A method for simulating secondary radar and DME signals based on USRP

Abstract

The application discloses a secondary radar and DME signal simulation method based on USRP, and the method comprises the following steps: generating binary original data before sampling modulation of corresponding message types according to inquiry, response or broadcast message types; modulating the binary original data by using corresponding modulation modes to generate I / Q modulation data; sampling the I / Q modulation data according to a sampling rate parameter to generate I / Q sampling data; and outputting the I / Q sampling data after superimposing interference signals to a radio frequency end for conversion output. The application is based on software defined radio technology, signal data generation, sampling data generation, noise superposition and I / Q modulation sampling data generation are realized by software, the hardware development difficulty of different modulation modes and different signal simulation is reduced, the combination of different signals, different modulation modes and different noise interference superposition can be realized, and the generation simulation of complex signals under different links is realized.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of radar signal processing, and particularly relates to a secondary radar and DME signal simulation method based on a USRP (Universal Software Radio Peripheral). BACKGROUND

[0002] The basic idea of software radio is to place the wideband analog-to-digital converter (A / D) and digital-to-analog converter (D / A) as close to the radio frequency antenna as possible. On this hardware platform, various functional modules of the radio are implemented by software technology. By software programming, various communication frequency bands such as HF, VHF, UHF and SHF can be selected; by software programming, sampling, quantization, encoding / decoding, operation processing and transformation of transmitted information can be completed to realize the functions of the radio frequency radio; by software programming, different channel modulation modes such as amplitude modulation, frequency modulation, single sideband, data, frequency hopping and spread spectrum can be selected; by software programming, different security structures, network protocols and control terminal functions can be realized. Software radio technology is a software-based, computationally intensive operation.

[0003] Software-defined radio (SDR) is a new type of radio architecture and a new solution in the radio neighborhood. Its characteristic is to reconfigure the same hardware through dynamic and variable software programming, and to complete different functions through the combination and adjustment of the software and hardware layers. Software radio technology migrates as many functions as possible from the previous hardware implementation to the software layer for reconfigurable, upgradeable structured software implementation, so that the software radio solution has strong openness, scalability, modularity, ease of debugging and reconfigurability.

[0004] The prior art has the following disadvantages:

[0005] 1. The radio signal simulation developed by relying on hardware has high development cost, great development difficulty, long development cycle, difficult problem positioning, and single function and poor expandability.

[0006] 2. The signal simulation realized by the existing software radio solution is single, the modulation frequency band is relatively fixed, and the software degree is not high.

[0007] 3. The radio signal simulation in the existing air navigation monitoring neighborhood has low integration, single simulation signal type, strong coupling dependence on hardware, and weak expandability. SUMMARY

[0008] In order to overcome the problems of great development difficulty, long cycle, difficult problem positioning and difficult function expansion existing in the prior art radio signal simulation technology relying on hardware implementation, the application provides a secondary radar and DME signal simulation method based on USRP. The application is based on software defined radio technology, and signal data generation, sample data generation, noise superposition and I / Q modulation sample data generation are realized through software, so that the hardware development difficulty of different modulation modes and different signal simulation is reduced, combination of different signals, different modulation modes and different noise interference superposition can be realized, and generation and simulation of complex signals in various environments are realized.

[0009] The application is realized through the following technical scheme:

[0010] The secondary radar and DME signal simulation method based on USRP comprises the following steps:

[0011] According to the inquiry, response or broadcast message type, binary original data before sample modulation of the corresponding message type is generated;

[0012] The binary original data is modulated by using a corresponding modulation mode to generate I / Q modulation data;

[0013] The I / Q modulation data is sampled according to a sampling rate parameter to generate I / Q sample data;

[0014] The I / Q sample data is superimposed with interference signals and then output to a radio frequency end for conversion and output.

[0015] As a preferred embodiment, the inquiry, response or broadcast information type of the application is dynamically controlled in the form of external input parameters, and at least one kind of data in (1)-(7) can be generated:

[0016] (1) pulse waveform data of a western system IFF inquiry without sampling with parameters;

[0017] (2) pulse waveform data of a western system IFF response without sampling with parameters;

[0018] (3) pulse waveform data of an S mode inquiry without sampling with parameters;

[0019] (4) pulse waveform data of an S mode response without sampling with parameters;

[0020] (5) pulse waveform data of an ADS-B broadcast without sampling with parameters;

[0021] (6) pulse waveform data of a DME inquiry without sampling with parameters;

[0022] (7) pulse waveform data of a DME response without sampling with parameters.

