A GNSS simulator radio frequency hardware simulation system

Abstract

The present invention proposes a GNSS simulator radio frequency hardware simulation system, which mainly includes a signal generating subsystem, a control subsystem, a self-marking subsystem, a time-frequency subsystem, an intermediate frequency chassis, a radio frequency chassis, a time-frequency chassis, a test chassis and other parts. The signal generating subsystem includes a digital signal processing unit, a radio frequency signal generating unit and a power division network and other parts, which directly outputs 42 radio frequency signals (including 30 multipath signals) for one user and conforms to the spatial signal characteristics, and requires that the power imbalance of the 42 radio frequency signals is less than 0.2dB. The control subsystem includes an Ethernet card, a transmitting memory network card and corresponding hardware and software platforms, which control the signal generating subsystem so that it acts according to the instructions of the real-time data, control and management and test and evaluation subsystems of the mathematical simulation, and controls the time-frequency subsystem to switch the internal and external frequency references.

Description

Technical Field

[0001] The invention belongs to the technical field of satellite simulation, and in particular relates to a GNSS simulator radio frequency hardware simulation system. Background Art

[0002] At present, since the Beidou Satellite Navigation System (BDS) was fully built, it has become an important source of information in the modern information society and an indispensable part of the national infrastructure in the information age due to its extremely high positioning capability and the ability to easily provide information such as location, time and speed. The application of satellite navigation has become more and more extensive, involving almost every aspect of people's lives.

[0003] In addition to the development of the BDS positioning system itself, the application of terminal products, which are the hallmark of the BDS industry, is also showing a rapid growth trend. This mainly includes satellite navigation signal simulators and satellite navigation positioning receivers. As a necessary test equipment, the successful development and achievable accuracy of satellite navigation signal simulators also play a vital role in the development process of receivers, providing a test simulation environment for satellite navigation receivers. At the same time, as my country continues to improve its development of its own Beidou satellite navigation and positioning system, the localization of satellite navigation-related technology products is becoming increasingly urgent. Therefore, the research on GNSS simulator technology has important reference significance and experience for my country's subsequent promotion of the Beidou satellite navigation system.

[0004] A satellite signal simulator is a test device that simulates the trajectory of satellite navigation signals. It can simulate signals in real time using live satellite frequency signals, or it can be manually configured to simulate satellite navigation signals in a desired navigation environment. During testing, a dedicated simulation model is established based on the actual verification environment to simulate the trajectory of a satellite receiver on a moving platform. Compared to testing in a real environment using actual GNSS signals, GNSS simulators provide an excellent alternative. Unlike real-world testing, testing with a GNSS signal simulator provides complete control over the simulated satellite signals and environmental conditions. Leveraging a GNSS signal source, users can generate a variety of scenarios and conduct a variety of test types.

[0005] As one of the most important components of a GNSS simulator, the RF hardware simulation system not only requires a signal generation system, a control system, an automatic calibration system, and a time-frequency system, but also requires the entire hardware simulation system equipment to be grouped and materialized. Due to the different divisions of labor among various systems, there are many uncertainties in the functional division of each subsystem and the differentiated deployment details of the equipment, which is also a major problem that needs to be overcome in the engineering application of GNSS simulators.

[0006] Therefore, there is an urgent need for a GNSS simulator radio frequency hardware simulation system. Summary of the Invention

[0007] The present invention proposes a GNSS simulator radio frequency hardware simulation system. Under the premise of being fully equipped with a signal generation system, a control system, an automatic calibration system, and a time-frequency system, the system is deployed through differentiated deployment. The common points are deployed on a general server and placed in a standard cabinet, while the special functions are deployed in a dedicated chassis such as an intermediate frequency chassis, a radio frequency chassis, a time-frequency chassis, and a test chassis. This greatly solves the problem of the physical application of the GNSS simulator device hardware system.

