GNSS simulator radio frequency hardware simulation system

Abstract

The invention provides a radio frequency hardware simulation system of a GNSS simulator. The radio frequency hardware simulation system mainly comprises a signal generation subsystem, a control subsystem, a self-standard subsystem, a time frequency subsystem, an intermediate frequency case, a radio frequency case, a time frequency case, a test case and the like. The signal generation subsystem comprises a digital signal processing unit, a radio frequency signal generation unit, a power division network and the like, and is used for directly outputting 42 paths of radio frequency signals (including 30 paths of multipath signals) which aim at a user and conform to spatial signal characteristics, and the power imbalance of the 42 paths of radio frequency signals is required to be less than 0.2 dB; and the control subsystem comprises an Ethernet card, a transmitting memory network card and a corresponding software and hardware platform, and is used for controlling the signal generation subsystem, so that the signal generation subsystem acts according to real-time data of mathematical simulation and instructions of the control, management and test and evaluation subsystem, and controlling the time frequency subsystem to switch 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 is the symbol of the industry, is also showing a rapid growth trend, mainly including satellite navigation signal simulators and satellite navigation positioning receivers. Among them, the satellite navigation signal simulator is a necessary test equipment. Its successful development and the accuracy it can achieve also play a vital role in the development process of the receiver, and can provide a test simulation environment for satellite navigation receivers. At the same time, as my country continues to improve its independent Beidou satellite navigation and positioning system, the localization of satellite navigation related technology products is becoming more and more urgent. Therefore, the research on GNSS simulator technology has great reference significance and experience reference 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 in real time according to real-time satellite frequency signals, or it can simulate satellite navigation signals in the required navigation environment through manual settings. During the test, a set of dedicated simulation models is established according to the actual verification environment to simulate the same trajectory as the satellite receiver on the motion platform environment. Compared with tests conducted in real environments using actual GNSS signals, GNSS simulators can provide an excellent alternative. Unlike real tests, tests using GNSS signal simulators can fully control simulated satellite signals and simulated environmental conditions. Using GNSS signal sources, users can generate a variety of scenarios and implement various types of tests.

[0005] As one of the most important components of a GNSS simulator, the RF hardware simulation system not only needs to have a signal generation system, a control system, a self-calibration system, and a time and frequency system, but also needs to group and materialize the entire hardware simulation system equipment. Since the division of labor of each system is different, 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 generating system, a control system, a self-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 special functions are deployed using a medium 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 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.

[0009] The signal generation subsystem includes a digital signal processing unit, a radio frequency signal generation unit, and a power division network, and directly outputs 42 radio frequency signals (including 30 multipath signals) for one user that meet the spatial signal characteristics, and 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 instructions of the real-time data, control and management and test and evaluation subsystems of mathematical simulation, and controls the time-frequency subsystem to switch internal and external frequency references.

[0011] The self-calibration subsystem comprises 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 switching 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 implementation, 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 subboard (mezzanine) solution to build a standardized, modular and expandable hardware system. The scale of the system can be expanded according to different needs.

[0016] The radio frequency chassis includes 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 division network units. Each unit completes the frequency conversion, power control, interference signal synthesis, and signal splitting functions of a group of B1, B2, and B3 frequency point signals to simulate RF signals.

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

[0020] As a preferred implementation, the time-frequency unit includes clock frequency synthesis, high-stability crystal oscillator, switching switch and power divider to complete the generation of time-frequency reference signal, and provide 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, various high-frequency clock signals required in this subsystem are synthesized, 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.

[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, and mainly complete the following three functions:

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

[0023] (2) Measure 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 implementation, in order to make the receiver more flexible at the front end, the analog-to-digital conversion is advanced here, and the signal is sampled at the radio frequency, so that operations such as down-conversion and narrowband filtering at each frequency point can be implemented by digital methods to improve flexibility. Due to the limitation of the sampling rate of the current ADC device, only bandpass sampling (undersampling) can be performed on the radio frequency signal. The impact caused by undersampling is to cause the folding of some frequency components, but as a test device, this folding will not cause serious information loss, but will cause noise aliasing when the input signal is not filtered. This loss is tolerable relative to the flexibility brought by radio frequency sampling.