[0023] As a preferred embodiment, the external input parameters of the present application are used to calculate the value of each bit of the message packet, each bit can be mapped to 1us or 0.5us pulse width or other preset pulse width, and the specific mapping rule is determined by different signal formats.

[0024] As a preferred embodiment, the modulation mode of the present application at least includes one of (1)-(3):

[0025] (1) ASK modulation;

[0026] (2) DPSK modulation;

[0027] (3) AM modulation.

[0028] As a preferred embodiment, the interference signal superimposed by the present application at least includes one of (1)-(4):

[0029] (1) white noise interference;

[0030] (2) multipath noise interference;

[0031] (3) single pulse interference;

[0032] (4) co-frequency interference.

[0033] In a second aspect, the present application provides a USRP-based radio signal simulation device, comprising:

[0034] a data generation module, which generates binary original data before sampling modulation corresponding to the message type according to the inquiry, response or broadcast information type;

[0035] a modulation module, which modulates the binary original data to generate I / Q modulation data by using the corresponding modulation mode;

[0036] a data sampling module, which samples the I / Q modulation data to generate I / Q sampling data according to the sampling rate parameter;

[0037] an interference superimposition module, which superimposes interference signals on the I / Q sampling data and then outputs to the radio frequency end for conversion output.

[0038] As a preferred embodiment, the data generation module of the present application includes seven typical signal generation modules, such as MARK X / XII western system IFF inquiry data generation unit, MARK X / XII western system IFF response data generation unit, S-mode inquiry data generation unit, S-mode response data generation unit, ADS-B broadcast data generation unit, DME inquiry data generation unit, and DME response data generation unit.

[0039] As a preferred embodiment, the modulation module of the present application comprises an ASK modulation unit, a DPSK modulation unit and an AM modulation unit.

[0040] As a preferred embodiment, the interference superposition module of the present application comprises a white noise interference unit, a multipath interference unit, a co-channel interference unit and a single-pulse interference unit.

[0041] In a third aspect, the present application provides a USRP-based radio signal simulation system, comprising the above-mentioned USRP-based radio signal simulation device and a hardware device.

[0042] The hardware device comprises a master control unit, a DA conversion unit, a cache unit and a radio frequency channel management unit.

[0043] The radio signal simulation device transmits the data after sampling and superimposing the interference signal to the cache unit for caching, the master control unit controls the DA conversion unit to perform DA conversion on the data cached in the cache unit, and the DA-converted data is output by the radio frequency channel management unit.

[0044] The present application has the following advantages and beneficial effects:

[0045] 1. The present application provides an open, standardized and modular general-purpose software radio signal simulation technology, which is based on a software control and redefinition platform, and different functions can be realized by selecting different software modules, and the software can be upgraded and updated, and only the simplest function support needs to be maintained at the hardware level. The present application realizes the main functions (signal generation, modulation, sampling, interference superposition, etc.) in signal simulation by software, and the hardware is only responsible for realizing digital-to-analog conversion, setting the carrier frequency and carrier power, i.e. the hardware only needs to bear the subsequent radio frequency function. Therefore, if a new service or modulation mode is to be realized, only a new software module needs to be added to realize the new service or modulation mode, overcoming the defects and problems existing in the existing hardware-based radio simulation.

[0046] 2. The core module of the signal data generation of the present application is completed in software, which has high running efficiency, and the signal simulation capability can be further improved by improving the PC-level performance, and the signal simulation, noise interference, modulation mode and function optimization capabilities of the software module can be further expanded and upgraded without changing the FPGA hardware.

[0047] 3. The present application realizes signal simulation based on modular software radio, which greatly improves the development efficiency, reduces the hardware dependency, shortens the project development cycle, and has good code and module reuse capability, and has a series of advantages such as universal structure, software function, good interoperability, etc.

[0048] 4. The application provides data support and technical support for the construction of a multi-signal, multi-band and signal multi-noise interference air traffic control monitoring multi-functional wireless communication. BRIEF DESCRIPTION OF DRAWINGS

[0049] The drawings described herein are used to provide further understanding of the embodiments of the application, form a part of the application, and do not constitute a limitation of the embodiments of the application. In the drawings:

[0050] Figure 1 The method flowchart of the embodiments of the application.