[0008] The technical solution of the present invention is implemented as follows: the present invention provides a GNSS simulator radio frequency hardware simulation system, which mainly includes a signal generation subsystem, a control subsystem, an automatic calibration subsystem, a time-frequency subsystem, an intermediate frequency chassis, a radio frequency chassis, a time-frequency chassis, a test chassis and other parts.

[0009] The signal generation subsystem includes a digital signal processing unit, a radio frequency signal generation unit, and a power splitter network. It directly outputs 42 radio frequency signals (including 30 multipath signals) for a single user that conform to spatial signal characteristics. The power imbalance of the 42 radio frequency signals is required to be less than 0.2dB.

[0010] The control subsystem includes an Ethernet card, a transmitting memory network card and corresponding hardware and software platforms, which controls the signal generation subsystem so that it acts according to the real-time data of mathematical simulation, the instructions of the control and management and test and evaluation subsystems, and controls the time-frequency subsystem to switch internal and external frequency references.

[0011] The self-calibration subsystem includes a test receiver, a universal test instrument, a switch matrix and a calibration cable, and completes the performance index calibration of the signal generation subsystem and the time-frequency subsystem.

[0012] The time-frequency subsystem includes a clock frequency synthesis, a high-stability crystal oscillator, a switch and a power divider, which completes the generation of constellation time-frequency reference and provides a unified time-frequency reference for the ground operation and control system simulation test system.

[0013] The intermediate frequency chassis includes a control subsystem and an intermediate frequency part of a signal generating system.

[0014] As a preferred embodiment, the intermediate frequency signal generation submodule is composed of a signal generation unit module, a global control unit module, a system timing unit module, a data communication unit module, and a data integration and distribution unit module.

[0015] Furthermore, the intermediate frequency signal generation submodule adopts the CPCI bus standard in the hardware architecture and adopts the CPCI board + PMC daughter board (mezzanine) solution to build a standardized, modular and scalable hardware system. The scale of the system can be expanded according to different needs.

[0016] The radio frequency chassis contains the radio frequency part of the signal generating subsystem.

[0017] As a preferred implementation, the RF chassis includes four units: up-conversion, power control, interference signal synthesis, and power division network, which mainly complete the functions of up-conversion, power control, and interference signal synthesis of the QPSK spread spectrum modulated signal input at the intermediate frequency.

[0018] Specifically, the chassis contains four identical up-conversion, power control, interference signal synthesis, and power splitter network units. Each unit performs frequency conversion, power control, interference signal synthesis, and signal splitting functions for a set of B1, B2, and B3 frequency signals to simulate RF signals.

[0019] The time-frequency chassis includes a time-frequency subsystem part.

[0020] As a preferred embodiment, the time-frequency subsystem includes a clock frequency synthesizer, a high-stability crystal oscillator, a switch, and a power divider. This generates a time-frequency reference signal, providing a unified time-frequency reference for the ground operation control system simulation test system. The reference signals include 10 MHz, 10.23 MHz, and 1 PPS. This subsystem also synthesizes various high-frequency clock signals required within the subsystem, primarily crystal oscillator signals and D / A clock signals. The 10 MHz, 10.23 MHz, and 1 PPS reference clocks can be selected between internal and external clocks.

[0021] The test chassis contains the test receiver in the self-calibration subsystem. The function of this test subsystem is to provide a test method for the RF hardware signal simulation subsystem, mainly completing the following three functions:

[0022] (1) Real-time signal tracking of the output signal of the signal simulator;

[0023] (2) Measure the key parameters of the output signal of the signal simulator as required;

[0024] (3) Collect the output signal of the signal simulator and store it for subsequent analysis and processing.

[0025] As a preferred embodiment, to provide greater flexibility at the receiver front end, analog-to-digital conversion is advanced, and the signal is sampled at the RF. This allows operations such as downconversion and narrowband filtering at various frequency points to be performed digitally, enhancing flexibility. Due to the sampling rate limitations of current ADC devices, only bandpass sampling (undersampling) is required for RF signals. The impact of undersampling is the folding of some frequency components. However, for test equipment, this folding does not cause significant information loss. It only causes noise aliasing when the input signal is not filtered. This loss is tolerable compared to the flexibility provided by RF sampling.