[0026] The sampled signal is down-converted using digital methods, and the narrowband filtering of the signal is implemented in the filter after mixing. After mixing, the intermediate frequency signal is reduced to tens of megahertz, and the sampling rate as high as that of RF sampling is no longer required. The signal can be down-sampled to reduce the data rate. Data storage and post-processing are all for the down-sampled signal, which also reduces the bandwidth pressure of data acquisition.

[0027] The post-stage signal processing part adopts the correlator structure of an ordinary navigation receiver. The downsampled digital intermediate frequency signal needs to be demodulated and despread in order to extract the navigation message. A local reproducing carrier is generated in the receiver and multiplied with the digital intermediate frequency signal to realize the demodulation of the satellite signal. The local reproducing code and the input intermediate frequency signal are XORed to realize despreading. The despread signal is accumulated and judged, and then fed back to the reproducing carrier frequency, carrier phase, code phase and other parameters to realize the capture and tracking of satellite signals. After capturing the signal, the bit stream is extracted. This part of the module used for demodulation and despreading is called the correlation channel.

[0028] By interpreting the bit stream from the satellite, the navigation message is obtained. According to user needs, the navigation message, current code phase and Doppler information are used to calculate the current position, altitude, speed and other results in real time.

[0029] As a preferred embodiment, 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.

[0030] As a preferred implementation, according to the requirements of various functions and the current hardware conditions, 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. A 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-standard system, and a time-frequency system. Through differentiated deployment, the common points are deployed on a general server and placed in a standard cabinet, and special functions use a medium frequency chassis, a radio frequency chassis, a time-frequency chassis, and a test chassis. Dedicated chassis deployment, which greatly solves the problem of physical application of the GNSS simulator device hardware system.

[0033] 2. The GNSS simulator RF hardware simulation system provided by the present invention not only explains the overall RF hardware simulation system deployment plan at a macro level, but also fully demonstrates and analyzes the micro parts of the intermediate frequency chassis plan, RF chassis plan, time-frequency chassis plan, and test chassis plan according to 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 drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. 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 creative labor.

[0035] Figure 1 It 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 an intermediate frequency signal generation submodule in an embodiment of the present invention;

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

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

[0039] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are 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 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.

[0042] In the embodiment of the present application, the signal generation subsystem includes a digital signal processing unit, a radio frequency signal generation unit, and a power division network, and directly outputs 42 radio frequency signals (including 30 multipath signals) for one user that meet the spatial signal characteristics, and requires that the power imbalance of the 42 radio frequency signals is less than 0.2dB. ;

[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 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.

[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 indicator 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 the constellation time-frequency reference and provide a unified time-frequency reference for the ground operation and control system simulation test system.

[0046] In the embodiment of the present application, the intermediate frequency chassis includes a control subsystem and an intermediate frequency part of a signal generating system. The intermediate frequency signal generating submodule is composed of a signal generating 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 intermediate frequency signal generating submodule adopts the CPCI bus standard in the hardware architecture, and adopts the CPCI board + PMC subboard (mezzanine) solution to build a standardized, modular, and scalable hardware system. The scale of the system can be expanded according to different 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 isomorphic 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 the embodiment of the present application, the RF chassis includes the RF part of the signal generation subsystem. 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 by the intermediate frequency. Specifically, the chassis contains four identical up-conversion, power control, interference signal synthesis, and power division network units. Each unit completes the frequency conversion, power control, interference signal synthesis, and signal splitting functions of a group 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 unit includes a clock frequency synthesis, a high-stability crystal oscillator, a switching switch and a power divider to complete the generation of the time-frequency reference signal, and provide 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, various high-frequency clock signals required in this subsystem are synthesized, 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 the 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, and mainly complete the following three functions:

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

[0062] (2) Measure 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 the embodiment of the present application, in order to make the receiver more flexible at the front end, the analog-to-digital conversion is advanced here, and the signal is sampled at the radio frequency, so that operations such as down-conversion and narrowband filtering of each frequency point can be implemented by digital methods to improve flexibility. Due to the limitation of the sampling rate of the current ADC device, only bandpass sampling (undersampling) can be performed on the radio frequency signal. The impact caused by undersampling is to cause the folding of some frequency components, but as a test device, this folding will not cause serious information loss, but will cause noise aliasing when the input signal is not filtered. This loss is tolerable relative to the flexibility brought by radio frequency sampling.