[0051] Figure 2 The computer principle block diagram of the embodiments of the application.

[0052] Figure 3 The device principle block diagram of the embodiments of the application.

[0053] Figure 4 The system principle block diagram of the embodiments of the application. DETAILED DESCRIPTION

[0054] In order to make the purpose, technical scheme and advantages of the application more clear and obvious, the application is further described in detail below in combination with embodiments and drawings, the illustrative embodiments of the application and the description thereof are used to explain the application, and do not constitute a limitation of the application.

[0055] Embodiment 1

[0056] In view of the technical problems existing in the existing radio signal simulation technology, such as the difficulty, long cycle and single function of the radio signal simulation development relying on hardware implementation; the single signal simulation and relatively fixed modulation frequency band of the existing software radio implementation. The embodiments of the application propose a secondary radar and DME signal simulation method based on USRP, as shown in Figure 1 The method of the embodiments of the application includes the following steps:

[0057] Step one, according to the inquiry, response or broadcast message type, generate the binary original data before sampling modulation corresponding to the message type.

[0058] Step two, select the modulation mode, modulate the binary original data to generate I / Q modulation data;

[0059] Step three, according to the sampling rate parameter, sample the I / Q modulation data to generate I / Q sampling data;

[0060] Step four, after the I / Q sampling data is superimposed with interference signals, it is output to the radio frequency end for conversion output.

[0061] Further, in step one of the embodiment of the present application, the inquiry, response or broadcast information type is dynamically controlled in the form of external input parameters, and binary original data of various types of signals can be generated, including but not limited to IFF inquiry data generation of MARK X / XII western system, IFF response data generation of MARK X / XII western system, S-mode inquiry data generation, S-mode response data generation, ADS-B broadcast data generation, DME inquiry data generation, DME response data generation and the like. The IFF inquiry data generation of MARK X / XII western system specifically generates PPM pulse waveform data of the western system IFF inquiry without sampling the inquiry parameters; the IFF response data generation of MARK X / XII western system specifically generates PPM pulse waveform data of the western system IFF response without sampling the inquiry parameters; the S-mode inquiry data generation specifically generates PPM pulse waveform data of the S-mode inquiry without sampling the parameters; the S-mode response data generation specifically generates PPM pulse waveform data of the S-mode response without sampling the inquiry parameters; the ADS-B broadcast data generation specifically generates PPM pulse waveform data of the ADS-B broadcast without sampling the parameters; the DME inquiry data generation specifically generates pulse waveform data of the DME inquiry without sampling the parameters; and the DME response data generation specifically generates pulse waveform data of the DME response without sampling the parameters.

[0062] In addition, the external input parameters are applicable to calculating the value of each bit of the message, for example, the S-mode DF21 response signal contains an 8-microsecond leading pulse and a 112-microsecond data field, and 0.5 microsecond is taken as a step, so that 1 bit represents 0.5 microsecond and 2 bits represent 1 microsecond of DF21 data, and the original message data of 240 bits of DF21 message are calculated according to the value of the external input variable and the S-mode response signal format. The other six types of signals adopt similar ways, which will not be described here. Specifically, the DME inquiry response data should satisfy the Gaussian distribution, and the adaptive adjustment ability of the DME pulse width under different hardware radio frequency parameters needs to be considered in the specific implementation process.

[0063] Further, step two of the embodiment of the present application can realize various modulation modes, including but not limited to ASK modulation, DPSK modulation and AM modulation.

[0064] Wherein, the ASK modulation type adopts 2ASK modulation, 2ASK modulation is binary amplitude shift keying, also called OOK modulation, and the generation mode of the 2ASK modulation signal usually has two kinds: analog modulation method (multiplier method) and keying method. The embodiment adopts the analog modulation method, that is, the multiplier is used to realize. The embodiment of the application modulates the unsampled pulse waveform data into the ASK modulation I / Q zero intermediate frequency data before sampling through ASK modulation.

[0065] DPSK modulation refers to using the change of the relative phase of the carrier between the symbols before and after the modulation signal to transmit information. The DPSK modulation signal adopted in the embodiment should satisfy b1=a1, Principle. The embodiment of the application modulates the unsampled pulse waveform data into the DPSK modulation I / Q zero intermediate frequency data before sampling through DPSK modulation.

