WO2007140725A1

WO2007140725A1 - A navigation satellite signal processing system

Info

Publication number: WO2007140725A1
Application number: PCT/CN2007/070064
Authority: WO
Inventors: Hansheng Wang; Junlin Zhang
Original assignee: Olinkstar Corporation, Ltd.
Priority date: 2006-05-31
Filing date: 2007-05-29
Publication date: 2007-12-13
Also published as: CN1862284A

Abstract

A navigation satellite signal processing system includes a signal acquisition device, and the signal acquisition device has a computer interface whose data transmission rate is greater than 12Mbit/s. The adoption of the system can implement real-time, continuous and long-period acquisition of navigation satellite signal, and can directly transfer the signal data into the computer.

Description

Navigation satellite signal processing system

Technical field

The invention belongs to the field of satellite navigation, in particular to a navigation satellite signal processing system, which generally comprises a signal acquisition device and a signal playback device, and is an effective tool for developing a satellite navigation receiver. The system converts the navigation satellite RF signal into an intermediate frequency signal with a lower carrier frequency, and then samples it into data, and then transmits the data to the computer through the standard USB2.0 interface. The system can acquire navigation satellite signals in real time, continuously and for a long time. Developers can use these data to study the algorithms, structures and procedures of satellite navigation receivers or to develop satellite navigation software receivers. At the same time, the system can also receive the data of the computer through the standard USB2.0 interface, and then transmit the radio frequency signal of the navigation satellite to verify and debug the satellite navigation receiver. The navigation satellite signal processing system of the present invention can be applied to the acquisition and playback of any navigation satellite signal, including the GPS system of the United States, the GLONASS system of Russia, the Galileo system of Europe, the Beidou system of China, and any new ones that may appear in the future. Satellite navigation system. 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 calculates the position of the receiver based on the received satellite signals. The general satellite navigation system consists of multiple satellites distributed in different orbital planes to ensure that multiple satellite signals can be received at any time within the application range, such as for GPS (Global Positioning System). System) The application of the system is global, and it is guaranteed that at least four satellites can be received at any time and anywhere in the world. The satellite navigation receiver is a device that receives satellite signals and calculates the position, time, and speed based on the received satellite signals.

Figure 1 is a block diagram of the satellite navigation receiver. 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 waves of the navigation satellites in the space into electrical signals, and the frequency of the signals is the satellite signal band. For example, the frequency of the L1 band of the GPS system is 1575.42 MHz. The radio frequency part amplifies, downconverts, filters, digital-to-analog the navigation satellite signal, and finally outputs the digital signal. Downconversion refers to the reduction of signals in the satellite band (typically 1 GHz to 2 GHz) to intermediate frequency signals of several MHz to several tens of MHz. The intermediate frequency signals can be further processed by signals. The filtering section is a bandpass filter that filters out-of-band noise. The digital-to-analog conversion converts the down-converted and filtered intermediate-frequency analog signal into a digital signal, which can be further processed by digital signals. The baseband processing is generally a digital circuit that processes the IF digital signal from the radio frequency portion. The main function is to remove the direct spread sequence and the intermediate frequency carrier. The software part runs on the embedded processor and performs operations based on the results of the baseband processing part. Write control parameters to the baseband processing section. 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. Because satellite navigation receivers generally use embedded processors, it is more difficult to debug software directly on embedded processors. It is more difficult to study algorithms. In the debugging environment, you can't see a lot of intermediate signals or data. The more common methods are: digitizing the down-converted navigation satellite signals into data and transmitting them to the computer through software. The data contains all the information and features of the navigation satellite signals, but the carrier frequencies are different. The software fully emulates the entire software portion of the satellite navigation receiver and the baseband processing portion of the hardware to study the algorithm, structure and procedures of the receiver. In addition, the same data acquisition device is required if a software satellite navigation receiver is to be developed (i.e., the baseband processing portion and the software portion of the receiver are implemented entirely in software). At present, only one foreign company (Accord Software & System, Inc.) produces such a navigation satellite signal data acquisition device, and its block diagram is shown in Figure 2. The antenna converts the electromagnetic signals of the navigation satellite into electrical signals. The navigation satellite signal is amplified, downconverted, and filtered by low noise. At this time, the frequency of the signal is not the satellite signal band, but becomes an intermediate frequency signal with a carrier frequency of several MHz to several tens of MHz. The IF signal is amplified again, analog-to-digital converted, and becomes data. The data is temporarily stored in the memory. When the data is collected, the data is read from the memory and transmitted to the computer through the USB1.1 interface. The USB 1.1 interface is a standard computer interface with a data rate of 12 Mbit/s. The local clock oscillator is used as the clock source for the local carrier in the downconversion and the sampling clock for the analog to digital conversion. Although this kind of acquisition device can realize the acquisition function of navigation satellite signals to a certain extent, it still has the following deficiencies. 1. The interface speed of USB1.1 is 12Mbit/s. If the extra overhead bit in the transmission is removed, the maximum transmission rate can only reach 1MB/S, and the rate of the general navigation satellite IF signal data is several MB/s to more than ten MB/ s, much higher than the speed of the USB1.1 interface. Therefore, the device can only temporarily store the data in the memory, and then stop the data acquisition, and then transfer the data in the memory to the computer through the USB1.1 interface. In this way, the data acquisition time is limited by the memory capacity. If 256MB of memory is used, only tens of seconds of data can be collected, and data of several minutes or hours cannot be collected. If the sampling rate is high or the number of bits per sample is large, the acquisition time is even shorter; 2. Since the device transmits data to the computer after the data acquisition is completed, the device cannot be used to develop real-time. Software receiver; 3, the device can not play back the collected data or generated data; 4, no external clock source input, can not control the IF carrier frequency and data sampling rate. Summary of the invention

