal or optical fiber.

By cascading N analog two-input two-output channel basic unit transmit channel cascade output and input, it can be expanded to 2N analog channel output, and can also be cascaded by cascading M analog two-input two output channel basic unit receive channel cascade Output and input, expanded to 2M analog channel inputs. In this way, massive MIMO channel simulation with 2Mx2N sub-channels is realized.

Below in conjunction with accompanying drawing 2, M=2 in the scheme of the present invention, N=2 carries out cascading expansion, and the method for simulating four-input four-output channels is described in more detail, and concrete steps are as follows:

1) Using four identical analog two-input and two-output channel basic units M1-M4, configure the corresponding sub-channel fading simulation parameters H _1,1 , H _2,1 ... H _4,4 as shown in Figure 2 for each unit.

2) Collect four baseband input complex signals IN ₁ -IN ₄ with analog channels through two analog-to-digital converters in M1 and M4 respectively, to obtain the transmitted signal data that needs to be simulated.

3) The input signal of the multiplexer in M1 and M4 is selected as the input of the analog-to-digital converter.

4) The demultiplexer in M1 and M4 copies each input into three identical data streams IN1-IN4, two of which enter the corresponding sub-channel simulators for simulation, and the third data stream passes through the high-speed serial Line interface or optical fiber interface to transmit channel cascade input of M2 and M3 basic units.

5) The input signal of the multiplexer in M2 and M3 is selected as the cascaded input, and replicated three ways through the demultiplexer.

6) Through the external timing and synchronization module, the sub-channel simulation with X ₁ and X ₂ as input is realized in M1 and M2, the data stream is aligned and merged, and the sub-channel with X ₃ and X ₄ as input is realized in M3 and M4 Channel simulation, alignment of data streams and merging.

7) Through the external timing and synchronization module, using the automatic delay alignment mechanism based on flow control, the combined signals in M1 and M2 are cascaded through the receiving channel and output to the receiving channel cascading input of M3 and M4.

8) Through the adders and synchronization logic in M3 and M4, the combination of the sub _- channel simulated data stream with X1 and X2 as input and the sub _- channel simulated data stream with _X3 and _X4 as input is realized.

9) The last four output data streams are superimposed with white noise N ₁ -N ₄ by Gaussian white noise generators in M3 and M4 to generate output signals Y ₁ and Y ₂ . , whose expression is:

Y ₁ ＝H _1,1 X ₁ +H _1,2 X ₂ +H _1,3 X ₃ +H _1,4 X ₄ +N ₁

Y ₂ ＝H _2,1 X ₁ +H _2,2 X ₂ +H _2,3 X ₃ +H _2,4 X ₄ +N ₂

Y ₃ ＝H _3,1 X ₁ +H _3,2 X ₂ +H _3,3 X ₃ +H _3,4 X ₄ +N ₃

Y ₄ ＝H _4,1 X ₁ +H _4,2 X ₂ +H _4,3 X ₃ +H _4,4 X ₄ +N ₄

10) Output the analog signals Y ₁ -Y ₄ through the demultiplexer to select and output to the digital-to-analog converter, and convert the analog digital signals into baseband analog signals OUT1-OUT4.

11) For MIMO channel simulation with 2M input and 2N output, connect the transmit channel cascade output and transmit channel cascade input of the N-level analog two-input two-output channel basic unit, and cascade the M-level analog two-input two-output channel basic unit receiving Channel cascading output and receiving channel cascading input can realize massive MIMO channel simulation with 2Mx2N sub-channels.

Considering factors such as physical device performance and capacity, the basic unit of this expansion method adopts two inputs and two outputs, but is not limited thereto. With the improvement of equipment performance, speed and capacity, any 2Mx2N channel simulation module can be implemented as a basic unit, thereby reducing the demand for the number of basic units in large-scale channel simulation.

The above is only a preferred embodiment of the present invention, it should be pointed out that for those of ordinary skill in the art, without departing from the principle of the present invention, some improvements and modifications can also be made, and these improvements and modifications are also possible. It should be regarded as the protection scope of the present invention.