[0026] The sampled signal is digitally downconverted, and narrowband filtering is performed by filters after mixing. After mixing, the intermediate frequency signal is reduced to tens of MHz, eliminating the need for the high sampling rates of RF sampling. Downsampling the signal can reduce the data rate. Data storage and subsequent processing are performed on the downsampled signal, reducing bandwidth pressure for data acquisition.

[0027] The subsequent signal processing section uses the correlator structure of a common navigation receiver. The downsampled digital IF signal requires demodulation and despreading to extract the navigation message. In the receiver, a local reproduced carrier is generated and multiplied with the digital IF signal to demodulate the satellite signal. The local reproduced code is XORed with the input IF signal to achieve despreading. The despread signal is accumulated and judged, and then fed back into the reproduced carrier frequency, carrier phase, code phase, and other parameters to achieve satellite signal acquisition and tracking. After the signal is acquired, the bit stream is extracted. This module responsible for demodulation and despreading is called the correlation channel.

[0028] By interpreting the bit stream from the satellite, the system generates a navigation message. Based on user needs, the system uses the navigation message, current code phase, and Doppler information to calculate the current position, altitude, speed, and other results in real time.

[0029] As a preferred embodiment, the test subsystem consists of an RNSS signal simulator subsystem, an analog-to-digital converter module, a data acquisition module, a satellite signal capture and tracking module, a display / monitoring module, and a navigation information processing module.

[0030] As a preferred implementation, based on the requirements of various functions and the current hardware situation, the entire test subsystem can be further divided into a sampling / down-conversion module, a signal processing module, a navigation information processing module, a display / control module, a data acquisition module, etc.

[0031] After adopting the above technical solution, the beneficial effects of the present invention are:

[0032] 1. The GNSS simulator radio frequency hardware simulation system provided by the present invention is fully equipped with a signal generation system, a control system, a self-calibration system, and a time-frequency system. Through differentiated deployment, the common points are deployed on a general server and placed in a standard cabinet, while special functions are deployed in a dedicated chassis such as an intermediate frequency chassis, a radio frequency chassis, a time-frequency chassis, and a test chassis. This greatly solves the problem of the physical application of the GNSS simulator equipment hardware system.

[0033] 2. The GNSS simulator RF hardware simulation system provided by the present invention not only macroscopically expounds on the overall RF hardware simulation system deployment plan, but also fully demonstrates and analyzes the microscopic parts of the intermediate frequency chassis plan, RF chassis plan, time-frequency chassis plan, and test chassis plan based on the actual deployment situation, which greatly ensures the feasibility of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0035] Figure 1 This is a structural block diagram of a radio frequency hardware simulation system in an embodiment of the present invention;

[0036] Figure 2 This is a structural diagram of the intermediate frequency signal generation submodule in an embodiment of the present invention;

[0037] Figure 3 Schematic diagram of the functional structure of the test chassis test subsystem in an embodiment of the present invention;

[0038] Figure 4 This is a diagram showing the specific connection structure of the modules of the test chassis in an embodiment of the present invention. DETAILED DESCRIPTION

[0039] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0040] Example:

[0041] like Figures 1 to 4 As shown, the present invention provides a GNSS simulator radio frequency hardware simulation system, which mainly includes a signal generation subsystem, a control subsystem, an automatic calibration subsystem, a time-frequency subsystem, an intermediate frequency chassis, a radio frequency chassis, a time-frequency chassis, a test chassis and other parts.

[0042] In this embodiment of the present application, the signal generation subsystem includes a digital signal processing unit, an RF signal generation unit, and a power splitter network. It directly outputs 42 RF signals (including 30 multipath signals) for a single user that conform to spatial signal characteristics. The power imbalance of the 42 RF signals is required to be less than 0.2 dB.