[0066] AM modulation, that is, amplitude modulation, the generation of the AM amplitude modulation signal can add the modulation signal to the direct current, and then multiply it with the carrier signal, that is, the general amplitude modulation can be realized. The embodiment can adopt the low-level amplitude modulation method and the high-level amplitude modulation method. The embodiment of the application modulates the unsampled pulse waveform data into the AM modulation I / Q zero intermediate frequency data before sampling through AM modulation.

[0067] Further, step three of the embodiment of the application samples the I / Q modulation data to generate 1 second I / Q sampling data. Wherein, the sampling rate and the signal frequency are dynamically controlled in the form of parameters. For example, the embodiment sets the transmission signal repetition frequency to 1000Hz, and the signal sampling rate to 20MHz, so that after sampling, a set of I / Q data is obtained, the data amount is 2e7, and the sampling points appear once every 2e4 transmission signals. The other repetition frequencies and sampling rates are not enumerated here.

[0068] Further, step four of the embodiment of the application adopts a plurality of interference superposition modes to realize the I / Q sampling data with increased corresponding interference, including but not limited to white noise interference, multipath interference, co-frequency interference, and single pulse interference.

[0069] White noise interference with a relative interference amplitude is superimposed on the I / Q sampling data, so as to simulate the signal transmission of the signal in a high noise environment. Wherein, the relative interference amplitude is controlled in the form of parameters.

[0070] Multipath noise interference with a certain relative amplitude and interference delay time is superimposed on the I / Q sampling data, so as to simulate the mixed signal obtained after the signal is propagated through different propagation paths, that is, the same signal appears after a certain time delay of the signal. Wherein, the relative amplitude of the multipath interference and the interference delay time are controlled in the form of parameters.

[0071] A single-pulse interference with a fixed frequency, fixed pulse width, and relative interference amplitude is superimposed on the I / Q sampled data to simulate the mixed signal obtained after the signal has been subjected to single-pulse interference. The relative interference amplitude, single-pulse repetition frequency, and pulse width are controlled as parameters.

[0072] The I / Q sampled data are superimposed with other signals of the same frequency that interfere with the modulation signal at certain time intervals and with relative amplitudes, thereby simulating the mixed signal after interference from other signals in the same frequency band during signal transmission. The type of interference signal, the relative amplitude of the interference, and the interference delay time are controlled as parameters.

[0073] This embodiment also proposes a computer device for performing the methods described above in this embodiment.

[0074] Specifically, such as Figure 2 As shown, a computer device includes a processor, internal memory, and a system bus; various device components, including the internal memory and processor, are connected to the system bus. The processor is hardware used to execute computer program instructions through basic arithmetic and logical operations within the computer system. Internal memory is a physical device used for temporary or permanent storage of computational programs or data (e.g., program state information). The system bus can be any of several types of bus architectures, including a memory bus or memory controller, a peripheral bus, and a local bus. The processor and internal memory can communicate via the system bus. Internal memory includes read-only memory (ROM) or flash memory (not shown in the figure), and random access memory (RAM), which typically refers to the main memory loaded with the operating system and computer programs.

[0075] Computer devices typically include an external storage device. The external storage device can be selected from a variety of computer-readable media, which are any usable media accessible by a computer device, including both removable and fixed media. Examples of computer-readable media include, but are not limited to, flash memory (microSD cards), CD-ROMs, digital versatile optical discs (DVDs) or other optical disc storage, magnetic tape cartridges, magnetic tapes, disk storage or other magnetic storage devices, or any other media that can be used to store desired information and is accessible by a computer device.

[0076] The computer device can be logically connected with one or more network terminals in a network environment. The network terminals can be personal computers, servers, routers, smart phones, tablet computers, or other public network nodes. The computer device is connected with the network terminals through a network interface (a local area network LAN interface). A local area network (LAN) refers to a computer network interconnected in a limited area, such as a family, a school, a computer laboratory, or an office building using network media. WiFi and twisted-pair wiring Ethernet are two commonly used technologies for building a local area network.

[0077] It should be noted that other computer systems including more or less subsystems than the computer device can also be suitable for the invention.

[0078] As described in detail above, the computer device suitable for the present embodiment can perform the specified operations of the radio signal simulation method. The computer device performs these operations by a processor running software instructions in a computer readable medium. These software instructions can be read into the memory from a storage device or from another device through a local area network interface. The software instructions stored in the memory cause the processor to perform the above-mentioned group member information processing method. In addition, the present invention can also be implemented by hardware circuitry or hardware circuitry combined with software instructions. Therefore, the implementation of the present embodiment is not limited to any specific combination of hardware circuitry and software.

