Method and device for processing signals of navigation satellites gps and glonass

 

(57) Abstract:

A method of processing signals of navigation satellites GPS and GLONASS and analog processor designed for use in Radiotracker simple cheap integrated satellite navigation receivers operating on signals from GPS satellites (USA) and GLONASS (Russia). The operation of the frequency conversion signal is produced using a heterodyne frequency, which is located between the spectra of GPS and GLONASS and selected in accordance with the expression fNGPS< fG< fNGLONASSwhere fHGPS- carrier frequency signals NAVSTAR GPS, fG- frequencies, fHGLONASS- carrier frequency of the least used letter in the GLONASS system, and the bandwidth of the amplifier common to the signals of both systems. The receiver does not contain items that relate to one of these systems, receives and processes the signals of these different systems as signals of one system. The proposed receiver contains a minimal number of functional elements for processing signals of one of the systems, the antenna receiving the signals of the navigation satellite systems, Shirokogorov, analog-to-digital Converter whose output is the input of the digital receiver system receiver, inputs of the amplifier with limited bandwidth. The technical result consists in the fact that the proposed device is an extremely simplified radio link. There are no items requiring configuration in the production process. In addition, the proposed frequency plan radio greatly facilitates and simplifies the construction of the synthesizer heterodyne frequency and subsequent digital processing, and a wide end-to-end bandwidth radio increases the measurement accuracy of the pseudorange. 2 S. and 1 C.p. f-crystals, 1 Il.

The invention relates to the field of radio, and in particular navigation using signals of satellite navigation systems GPS and GLONASS.

The proposed method and the device can be used in tracts of primary information processing receiver-indicators two satellite navigation systems GPS and GLONASS (crns).

Known methods of processing radio signals of navigation satellites GPS and GLONASS, which use a multi-channel system for processing radio signals. Also known Ana is m GPS (USA) and GLONASS (Russia), construction of multi-channel scheme. Analog processors contain at least two separate foster tract, have several elements in common only the heterodyne synthesizer frequencies.

Each of these paths includes their input filter preselector, low noise amplifier, one or more local oscillators, one or more filters and amplifiers, intermediate frequency (if) and analog-to-digital Converter. The common element of these receive paths is a reference crystal oscillator, as for example in [1].

Another way and the option of constructing an analog processor (patent [2]) involves the use of a broadband input circuits of the high frequency transmitting to the mixer bandwidth covering the spectra of the signals of both systems: GPS and GLONASS (1574,42-1621 MHz) is split into two identical foster tract, starting from the mixer, which converts the incoming signal into two quadrature components by use of signals lo, shifted in phase by 90o. Each of the quadrature channels contains the filter, intermediate frequency amplifier and analog-to-digital Converter.

Also known to the receiver [3], in which the analog processor soda is salanie signal into two quadrature components. The output of this receiver are the outputs of the four identical analog-to-digital converters.

The disadvantage of all of these receivers is their hardware redundancy, resulting in deterioration of the accuracy characteristics, complicated and expensive equipment consumers in General.

The requirement to increase the accuracy characteristics of the receiver pulse signals requires broadband radiotracked. The bandwidth extension high-frequency up to several tens of megahertz merging bandwidth of the input filter signals satellite systems GPS and GLONASS, which both improves the accuracy characteristics of the receivers for each of the systems will lead to significant simplification of the integrated receiver by eliminating duplication of receive paths.

A method of processing signals of navigation satellites GPS and GLONASS, which includes operations broadband filtering, broadband amplification, frequency conversion using heterodyne frequency received from the synthesizer heterodyne frequency, broadband gain intermediate frequency, an analog-to-digital transformation is the creation, containing the antenna receiving the signals of the navigation satellite systems, broadband filter, a broadband low noise amplifier, mixer, synthesizer heterodyne frequency reference oscillator, analog-to-digital Converter whose output is the input of the digital receiver system receiver. The known method and apparatus are implemented in a receiver of signals of satellite radio navigation systems [4], which is the closest prototype of the proposed device.

The advantage of the receiver [4] is the ability to work with two signals of satellite radio navigation systems - GPS and GLONASS. This provides a sufficiently high measurement accuracy navigation parameters.

However, the device prototype has a number of disadvantages.

in the prototype, the frequency of the local oscillator is located far enough to the left of the carrier frequency of the GPS, which leads to the introduction of advanced second low-noise amplifier, the first and second bandpass filters at intermediate frequencies, different for GPS and GLONASS, block automatic gain control.

in the prototype, the use of separate filters the intermediate frequency for signal is subramania is a simplified analogue circuit combined receiver dvuhsotmetrovyh systems GPS and GLONASS.

Along with a substantial simplification of the whole path is achieved the maximum possible end-to-end broadband radio, which in combination with the known method strobe correlator reduces the measurement error of the pseudorange caused by multipath propagation of radio signals.

The essence of the method consists in the following.

These advantages over the prototype is achieved due to the fact that in the proposed method converts the frequency of the signal produced using the heterodyne frequency, which is located between the spectra of GPS and GLONASS and selected in accordance with the expression

fHGPS< fG< fNGLONASS,

where fNGPS- carrier frequency signals NAVSTAR GPS,

fG- frequency local oscillator (lo)

fNGLONASS- carrier frequency of the least used letter in the GLONASS system,

thus the bandwidth of the amplifier common to the signals of both systems and no additional selection signals of these systems is not required.