[0043] In an embodiment of the present application, the control subsystem includes an Ethernet card, a transmitting memory network card and corresponding hardware and software platforms, which controls the signal generation subsystem so that it acts according to the real-time data of the mathematical simulation, the instructions of the control and management and the test and evaluation subsystems, and controls the time-frequency subsystem to switch the internal and external frequency references.

[0044] In the embodiment of the present application, the self-calibration subsystem includes a test receiver, a universal test instrument, a switch matrix and a calibration cable to complete the performance index calibration of the signal generation subsystem and the time-frequency subsystem.

[0045] In the embodiment of the present application, the time-frequency subsystem includes a clock frequency synthesis, a high-stability crystal oscillator, a switching switch and a power divider to complete the generation of constellation time-frequency reference and provide a unified time-frequency reference for the ground operation and control system simulation test system.

[0046] In the embodiments of the present application, the IF chassis includes a control subsystem and the IF portion of the signal generation system. The IF signal generation submodule consists of a signal generation unit module, a global control unit module, a system timing unit module, a data communication unit module, and a data integration and distribution unit module. The IF signal generation submodule utilizes the CPCI bus standard for its hardware architecture, employing a CPCI board + PMC mezzanine board solution to create a standardized, modular, and scalable hardware system that can be scaled to meet diverse needs.

[0047] Specifically, the detailed functions of each component module in the intermediate frequency signal generation submodule are as follows:

[0048] (1) Signal generation unit

[0049] Responsible for the generation of physical signals. Each signal generation unit is homogeneous and is used to generate intermediate frequency analog signals of multiple channels.

[0050] (2) Global control unit

[0051] According to the instructions of the control subsystem, the initial state of the RF hardware simulation test system is set, the working process of each signal generating unit is controlled, and the working condition information of each signal generating unit is received and fed back to the control subsystem.

[0052] (3) System timing unit

[0053] According to the input 1PPS second pulse, it establishes its own timing information and makes each signal generation unit work synchronously.

[0054] (4) Data communication unit

[0055] Receive mathematical simulation data, PRM encoding data and other information, and transmit the information to the data integration unit.

[0056] (5) Data integration and distribution unit

[0057] After comprehensive processing of simulation data information, coding information, timing information and other information, the data is distributed to each signal generation unit according to the identification information of the data.

[0058] In this embodiment of the present application, the RF chassis contains the RF portion of the signal generation subsystem. The RF chassis includes four units: upconversion, power control, interference signal synthesis, and a power splitter network. These units primarily perform upconversion, power control, and interference signal synthesis for the intermediate frequency input QPSK spread spectrum modulated signal. Specifically, the chassis contains four identical upconversion, power control, interference signal synthesis, and power splitter network units. Each unit performs frequency conversion, power control, interference signal synthesis, and signal splitting for a set of B1, B2, and B3 frequency point signals to simulate RF signals.

[0059] In the embodiment of the present application, the time-frequency chassis includes a time-frequency subsystem. The time-frequency subsystem includes a clock frequency synthesis, a high-stability crystal oscillator, a switching switch, and a power divider. It completes the generation of the time-frequency reference signal and provides a unified time-frequency reference for the ground operation control system simulation test system, including three frequency points: 10MHz, 10.23MHz, and 1PPS. At the same time, it synthesizes various high-frequency clock signals required within this subsystem, mainly crystal oscillator signals and D / A clock signals. The three reference clocks of 10MHz, 10.23MHz, and 1PPS can be selected between the internal clock and the external clock.

[0060] In this embodiment of the present application, the test chassis includes a test receiver in the self-calibration subsystem. The function of this test subsystem is to provide a test method for the RF hardware signal simulation subsystem, mainly completing the following three functions:

[0061] (1) Real-time signal tracking of the output signal of the signal simulator;

[0062] (2) Measure the key parameters of the output signal of the signal simulator as required;

[0063] (3) Collect the output signal of the signal simulator and store it for subsequent analysis and processing.