[0079] Embodiment 2

[0080] The present embodiment proposes a USRP-based radio signal simulation device, including a data generation module, a modulation module, a data sampling module, and an interference superposition module.

[0081] The data generation module generates binary original data before sampling modulation corresponding to the message type according to the inquiry, response, or broadcast information type. The inquiry, response, or broadcast information type is dynamically controlled in the form of external input parameters.

[0082] The modulation module selects a modulation mode, modulates the binary original data, and generates I / Q modulation data.

[0083] The data sampling module samples the I / Q modulation data according to the sampling rate parameter, and generates I / Q sampling data.

[0084] The interference superposition module superimposes interference signals on the I / Q sampling data and then outputs to the radio frequency end for conversion output.

[0085] Further, the data generation module of the embodiment of the present application includes, but is not limited to, a MARK X / XII western system IFF interrogation data generation unit, a MARK X / XII western system IFF response data generation unit, an S-mode interrogation data generation unit, an S-mode response data generation unit, an ADS-B broadcast data generation unit, a DME interrogation data generation unit, a DME response data generation unit, and seven typical signal generation modules.

[0086] Further, the modulation module of the embodiment of the present application includes, but is not limited to, an ASK modulation unit, a DPSK modulation unit, and an AM modulation unit.

[0087] Further, the interference superposition module of the embodiment of the present application includes, but is not limited to, a white noise interference unit, a multipath interference unit, a co-frequency interference unit, and a monopulse interference unit.

[0088] Embodiment 3

[0089] The embodiment proposes a radio signal simulation system based on USRP, which includes the signal simulation device based on software implementation and the hardware device proposed in the above embodiment 2.

[0090] As shown in Figure 4 , the hardware device includes an FPGA (a master control unit), an AD9364 (a DAC unit), a DDR4 (a cache unit), and an MCU radio frequency channel management unit.

[0091] The FPGA, as the master control unit of the hardware module, can realize the control of frequency, wired / wireless power amplifier, output power, and data transmission. The FPGA is connected with the signal simulation device through a group of eight-channel buses PCIe. All data and control are completed through the data transmission and control of the bus. The data control and management of the AD9346 ADC / DAC, the data read / write of the DDR4, and the MCU radio frequency channel management are sent by the signal simulation device. Specifically, all data streams before DA conversion are completed on the computer in the form of DLL calling. The data after sampling and superimposing interference signals by the DLL are directly sent to the FPGA cache. The data in the FPGA cache are controlled to perform DA conversion and then output through the radio frequency channel.

[0092] The AD9346 communicates with the FPGA through an AXI bus to perform digital-to-analog conversion (DA conversion) on the data transmitted by the signal simulation device.

[0093] The DDR4 is used as a data storage address of the signal simulation device. The cache structure of the DDR4 is a ping-pong double cache mode.

[0094] The MCU radio frequency channel management unit is used to control and manage the transmission of the wireless radio frequency signal in the wireless transmission mode of the FPGA.

[0095] Embodiment 4

[0096] This embodiment takes S mode response signal simulation as an example to illustrate the technology proposed in the above embodiment, and the secondary radar S mode response signal simulation process is as follows:

[0097] 1. Set the S mode DF21 response link in the user interface of the upper computer, set the response signal wired transmission power to -40dBm, set the response signal frequency to 1000 times / s, set the DF21 message field (FS, DR, UM, ID, MB, AP field) value, and set the noise to white noise interference;

[0098] 2. Generate the binary response data of the S mode DF21 in step 1 according to the RTCA-DO-260B standard;

[0099] 3. Transmit the binary interrogation signal in step 2 into the ASK modulation module for modulation to obtain binary ASK modulation data;

[0100] 4. Sample the modulation data in step 3 according to the sampling clock to generate 1000 times of DF21 response IQ sampling data in 1 second;

[0101] 5. Superimpose white noise interference on the sampling data generated in step 4 to generate the final zero intermediate frequency IQ baseband data;

[0102] 6. Send a control instruction to the FPGA, and the FPGA sets the transmission power to -40dBm, the wired transmission mode, and the transmission frequency to 1030MHz;

[0103] 7. Send the baseband data generated in step 5 to the FPGA;

[0104] 8. The FPGA controls the transmission of the DF21 signal through internal logic and transmits the baseband data once per second.