Claims (4)

1. A device for high-bandwidth massive MIMO channel simulation, characterized in that: it comprises several analog two-input and two-output channel basic units, and a single analog two-input and two-output channel basic unit comprises a first analog-to-digital converter, a second analog digital converter, cascade input of the first transmit channel, cascade input of the second transmit channel, cascade input of the first receive channel, cascade input of the second receive channel, Gaussian white noise generator, external timing and synchronization module; The output end of the cascade input of the first analog-to-digital converter and the first transmission channel is connected to the first multiplexer, and the output end of the first multiplexer is connected to the first multiplexer, and the first multiplexer The first sub-channel fading simulator, the second sub-channel fading simulator and the cascaded output of the first transmission channel are respectively connected, and the output terminals of the first sub-channel fading simulator and the second sub-channel fading simulator are respectively connected to the first addition device and a second adder, the output of the first adder is connected to the third adder, and the output of the second adder is connected to the fourth adder; the second analog-to-digital converter and the second transmission channel cascade input The output end is connected to the second multiplexer, the output end of the second multiplexer is connected to the second multiplexer, and the second multiplexer is respectively connected to the third sub-channel fading simulator, the fourth sub-channel The cascade output of the fading simulator and the second transmission channel, the output terminals of the third sub-channel fading simulator and the fourth sub-channel fading simulator are respectively connected to the first adder and the second adder; the cascade input of the first receiving channel is connected to The third adder, the output end of the third adder is connected to the fifth adder, the fifth adder is connected to the third demultiplexer, and the third demultiplexer is respectively connected to the first digital-to-analog converter and the first receiving channel stage cascade output; the cascade input of the second receiving channel is connected to the fourth adder, the fourth adder is connected to the sixth adder, the sixth adder is connected to the fourth demultiplexer, and the fourth demultiplexer is respectively connected to the second digital-analog The cascaded output of the converter and the second receiving channel; the Gaussian white noise generator is respectively connected to the fifth adder and the sixth adder; the cascaded output of the first transmitting channel and the cascading output of the second transmitting channel are respectively connected to the next analog two inputs The first transmit channel cascade input and the second transmit channel cascade input of the two-output channel basic unit; the first receive channel cascade output and the second receive channel cascade output are respectively connected to the next analog two-input and two-output channel basic unit The first receive channel cascade input and the second receive channel cascade input. 2. The device for high-bandwidth massive MIMO channel simulation as claimed in claim 1, characterized in that: several external timing and synchronization modules for simulating two-input and two-output channel basic units are all connected to system clock and timing module. 3. A method for high-bandwidth massive MIMO channel simulation, characterized in that: comprise the steps: a) The analog two-input and two-output channel basic unit adopts two inputs and two outputs; b) The input signal is the baseband data collected by the high-speed analog-to-digital converter after the broadband signal is down-converted, or the transmit antenna cascaded input data stream transmitted through the high-speed serial interface, and the multiplexer of digital logic is used to select one of them one; c) The passed demultiplexer copies the first roadbed data stream three times, the first copy is transmitted to the first sub-channel fading simulator for simulation, and the second copy is transmitted to the second sub-channel fading simulator for simulation , the third copy is transmitted to the next module for simulation through the high-speed serial interface; d) Use a digital logic demultiplexer to duplicate the second baseband data stream three times, the first copy is transmitted to the third sub-channel fading simulator for simulation, and the second copy is transmitted to the fourth sub-channel fading simulator for simulation Simulation, the third copy is transmitted to the next module for simulation through the high-speed serial interface; e) using an external timing and synchronization module to synchronize the output of the first sub-channel fading simulator, the output of the third sub-channel fading simulator and the cascaded input data of the first receiving channel, and add them to obtain the first channel analog output signal, the same , synchronizing the output of the second sub-channel fading simulator, the output of the fourth sub-channel fading simulator and the cascaded input data of the second receiving channel, and adding them to obtain the second channel analog output signal; f) The analog output signals of the two channels are superimposed with independent and uncorrelated Gaussian white noise; g) Finally, the output signal of each channel simulates the baseband data through the digital-to-analog converter, and transmits it to the radio frequency module for up-conversion, or transmits it to the next-level receiving channel through the high-speed serial interface. 4. the method for high-bandwidth massive MIMO channel simulation as claimed in claim 3, is characterized in that: For the MIMO channel simulation of 2M input signals and 2N output signals, MxN analog two-input and two-output channel basic units are used for expansion. The expansion method is as follows: (1) 2M road input signals are collected as baseband digital signals through the analog-to-digital converters in the basic unit of M analog two-input and two-output channels; (2) The transmission channel cascade output of 2M input signals is respectively connected to the 2M transmission channel cascade inputs of the second-stage M analog two-input two-output channel basic unit, and the second-stage M analog two-input two-output channel basic unit The cascaded output of the transmitting channel of the unit is then connected to the third stage, and this sequence is expanded to N stages; (3) There are M analog two-input and two-output channel basic units in each stage, and the receiving channel cascade output of the first analog two-input and two-output channel basic unit is connected to the receiving channel cascade input of the second unit, so Sequentially expand to the Mth analog two-input and two-output channel basic unit; (4) at the two outputs of the Mth analog two-input-two-output channel basic unit, a Gaussian white noise source is superimposed on a total of N stages; (5) Connect the 2N-stage analog digital signal to a digital-to-analog converter to generate 2N channel analog outputs.