[0064] In an embodiment of the present application, to provide greater flexibility at the receiver front end, analog-to-digital conversion is advanced and the signal is sampled at RF. This allows operations such as down-conversion and narrowband filtering at various frequency points to be implemented digitally, thereby increasing flexibility. Due to the sampling rate limitations of current ADC devices, only bandpass sampling (undersampling) can be performed on the RF signal. The impact of undersampling is the folding of some frequency components. However, for test equipment, this folding does not cause serious information loss. It only causes noise aliasing when no filter is added to the input signal. This loss is tolerable compared to the flexibility brought by RF sampling.

[0065] The sampled signal is digitally downconverted, and narrowband filtering is performed by filters after mixing. After mixing, the intermediate frequency signal is reduced to tens of MHz, eliminating the need for the high sampling rates of RF sampling. Downsampling the signal can reduce the data rate. Data storage and subsequent processing are performed on the downsampled signal, reducing bandwidth pressure for data acquisition.

[0066] The subsequent signal processing section uses the correlator structure of a common navigation receiver. The downsampled digital IF signal requires demodulation and despreading to extract the navigation message. In the receiver, a local reproduced carrier is generated and multiplied with the digital IF signal to demodulate the satellite signal. The local reproduced code is XORed with the input IF signal to achieve despreading. The despread signal is accumulated and judged, and then fed back into the reproduced carrier frequency, carrier phase, code phase, and other parameters to achieve satellite signal acquisition and tracking. After the signal is acquired, the bit stream is extracted. This module responsible for demodulation and despreading is called the correlation channel.

[0067] By interpreting the bit stream from the satellite, the system generates a navigation message. Based on user needs, the system uses the navigation message, current code phase, and Doppler information to calculate the current position, altitude, speed, and other results in real time.

[0068] In the embodiment of the present application, the test subsystem is composed of an RNSS signal simulator subsystem, an analog-to-digital converter module, a data acquisition module, a satellite signal capture and tracking module, a display / monitoring module, and a navigation information processing module.

[0069] Specifically, the functional flow between the modules in the test subsystem is as follows:

[0070] 1) The signal from the RF signal simulation subsystem is directly fed into the ADC for digitization. After sampling, each frequency point undergoes digital down-conversion. The down-converted data is downsampled to reduce the data rate, and the downsampled output serves as the input for the signal processing module and data acquisition section.

[0071] 2) The down-converted signal needs to be stored in the hard disk for subsequent analysis and sent to the relevant channel to extract the navigation message. After packaging, the navigation information is processed and positioning solution and Kalman filter smoothing are performed. After the navigation information is processed, the positioning result is calculated.

[0072] 3) In addition, the parameter setting, result display, status monitoring and other operations of the entire subsystem need to be uniformly displayed and monitored to provide a good human-machine interface for test personnel to operate.

[0073] In the embodiment of the present application, the entire test subsystem can be further divided into a sampling / down-conversion module, a signal processing module, a navigation information processing module, a display / control module, a data acquisition module, etc., based on the requirements of each function and the current hardware situation. Specifically, the detailed functions of each module are as follows:

[0074] 1) Sampling / down-conversion module: completes analog-to-digital conversion, and implements digital down-conversion, narrowband filtering, downsampling, and other operations at three frequencies;

[0075] 2) Signal processing module: Each frequency point is divided into several channels, and each channel performs operations such as carrier reproduction, carrier stripping, code reproduction, accumulation, search, and judgment to achieve functions such as signal tracking, message extraction, and Doppler measurement;

[0076] 3) Navigation information processing module: receiving navigation messages, bit stream interpretation, pseudo-range measurement, positioning solution, Kalman filtering and other operations;

[0077] 4) Display / control module: centrally displays positioning results and current status, sets system parameters, provides human-machine interface, etc.

[0078] 5) Data acquisition module: collects intermediate frequency data and stores it in the hard disk for subsequent analysis.

[0079] In an embodiment of the present application, the data channels between the sampling / down-conversion module, the signal processing module, and the navigation information processing module are interconnected using the standard LINK interface of the RDIPS hardware universalization system. The display / control module is interconnected with other modules using the PCI bus. The data acquisition module receives data through the PCI bus and stores the data in the hard disk.