The present invention is directed to a defect or deficiency in the prior art, and provides a navigation satellite signal processing system, The system can acquire navigation satellite signals in real time, continuously and for a long time, and does not need temporary memory to store the signal data collected in real time, but directly transmits the signal data to the computer. Through further improvement, the system also has digital, intermediate frequency, and RF playback functions, which can play back the collected data or generated data stored in the computer. In addition to the local oscillator, there is an external clock input for selection, which can be controlled. IF carrier frequency and data sampling rate.

The technical idea of the present invention is to improve the navigation satellite signal processing mode of "data storage and then transfer" in the prior art to a direct transmission mode by using a computer high-speed data interface, thereby realizing real-time, continuous, long-time acquisition and navigation. Satellite signals, and the temporary memory can be omitted.

The technical scheme of the present invention is as follows:

The navigation satellite signal processing system comprises a signal acquisition device, characterized in that: the signal acquisition device has a computer interface with a data transmission rate greater than 12 Mbit/s.

The data transmission rate of the computer interface is not less than 20 Mbit/s.

The computer interface is a USB 2.0 interface.

Also included is a signal playback device for playing back the acquired data or the generated data.

The signal playback device has the functions of digital playback, intermediate frequency playback, and/or radio frequency playback.

It also includes two clock sources to choose from, one for the local oscillator and one for the external clock input.

The external clock input can be used to control the IF carrier frequency and data sampling rate of the acquired signal, and/or to control the RF frequency and playback data rate of the playback signal.

The technical effects of the present invention are as follows:

The navigation satellite signal processing system of the present invention is an effective tool for developing a satellite navigation receiver. The system converts the navigation satellite radio frequency signal into an intermediate frequency signal with a lower carrier frequency, and then samples it into data, and then transmits the data to the computer through a standard USB2.0 interface. The system can acquire navigation satellite signals in real time, continuously and for a long time. Developers can use these data to study the algorithms, structures and procedures of satellite navigation receivers or to develop satellite navigation software receivers. At the same time, the system can also receive the data of the computer through the standard USB2.0 interface, and then transmit the radio frequency signal of the navigation satellite to verify and debug the satellite navigation receiver. DRAWINGS

Figure 1 is a block diagram of the components of a satellite navigation receiver.

2 is a schematic block diagram of a navigation satellite signal data acquisition device in the prior art.

3 is a schematic block diagram of a navigation satellite signal processing system of the present invention, including a signal acquisition device and a signal playback device. detailed description

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

The invention aims to solve the deficiencies of the above-mentioned navigation satellite signal acquisition device, and proposes a new navigation satellite signal acquisition and playback system. The system adopts high-speed standard computer interface, such as USB2.0 interface (up to 480Mb/s), without memory, can transmit data to the computer continuously, in real time and for a long time. In addition, the system also has digital, intermediate frequency and radio frequency. The playback function can play back the collected data or generated data stored in the computer. In addition to the local oscillator, there is an external clock input for selection, which controls the IF carrier frequency and data sampling rate.

As shown in FIG. 3, FIG. 3 is a schematic block diagram of a navigation satellite signal processing system of the present invention, including a signal acquisition device and a signal playback device. The main features are: no temporary memory; high-speed data interface, continuous, real-time, long-term acquisition of signals, high-speed data interface including USB2.0 and other standard computer high-speed data interface; with digital, intermediate frequency, RF three playback functions , you can also play back the signal continuously, in real time, for a long time. When digital playback is performed, the clock frequency of the playback digital signal can be arbitrarily set, that is, the data rate of the digital playback can be arbitrarily set. In the acquisition and playback device, there is an external clock input, and the local oscillator and external clock can be optionally used as the clock source.