[0105] The above specific embodiments further illustrate the purpose, technical solutions and beneficial effects of the present application. It should be understood that the above description is only a specific embodiment of the present application and is not used to limit the protection scope of the present application. Any modification, equivalent replacement, improvement, etc. within the spirit and principles of the present application should be included in the protection scope of the present application.

Claims

1. A method for simulating secondary surveillance radar and DME signals based on USRP, characterized in that, The method comprises the following steps: According to the inquiry, response or broadcast message type, generate the binary original data before sampling modulation of the corresponding message type; Using the corresponding modulation mode, modulate the binary original data to generate I / Q modulation data; According to the sampling rate parameter, data sample the I / Q modulation data to generate I / Q sampling data; After superimposing the interference signal on the I / Q sampling data, output to the radio frequency end for conversion output; The analog method is based on software defined radio technology, and the generation of the binary original data, I / Q modulation data, I / Q sampling data and interference signal superposition are realized by software, and the hardware is only responsible for realizing digital analog conversion, setting carrier frequency and carrier power setting.

2. The method of claim 1, wherein, The inquiry, response or broadcast message type is dynamically controlled in the form of external input parameter, and at least one data in (1)-(7) can be generated: (1) Pulse waveform data of western system IFF inquiry with parameters not sampled; (2) Pulse waveform data of western system IFF response with parameters not sampled; (3) Pulse waveform data of S mode inquiry with parameters not sampled; (4) Pulse waveform data of S mode response with parameters not sampled; (5) Pulse waveform data of ADS-B broadcast with parameters not sampled; (6) Pulse waveform data of DME inquiry with parameters not sampled; (7) Pulse waveform data of DME response with parameters not sampled.

3. The method of claim 2, wherein the USRP-based secondary radar and DME signal simulation method is characterized by, The external input parameter is used to calculate the value of each bit of the message packet, and each bit can be mapped to a preset pulse width, and the specific mapping rule is determined by different signal formats.

4. The method of claim 1, wherein, The modulation mode at least includes one of (1)-(3): (1) ASK modulation; (2) DPSK modulation; (3) AM modulation.

5. The method of claim 1, wherein, The superimposed interference signal at least includes one of (1)-(4): (1) White noise interference; (2) Multipath noise interference; (3) Monopulse interference; (4) Co-channel interference.

6. A USRP-based secondary surveillance radar and DME signal simulation device, characterized by, The method comprises: A data generation module generates binary original data before sampling modulation of the corresponding message type according to the inquiry, response or broadcast message type; A modulation module modulates the binary original data using the corresponding modulation mode to generate I / Q modulation data; A data sampling module data samples the I / Q modulation data according to the sampling rate parameter to generate I / Q sampling data; An interference superposition module superimposes the interference signal on the I / Q sampling data and then outputs to the radio frequency end for conversion output; The analog device is based on software defined radio technology, and the generation of the binary original data, I / Q modulation data, I / Q sampling data and interference signal superposition are realized by software, and the hardware is only responsible for realizing digital analog conversion, setting carrier frequency and carrier power setting.

7. The USRP-based secondary radar and DME signal simulation device of claim 6, wherein, The data generation module comprises a MARK X / XII western system IFF interrogation data generation unit, a MARK X / XII western system IFF response data generation unit, an S-mode interrogation data generation unit, an S-mode response data generation unit, an ADS-B broadcast data generation unit, a DME interrogation data generation unit and a DME response data generation unit.

8. The USRP-based secondary radar and DME signal simulation device of claim 6, wherein, The modulation module comprises an ASK modulation unit, a DPSK modulation unit and an AM modulation unit.

9. The USRP-based secondary radar and DME signal simulation device of claim 6, wherein, The interference superposition module comprises a white noise interference unit, a multipath interference unit, a co-frequency interference unit and a monopulse interference unit.

10. A USRP-based secondary surveillance radar and DME signal simulation system, characterized by, The USRP-based secondary radar and DME signal simulation device and the hardware device according to any one of claims 6-9 are comprised; The hardware device comprises a main control unit, a DA conversion unit, a cache unit and a radio frequency channel management unit; The simulation device transmits the data after sampling and superimposing the interference signal to the cache unit for caching, the main control unit controls the DA conversion unit to perform DA conversion on the data cached in the cache unit, and the DA-converted data is output by the radio frequency channel management unit.

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