WO2008089637A1

WO2008089637A1 - A navigation satellite signal generating system based on the software

Info

Publication number: WO2008089637A1
Application number: PCT/CN2007/071078
Authority: WO
Inventors: Hansheng Wang; Junlin Zhang
Original assignee: Olinkstar Corporation, Ltd.
Priority date: 2007-01-19
Filing date: 2007-11-16
Publication date: 2008-07-31
Also published as: CN101033974B; CN101033974A

Abstract

A navigation satellite signal generating system based on software includes a software part and a hardware part which are connected by a computer interface. The software part is running in the computer, and the software in the computer generates the digital intermediate frequency signal of the navigation satellite.

Description

Software-based navigation satellite signal generation system

Technical field

The invention relates to the field of satellite navigation, in particular to a software-based navigation satellite signal generation system, which is an effective tool for developing and testing a satellite navigation receiver, and can be applied to the generation of any navigation satellite signal. These include the US GPS system, the Russian GLONASS system, the European Galileo system, China's Beidou system, and any new satellite navigation systems that may emerge in the future. Background technique

A satellite navigation system is a system in which a plurality of navigation satellite signals are received by a receiver, and the receiver performs operations based on the received navigation satellite signals to obtain a receiver position. The general satellite navigation system consists of multiple navigation satellites distributed in different orbital planes to ensure that any navigation satellite can receive signals from any location within the application at any time, such as the current US GPS (Global Positioning). System Global Positioning System) The system is used worldwide to ensure that at least four navigation satellites can be received at any time, anywhere in the world. The satellite navigation receiver is a device that receives the navigation satellite signal and calculates the position, time, and speed according to the received satellite signal.

Figure 1 is a block diagram of a satellite navigation system and a satellite navigation receiver. The satellite navigation receiver can simultaneously receive the signals transmitted by n navigation satellites. The sum of the n navigation satellite signals is called the navigation satellite radio frequency signal S _RF:

SRFI = Ai G (t - ij ) Di (t) sin(cOi (t - ij ) + Φ; ) + 3⁄4 (t) (2)

Among them, S _RFi is the radio frequency signal of the i-th satellite, the signal amplitude of the i-th satellite, C t) is the i-th satellite pseudo-random code, including all codes in various navigation satellite systems, such as the US GPS system. C/A code, P code, various codes in the Galileo system, etc., D t) Navigation message transmitted for the i-th satellite, including various messages in various navigation satellite systems, _{ω ί} is the i-th The carrier angular frequency of the satellite, including all frequencies in various navigation satellite systems, is the carrier phase of the i-th satellite, ^ is the transmission delay of the i-th satellite, and _ni (t) is the noise power. , _{T i} , _ni (t) and the navigational orbit of the navigation satellite, the error parameters such as the clock error of the navigation satellite, navigation satellite signal transmission error parameters (such as ionospheric error, tropospheric error), channel attenuation, receiver position and motion state That is, when the receiver is in different positions and different motion states, it will cause corresponding changes in the above variables. Satellite navigation receivers usually consist of two parts: hardware and software. The hardware part includes the antenna, the RF section, and the baseband processing. The antenna converts the electromagnetic wave of the navigation satellite in the space into an electrical signal to obtain a radio frequency signal, and the frequency of the signal is a satellite signal band. For example, the frequency of the L1 band of the GPS system is nominally 1575.42 MHz. The radio frequency part amplifies, downconverts, filters, digital-to-analog the navigation satellite signal, and finally outputs the digital intermediate frequency signal. Downconversion is the analog IF signal that reduces the satellite band signal (typically 1 GHz to 2 GHz) to a few MHz to tens of MHz, which is equivalent to the frequency of the RF signal minus a fixed local oscillator frequency. The analog IF signal S _IFA is:

SlFA =∑S _IFAi (3) i=l

SiFAi = Ai G (t _ ^ ) Di (t _ η ) sin((cOi - ω ₀ )(ί - ) + + n^t) (4) where ω. The local oscillator angular frequency. The digital-to-analog conversion is to sample and quantize the down-converted analog intermediate frequency signal S _IFA to become a digital intermediate frequency signal, and the digital intermediate frequency signal S _IFD can be further digitally processed. The baseband processing is generally a digital circuit that processes the digital intermediate frequency signal. The main function is to remove the direct spread sequence and the intermediate frequency carrier. The software portion runs on the processor, performs operations based on the results of the baseband processing portion, and simultaneously writes control parameters to the baseband processing portion. The software part consists of two parts: signal processing and solving. Signal processing software mainly includes satellite signal acquisition, tracking, bit synchronization, bit information extraction and other parts. The main function of the solution part is to calculate the receiver position.

At present, the development and development of satellite navigation receivers is a time-consuming and laborious task. In order to comprehensively study the algorithms of satellite navigation receivers and test their performance, the receivers need to be in any position and in any motion state, and need any time and any time. Various conditions such as signal strength and arbitrary transmission error. However, it is impossible to make the receiver truly under these conditions (especially some extreme environments) during actual development and testing. Therefore, a navigation satellite signal generation system (or a navigation satellite signal simulator) is required to artificially generate a navigation satellite radio frequency signal S _RF , so that various parameters in equations (1) and (2) correspond to various conditions, such as time, channel. Attenuation, receiver position and motion state, channel transmission delay, etc., so that various environmental conditions can be simulated under static conditions in the laboratory to verify and test the navigation satellite receiver. Figure 2 is a schematic block diagram of the existing navigation satellite signal generation system. The user can arbitrarily set various parameters such as the position and motion trajectory of the receiver, time, error parameters, channel attenuation, etc. The signal generation system calculates each navigation satellite report. And the carrier frequency, carrier frequency change rate, carrier phase, delay, etc. of each navigation satellite received by the receiver, generating control commands, controlling the hardware part for direct spreading sequence generation, direct spreading sequence spreading, carrier Generate, carrier modulation, adjust the gain, and finally generate the navigation satellite RF signal S _RF . The software portion of the system is typically run in a dedicated computer system. Although the above structure is adopted by all current navigation satellite signal generation systems in the market, it has the following disadvantages: 1. Main functions (such as direct spread sequence generation, direct spread sequence spread spectrum, carrier generation, carrier adjustment, etc.) Through hardware implementation, the equipment is complex and costly; 2. Once the hardware of the equipment is completed, it is difficult to change, the flexibility is poor, and it is difficult to upgrade or renovate. For example, if a new navigation satellite system or a new satellite signal appears, new equipment is needed; 3, the output is single, only the RF signal, no The method obtains the analog intermediate frequency signal and the digital intermediate frequency signal; 4. The digital intermediate frequency signal data cannot be obtained, and the data can be processed by computer software for data analysis and software simulation; 5. The special computer system has high cost and poor flexibility; 6. due to hardware The implementation is too complicated, and it is not convenient to design a hybrid navigation satellite signal generation system with multiple satellite navigation systems, multiple codes, and multiple frequency points. 7. It is difficult to expand the function, and the user cannot add a custom signal to the output signal, such as single frequency interference. Signals, etc. Summary of the invention

The present invention is directed to a software-based navigation satellite signal generation system capable of requiring less hardware, thereby reducing cost, but having increased flexibility, in view of the deficiencies or deficiencies in the prior art.

The technical idea of the present invention is that the digital intermediate frequency signal data of the navigation satellite is generated by software in a computer, thereby reducing the units of direct spread sequence spreading, carrier generation and carrier modulation in the hardware configuration, and achieving low cost and high flexibility. Software-based navigation satellite signal generation system.

The technical scheme of the present invention is as follows:

A software-based navigation satellite signal generation system, comprising a software part and a hardware part connected by a computer data interface, wherein: the software part runs in a computer, and the digital intermediate frequency signal data of the navigation satellite is generated by the software in the computer .