[0080] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A GNSS simulator radio frequency hardware simulation system, characterized in that: Including signal generation subsystem, control subsystem, self-calibration subsystem, time-frequency subsystem, intermediate frequency chassis, radio frequency chassis, time-frequency chassis and test chassis to exchange data with each other; The signal generation subsystem includes a digital signal processing unit, a radio frequency signal generation unit, and a power division network part, which directly outputs 42 radio frequency signals for one user and conforms to the spatial signal characteristics, wherein the power imbalance of the 42 radio frequency signals is less than 0.2dB; The control subsystem includes an Ethernet card, a transmitting memory network card and corresponding software and hardware platforms, which controls the signal generation subsystem to make it operate according to the real-time data of the mathematical simulation, the instructions of the control and management and test and evaluation subsystems, and controls the time-frequency subsystem to switch the internal and external frequency references; The self-calibration subsystem includes a test receiver, a universal test instrument, a switch matrix and a calibration cable, and completes the performance calibration of the signal generation subsystem and the time-frequency subsystem; The time-frequency subsystem includes a clock frequency synthesis, a high-stability crystal oscillator, a switch and a power divider to complete the generation of the constellation time-frequency reference; The intermediate frequency signal of the intermediate frequency chassis control subsystem and the signal generating system; The radio frequency chassis controls the signal generation subsystem's radio frequency signal; The time-frequency chassis controls the time-frequency signals of the time-frequency subsystem; The test chassis includes a test receiver in a self-calibration subsystem.

2. A GNSS simulator radio frequency hardware simulation system according to claim 1, characterized in that: The intermediate frequency signal generation submodule in the intermediate frequency chassis is composed of a signal generation unit module, a global control unit module, a system timing unit module, a data communication unit module, and a data integration and distribution unit module.

3. A GNSS simulator radio frequency hardware emulation system as claimed in claim 2, characterized in that: The intermediate frequency signal generation submodule adopts CPCI bus standard in hardware architecture, and adopts CPCI board + PMC subboard.

4. A GNSS simulator radio frequency hardware simulation system according to claim 1, characterized in that: The radio frequency chassis includes four units: up-conversion, power control, interference signal synthesis, and power division network. The radio frequency chassis controls the up-conversion, power control, and interference signal synthesis of the QPSK spread spectrum modulated signal input by the intermediate frequency.

5. A GNSS simulator radio frequency hardware emulation system as claimed in claim 4, characterized in that: Four identical up-conversion, power control, interference signal synthesis, and power division network units are installed in the RF chassis. Each unit completes the frequency conversion, power control, interference signal synthesis, and signal branching functions of a group of B1, B2, and B3 frequency point signals to simulate RF signals.

6. A GNSS simulator radio frequency hardware simulation system according to claim 1, characterized in that: The time-frequency subsystem includes clock frequency synthesis, high-stability crystal oscillator, switching switch and power divider. The time-frequency subsystem completes the generation of time-frequency reference signal, and provides a unified time-frequency reference for the ground operation control system simulation test system, including three frequency points of 10MHz, 10.23MHz and 1PPS. At the same time, it synthesizes various high-frequency clock signals, crystal oscillator signals and D / A clock signals required in this subsystem. The three reference clocks of 10MHz, 10.23MHz and 1PPS can be selected between internal clock and external clock.

7. The GNSS simulator radio frequency hardware simulation system according to claim 1, characterized in that: The test receiver in the test chassis tracks the output signal of the signal simulator in real time, measures key parameters of the output signal of the signal simulator, collects the output signal of the signal simulator, and stores it for analysis and processing.

8. The GNSS simulator radio frequency hardware simulation system according to claim 1, characterized in that: The test subsystem consists of an RNSS signal simulator subsystem, an analog-to-digital converter module, a data acquisition module, a satellite signal capture and tracking module, a display / monitoring module, and a navigation information processing module.

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