[0065] The sampled signal is down-converted using digital methods, and the narrowband filtering of the signal is implemented in the filter after mixing. After mixing, the intermediate frequency signal is reduced to tens of megahertz, and the sampling rate as high as that of RF sampling is no longer required. The signal can be down-sampled to reduce the data rate. Data storage and post-processing are all for the down-sampled signal, which also reduces the bandwidth pressure of data acquisition.

[0066] The post-stage signal processing part adopts the correlator structure of an ordinary navigation receiver. The downsampled digital intermediate frequency signal needs to be demodulated and despread in order to extract the navigation message. A local reproducing carrier is generated in the receiver and multiplied with the digital intermediate frequency signal to realize the demodulation of the satellite signal. The local reproducing code and the input intermediate frequency signal are XORed to realize despreading. The despread signal is accumulated and judged, and then fed back to the reproducing carrier frequency, carrier phase, code phase and other parameters to realize the capture and tracking of satellite signals. After capturing the signal, the bit stream is extracted. This part of the module used for demodulation and despreading is called the correlation channel.

[0067] By interpreting the bit stream from the satellite, the navigation message is obtained. According to user needs, the navigation message, current code phase and Doppler information are used 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 directly enters the ADC for digitization, and after sampling, each frequency point is digitally down-converted. After down-conversion, the data is down-sampled to reduce the data rate, and the down-sampled output is used as the input of the signal processing module and the data acquisition part.

[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 the positioning solution and Kalman filter smoothing operations 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 displayed and monitored in a unified manner, providing a good human-machine interface for test personnel to operate.

[0073] In the embodiment of the present application, according to the requirements of each function 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. Specifically, the detailed functions of each module are as follows:

[0074] 1) Sampling / down-conversion module: completes analog-to-digital conversion, realizes digital down-conversion, narrow-band filtering, down-sampling 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 signal tracking, message extraction, Doppler measurement, and other functions;

[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 display positioning results and current status, set system parameters, provide 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 the 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 universal 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 principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A GNSS simulator radio frequency hardware simulation system, characterized in that: It includes signal generation subsystem, control subsystem, self-marking subsystem, time-frequency subsystem, intermediate frequency chassis, radio frequency chassis, time-frequency chassis and test chassis, which 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, and directly outputs 42 radio frequency signals for one user and conforming 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, controls the signal generation subsystem to make it act according to the instructions of the real-time data of the mathematical simulation, the control and management and the 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 index 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 switching 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 signal 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 as claimed in claim 1, characterized in that: The intermediate frequency signal generating submodule in the intermediate frequency chassis is composed of a signal generating 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 simulation 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 as claimed in 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 modulation signal input by the intermediate frequency.

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

6. A GNSS simulator radio frequency hardware simulation system as claimed in claim 1, characterized in that: The time-frequency unit includes clock frequency synthesis, high-stable crystal oscillator, switching switch and power divider. The time-frequency unit completes the generation of time-frequency reference signal, provides unified time-frequency reference for the ground operation control system simulation test system, including three frequency points of 10MHz, 10.23MHz and 1PPS, and simultaneously 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. A GNSS simulator radio frequency hardware simulation system as claimed in 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. A GNSS simulator radio frequency hardware simulation system as claimed in claim 1, characterized in that: The test subsystem consists of the RNSS signal simulator subsystem, analog-to-digital converter module, data acquisition module, satellite signal capture and tracking module, display / monitoring module, and navigation information processing module.

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