The digital intermediate frequency signal data is transmitted to the hardware portion through a computer data interface to obtain a digital intermediate frequency signal; the digital intermediate frequency signal is subjected to digital-to-analog conversion and filtering to obtain an analog intermediate frequency signal; and the analog intermediate frequency signal is up-converted to obtain a radio frequency signal of the navigation satellite.

The computer data interface is a standard computer data interface, including a USB interface or a PCI interface.

The hardware portion mainly includes a digital-to-analog conversion device, a filtering device, an up-conversion device, and a gain control device, and does not include a direct-spread sequence spreading device, a carrier generating device, and a carrier modulation device.

The digital-to-analog conversion, filtering, and up-conversion are performed into a plurality of parallel channels, so as to obtain navigation satellite signals of various navigation satellite systems, various codes, and various frequencies respectively, and finally combine the radio frequency signals of all channels to obtain the final RF signal.

The digital intermediate frequency signal can be directly input to the baseband portion of the satellite navigation receiver for debugging and testing, and the clock frequency of the digital intermediate frequency signal can be arbitrarily set, that is, the clock frequency can be different from the actual sampling rate; The analog intermediate frequency signal can be input to the analog to digital conversion portion of the satellite navigation receiver for debugging and testing; the power of the radio frequency signal can be adjusted by the gain control device, and the radio frequency signal can be input to the complete satellite navigation receiving Machine for debugging and testing.

The intermediate frequency, the sampling rate, and the number of sample bits in the digital intermediate frequency signal data generated by the software can be set by software. The software portion also includes a custom signal module that can be extended by the user, ie the user can add a custom signal.

The technical effects of the present invention are as follows:

The invention proposes a new software-based navigation satellite signal generation system with only minimal and basic hardware, low cost and high flexibility. The system mainly generates digital intermediate frequency signal data through an ordinary computer, and then transmits it to the hardware part through a standard computer data interface, such as a USB interface (up to 480 Mb/s), a PCI interface, etc., to obtain a digital intermediate frequency signal, and then undergoes digital modulo The analog IF signal is transformed, and finally the RF signal is obtained by up-conversion. The system can obtain various output forms such as digital intermediate frequency signal data, digital intermediate frequency signal, analog intermediate frequency signal, and radio frequency signal.

The navigation satellite signal generation system is an effective tool for developing satellite navigation receivers. Different from the current hardware-based navigation satellite signal generation system, the present invention is a software-based navigation satellite signal generation system, and the digital intermediate frequency signal data of the navigation satellite is generated by software in a computer, and the hardware part only retains the least part, that is, the main mode only Number conversion, band pass filtering and upconversion. The digital intermediate frequency signal data is transmitted from the computer to the hardware device through a standard computer data interface, so that the digital intermediate frequency signal of the navigation satellite can be obtained. After the digital-to-analog conversion, the analog intermediate frequency signal can be obtained, and then up-converted, the navigation satellite can be obtained. The RF signal, which is exactly the same as the navigation satellite signal in actual conditions. The system is flexible in structure, strong in scalability, and low in cost. It can generate radio frequency signals, analog intermediate frequency signals, digital intermediate frequency signals, and digital intermediate frequency signal data of navigation satellites. Developers can use these signals to research, verify, and test satellite navigation receiver algorithms. , program and performance. DRAWINGS

Figure 1 is a block diagram of a satellite navigation system and a satellite navigation receiver.

2 is a schematic block diagram of a conventional navigation satellite signal generation system.

3 is a schematic block diagram of a software-based navigation satellite signal generation system of the present invention. detailed description

The invention will be further described in detail below with reference to the accompanying drawings.

3 is a schematic block diagram of a software-based navigation satellite signal generation system of the present invention, which is mainly divided into a software part and a hardware part.