In the navigation satellite signal acquisition part, the antenna converts the electromagnetic wave signal of the navigation satellite into an electrical signal, and the frequency of the signal is the satellite signal band. The navigation satellite signal is amplified, down-converted, and filtered by low noise. At this time, the frequency of the signal is not the satellite signal band, but becomes an intermediate frequency signal with a carrier frequency of several MHz to several tens of MHz. The IF signal is then amplified, analog-to-digital converted, and converted to data. Data is transferred directly to the computer via a computer-standard high-speed data interface. If the USB2.0 interface is used, it will be encoded by USB2.0 and encoded into USB2.0 format according to the USB2.0 protocol. USB2.0 has a maximum speed of 480 Mbit/s, eliminating the necessary overhead and a data transfer rate of 50 MB/s. If the sampling rate is 16MHz and the number of bits per sample is 2 bits, the data rate of the navigation satellite signal is 4MB/s. The USB2.0 interface can meet the requirements, even if the sampling rate and the number of bits are increased. Claim.

The navigation satellite signal playback process is equivalent to the inverse of the acquisition process. The data files in the computer are read out and the data is transferred to the playback portion via a computer standard high speed data interface (such as a USB 2.0 interface). The data file can be the data collected by the acquisition system or the software-generated data. The data generation has the flexibility to generate signals of any scene and verify the performance of the receiver. In the playback system, the intermediate frequency digital signal is obtained through computer standard high-speed data decoding, and the digital signal can also be output as digital playback. The digital playback signal includes a signal clock and signal data, and the number of bits of the data is arbitrary, and may be one bit (that is, only one data line) or multiple bits (that is, there are multiple data lines). The frequency of the signal clock can be arbitrarily set, that is, the data rate can be arbitrarily set, making the debugging of the receiver more convenient. The digital playback signal can be used as the intermediate frequency signal input baseband processing part of the satellite navigation receiver for tuning Try and verify the rest of the receiver except the RF section. After the IF digital signal is digital-analog converted and filtered, it becomes an analog IF signal, and the analog IF signal can also be output as an intermediate frequency playback. The analog IF signal is upconverted and amplified to become a radio frequency signal of the navigation satellite band, and the RF signal output is radio frequency playback. The RF playback output is identical to the navigation satellite signal and can be used to debug and verify a complete satellite navigation receiver. The playback section can perform digital playback, IF playback, and RF playback in real time, continuously, and for a long time.

In the navigation satellite signal acquisition and playback system, there are two clock sources, one is the clock generated by the local oscillator, and the other is the external clock input. You can choose one of them. The selected clock is used as the clock source of the local carrier in the down-conversion and the sampling clock of the analog-to-digital conversion in the acquisition system. In the playback system, it is used as the data clock of the digital-to-analog conversion and the clock source of the modulated carrier in the up-conversion. The external clock input accurately controls the IF carrier frequency and data sampling rate of the acquired signal, as well as the RF frequency and playback data rate of the playback signal.

This equipment is suitable for the collection and playback of various navigation satellite signals, including the US GPS system, the European Galileo system, the Russian GLONASS system, etc., and the new satellite navigation system that may appear in the future, which can be real-time, continuous and long-term. It can acquire navigation satellite signals without temporary memory, and has functions such as digital playback, IF playback, and RF playback. It can also play back navigation satellite signals in real time, continuously and for a long time. It is a research, verification and development of satellite navigation receivers and satellite navigation software. An effective tool for the receiver.

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 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

A navigation satellite signal processing system, comprising a signal acquisition device, characterized in that: the signal acquisition device has a computer interface having a data transmission rate greater than 12 Mbit/s.

The navigation satellite signal processing system according to claim 1, wherein: the data transmission rate of the computer interface is not less than 20 Mbit/s.

3. The navigation satellite signal processing system according to claim 2, wherein: said computer interface is a 1^2.0 interface.

4. The navigation satellite signal processing system according to claim 1, further comprising: signal playback means for playing back the collected data or the generated data.

The navigation satellite signal processing system according to claim 4, wherein: said signal playback device has functions of digital playback, intermediate frequency playback, and/or radio frequency playback.

6. The navigation satellite signal processing system of claim 5, further comprising: an optional two clock sources, one being a clock generated by a local oscillator and the other being an external clock input.

7. The navigation satellite signal processing system according to claim 6, wherein: said external clock input is operable to control an intermediate frequency carrier frequency and a data sampling rate of the collected signal, and/or to control a radio frequency and playback of the playback signal. Data rate.