In the analog processor of the receiver, containing the antenna receiving the signals of the navigation satellite systems, broadband filter, Sezimovo Converter, the output of which is input of the digital receiver system receiver, inputs of the amplifier with limited bandwidth, the broadband filter connected to the antenna output, and the output to the input of a broadband low-noise amplifier, the output of which is connected to the first input of the mixer, the second input of which is connected to the output of the synthesizer heterodyne frequency, the input of the heterodyne synthesizer frequency is connected to the output of the reference oscillator, the mixer output is connected to the input of the amplifier with limited bandwidth, the output of which is input analog-to-digital Converter whose outputs are the inputs of the digital radio receiving system, and the last input connected to the output of the reference oscillator.

It is this mutual arrangement of blocks and their interconnections provide a solution to the technical objectives.

Unambiguous tracking PLL bearing is ensured by the choice of the nominal lo frequency so that the intermediate frequencies band GPS signals with the highest possible values of Doppler shift and differences of the frequencies of the generators of the satellite and receiver do not overlap with similar polomalu GLONASS. From this point of view suitable are any integer values of lo frequencies in megahertz. On the other hand, this frequency should be placed as close as possible to the sum of the frequencies of GPS and average lettered GLONASS that any finite bandwidth of the amplifier will provide the maximum possible end-to-end broadband entire tract. In addition, to simplify the synthesizer in the digital part of the receiver preferably, this frequency is not a multiple step lettered frequency GLONASS (0,5625 MHz). The optimal frequency value is the value of 1590 MHz.

When building a PLL carrier (or in the secondary processing of results of measurements) should be borne in mind that the signs are being tracked by the PLL frequency deviations from nominal values opposite to GPS and GLONASS.

Thus, the technical result of the proposed method is achieved by the location of the lo frequency between the carrier frequencies of the radio signals, as well as the introduction of advanced amplifier with limited bandwidth, location of known blocks and interconnections between the blocks.

Functional diagram of the proposed receiver is shown in Fig. 1, where 1 is the antenna receiving synesael, 5 - heterodyne synthesizer frequency, 6 - amplifier with limited bandwidth, 7 - reference generator 8 - analog-to-digital Converter whose output is the input of the digital receiver system receiver 9.

The broadband input filter 2 is connected to the output of the antenna 1, and the output to the input of a broadband low-noise amplifier 3, the output of which is connected to the first input of the mixer 4, the second input of which is connected to the output of the heterodyne synthesizer frequency 5. The input of the synthesizer heterodyne frequency 5 is connected to the output of the reference oscillator 7, the output of the mixer 4 is connected to the input of the amplifier with limited bandwidth 6 whose output is the input of the analog-to-digital Converter 8 whose outputs are the inputs of the digital radio receiving system 9, and the last input connected to the output of the reference oscillator 7.

The signal from antenna 1, the receiving signals of the two satellite systems (GPS and GLONASS) is broadband input filter 2, a broadband low-noise amplifier 3 and is supplied to the signal input of the mixer 4. On heterodyne input of this mixer comes heterodyne frequency signal 1590 MHz synthesizer 5.

The sub-signal is antennas bandwidth, an upper cut-off frequency response of at least 50 MHz. Wide bandwidth, just the radio circuit is a necessary condition for improving the accuracy characteristics of the receiver, including reducing the measurement error range caused by multipath propagation of satellite signals (band in tens of megahertz would reduce these errors to centimeter level).

Amplified by the amplifier signal is fed to a three-tier (two stroke) additive analog-to-digital Converter, is able to significantly suppress in-band continuous interference, which largely compensates for the loss of noise immunity caused by broadband radio and mirror TV reception.

Bibliography:

1. Description receiver 3S-Navigation", AGARDLS-207, C. 3-1 - 3-28, June 1996;

2. Patent RU N 2067770;

3. The application of Ukraine N 98105418 15.10.98 for "Method and device hardware digital processing of radio navigation satellites NAVSTAR GPS and GLONASS.

4. Patent RU N 2110149 from 25.05.1993, "a Receiver of signals of satellite radio navigation systems".

1. A method of processing signals of navigation satellites GPS and GLONASS, including paragraph is whether the heterodyne frequency, received from the synthesizer heterodyne frequency, broadband gain intermediate frequency and digital signal processing, characterized in that the operation of the broadband gain of the intermediate frequency perform analog-digital conversion of the signals from the output of the amplifier with limited bandwidth, and the operation of the frequency conversion signal is produced using a heterodyne frequency, which is located between the spectra of GPS and GLONASS and selected in accordance with the expression

fHGPS< fG< fNGLONASS,

where fHGPS- carrier frequency of the GPS signals NAVSTSR;

fGthe frequency of the local oscillator;

fNGLONASS- carrier frequency of the least used letter in the GLONASS system,

thus the bandwidth of the amplifier common to the signals of the two systems.

2. The method according to p. 1, characterized in that the frequency of the local oscillator is selected in accordance with the terms under item 1 and is 1590 MHz.

3. The processing unit of the radio signals of satellite navigation systems GPS NAVSTSR and GLONASS containing the antenna receiving the signals of the navigation satellite systems, broadband Phi is tax-digital Converter and a digital radio receiving system, characterized in that it additionally introduced amplifier with limited bandwidth, the broadband filter connected to the antenna output and the output to the input of a broadband low-noise amplifier, the output of which is connected to the first input of the mixer, the second input of which is connected to the output of the synthesizer heterodyne frequency, the input of the heterodyne synthesizer frequency is connected to the output of the reference oscillator, the mixer output is connected to the input of the amplifier with limited bandwidth, the output of which is input analog-to-digital Converter, and inputs the digital radio receiving system connected respectively to the outputs of the analog-to-digital Converter and the reference oscillator.

 

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