The software part of the navigation satellite signal generation system runs on a common computer. The user can arbitrarily set the position and motion trajectory of the receiver through the human-machine interface, as well as various parameters such as time, error parameters, channel attenuation, etc. Errors, including navigation satellite orbit parameters, navigation satellite clock error parameters, ionospheric parameters, tropospheric parameters, etc. With these parameters, a navigation message can be obtained. Using these parameters and the receiver's motion trajectory, the receiver can be received The observations of the respective navigation satellites include parameters such as intermediate frequency carrier frequency, carrier frequency change rate, carrier phase, code clock frequency, code phase, signal amplitude noise power, and the like, that is, parameters in the foregoing background technology formula (4). Using the formula (4), the digital intermediate frequency signal S _IFD data is finally obtained by software, which can be set by software, and the data can include any navigation satellite system, any code, satellite signal of any frequency, or generate a wide-area enhanced satellite signal, such as WAAS. , EGN0S signal, etc. Among them, the IF frequency, the sampling clock frequency, and the number of bits per sampling point can be set by software. In addition, it can have an extended function, users can add custom signals, such as single-frequency interference signals, to the digital IF signal to facilitate interference and anti-interference research. All previous functions were implemented in software. Digital IF signal data can also be used by users for data analysis and software simulation.

The computer reads the digital intermediate frequency signal data and transmits it to the hardware part of the navigation satellite signal generation system through a standard computer data interface. The transmission bit rate of the standard computer data interface should be greater than the sampling rate of the digital intermediate frequency signal. X bits of each sampling point. The data interface includes a USB, PCI interface, and the like. In the hardware part, the digital intermediate frequency signal is obtained by decoding the computer data interface. The digital intermediate frequency signal can be directly input to the baseband portion of the satellite navigation receiver for debugging and testing. The clock frequency of the digital intermediate frequency signal can be arbitrarily set, that is, the clock frequency can be different from the actual sampling rate. For example, for experimental verification, the satellite navigation receiver is going to perform an FPGA experiment. The speed of the receiver is lower than the actual situation. This can be done by inputting a low-frequency digital intermediate frequency signal. The digital intermediate frequency signal is digitally converted and filtered to obtain an analog intermediate frequency signal. The analog intermediate frequency signal can also be input to the analog-to-digital conversion part of the satellite navigation receiver for debugging and testing. The analog IF signal can be up-converted to obtain the radio frequency signal of the navigation satellite, and the power of the radio frequency signal can be adjusted by the gain control part. Among them, digital-to-analog conversion, filtering, and up-conversion can also be multiple parallel channels, so as to obtain navigation satellite signals of various navigation satellite systems, various codes, and various frequencies, and finally combine the RF signals of all channels, and then Get the final RF signal. This RF signal can be input to a complete satellite navigation receiver for commissioning and testing.

The invention is applicable to signal generation of various navigation satellite systems, including the GPS system in the United States, the Galileo system in Europe, the GLONASS system in Russia, the Beidou system in China, and the like, and new satellite navigation systems and new satellite signals that may appear in the future. , only need a normal computer and a small amount of hardware. The device hardware is simple (mainly including computer data interface circuit, analog-to-digital conversion, filter, up-conversion and gain control), low cost, high flexibility, easy to upgrade, and can output various navigation satellite systems and various codes separately or in combination. , navigation satellite signals of various frequencies. The output form is diversified, and digital intermediate frequency signal data, digital intermediate frequency signal, analog intermediate frequency signal, and radio frequency signal can be obtained. It is an effective tool for researching, verifying, developing, testing satellite navigation receivers and satellite navigation software receivers.

The software-based navigation satellite signal generation system of the present invention has the following features: 1. The navigation satellite signal generation system of the present invention can be applied to the generation of any navigation satellite signal, including the United States.

GPS systems, Russia's GLONASS system, Europe's Galileo system, China's Beidou system, and any new satellite navigation systems that may emerge in the future.

2. As shown in Figure 3, it is the main component block diagram of the navigation satellite signal generation system. The main features are: The main function is realized by software, the hardware part only keeps the least part; The digital IF signal data is generated by software in the ordinary computer; The standard computer data interface can transmit signals continuously and in real time, the standard computer data interface includes USB etc. All standard computer data interfaces, as long as the transmission bit rate of the data interface is greater than the sampling rate of the digital intermediate frequency signal X, the number of bits per sampling point; the hardware part mainly only digital-to-analog conversion, filtering, up-conversion, gain control.

3. Various output forms, such as digital intermediate frequency signal data, digital intermediate frequency signal, analog intermediate frequency signal, and radio frequency signal, or only one or several of digital intermediate frequency signal data, digital intermediate frequency signal, analog intermediate frequency signal, and radio frequency signal .

4. In the hardware part, you can include all or part of the 2 columns, or you can add or subtract combinations according to the functional requirements.

5. In the hardware part, digital-to-analog conversion, filtering, and up-conversion can also be multiple parallel channels to obtain various navigation satellite systems, various codes, navigation satellite signals of various frequencies, and finally combine the RF signals of all channels. , you can get the final RF signal.

6. The IF frequency, sampling rate, and number of sample bits in the digital IF signal data generated by the software can be set by software.

7. In the hardware part, when the digital intermediate frequency signal data transmitted from the computer becomes a digital intermediate frequency signal, the clock frequency of the digital intermediate frequency signal can be arbitrarily set.

8. The system can generate navigation satellite signals of multiple frequencies.

9. The system can generate various satellite navigation systems, multiple or separate navigation satellite signals.

10. The application can be extended by the user, and the user can add a customized signal.

11. The present system may also generate wide area enhanced satellite signals, such as WAAS, EGN0S signals, etc. It should be noted that the above-described embodiments may enable those skilled in the art to more fully understand the present invention, but do not limit the present invention in any way. . Accordingly, the present invention has been described in detail herein with reference to the drawings and the embodiments of the invention The technical solutions and their improvements should be covered by the scope of protection of the present invention.

Claims

Rights request

A software-based navigation satellite signal generation system, comprising a software part and a hardware part connected by a computer data interface, wherein: the software part runs in a computer, and the digital intermediate frequency of the navigation satellite is generated by the software in the computer Signal data.

2 . The software-based navigation satellite signal generation system according to claim 1 , wherein: the digital intermediate frequency signal data is transmitted to a hardware portion through a computer data interface to obtain a digital intermediate frequency signal; and the digital intermediate frequency signal undergoes digital-to-analog conversion. And filtering to obtain an analog intermediate frequency signal; the analog intermediate frequency signal is up-converted to obtain a radio frequency signal of the navigation satellite.

The software-based navigation satellite signal generating system according to claim 1, wherein: the computer data interface is a standard computer interface, and comprises a USB interface or a PCI interface.

The software-based navigation satellite signal generating system according to claim 1, wherein: the hardware portion mainly comprises a digital-to-analog conversion device, a filtering device, an up-conversion device, and a gain control device, and no longer includes direct expansion. A sequence spread spectrum device, a carrier generation device, and a carrier modulation device.

The software-based navigation satellite signal generating system according to claim 4, wherein: the digital-to-analog conversion, filtering, and up-conversion are performed into a plurality of parallel channels, so as to obtain various navigation satellite systems and various codes respectively. The navigation satellite signals of various frequencies, and finally the RF signals of all channels are combined to obtain the final RF signal.

6. The software-based navigation satellite signal generation system according to claim 2, wherein: said digital intermediate frequency signal can be directly input to a baseband portion of a satellite navigation receiver for debugging and testing, and a digital intermediate frequency signal. The clock frequency can be arbitrarily set, that is, the clock frequency can be different from the actual sampling rate; the analog intermediate frequency signal can be input to the analog-to-digital conversion portion of the satellite navigation receiver for debugging and testing; The power can be adjusted by a gain control device that can be input to a complete satellite navigation receiver for debugging and testing.

The software-based navigation satellite signal generating system according to claim 1, wherein: the intermediate frequency, the sampling rate, and the number of sample bits in the digital intermediate frequency signal data generated by the software are set by software.

8. The software-based navigation satellite signal generation system according to claim 1, wherein: the software portion further comprises a custom signal module, which can be extended by the user, that is, the user can add a customized signal.