RU183917U1 - RADIO NAVIGATION SYSTEM SIGNAL FREQUENCY MONITORING DEVICE - Google Patents

Abstract

The utility model relates to radio navigation, namely to devices for tracking signal parameters and is intended to track the frequency of the navigation signal transmitted by the reference station of the radio navigation system in the primary signal processing unit of consumer equipment on a moving object. The technical result is to reduce the likelihood of disruption in tracking the frequency of the signal of the reference station of the radio navigation system over a time interval sufficient to obtain an estimate of the delay with the required accuracy when exposed to noise interference. The technical result is achieved by reducing the fluctuation component of the variance of the frequency filtering error when monitoring the signal frequency as a result of the correlation processing of the received signal and noise mixture.The proposed construction of the device circuit allows reducing the fluctuation filtering error of the frequency of the received signal by increasing the signal-to-noise ratio at the output of the device correlator. 1 ill.

Description

The utility model relates to radio navigation, to devices for tracking signal parameters and can be used in primary signal processing paths of equipment of consumers of radio navigation systems.

A device for automatically adjusting the frequency of a phase-shifted signal is known (RF Patent No. 2089047, IPC ⁷ H04L 27/22, H03D 13/00, publ. 08.27.1997, BI: No. 6, 2002), comprising a multi-channel correlator, a reference multiphase generator, a driver signal, decoder, primary and secondary memory blocks, phase difference direction discriminator and control signal shaper. The known device has insufficient noise immunity when exposed to intentional noise interference.

A device for phase-locked loop when tracking the phase of a phase-shifted signal (Lindsay V. Synchronization systems in communication and control / translation from English under the editorship of Yu.N. Bakaev, MV Kapranov. - M.: Soviet radio, 1978, p. 100-101), containing the first output of the device in series, the first filter, the ideal quadrator, the narrow-band pass filter, the first multiplier, the second filter, the adder, the loop generator, the frequency divider into two, the second multiplier, the detector, the second output of the device, and also third out d device, the second input of the first multiplier connected to the output of the loop oscillator, a second input of the adder - the third output device and the second input of the second multiplier - to the output of the first filter.

In this device, the input signal is squared, and then filtered by a narrow-bandpass filter tuned to double the frequency. For phase self-tuning of the local oscillator frequency, a classical phase-locked loop is used, operating at twice the frequency of the input signal. To generate a local oscillator signal coherent with the input signal, the output signal of the controlled loop generator is divided by a frequency divider into two.

The disadvantage of this device phase-locked loop is the low noise immunity when the signal to noise ratio at the input is less than unity.

A device for tracking the frequency of a signal is known, which is the device closest to the utility model and taken as a prototype (GLONASS. Principles of construction and operation / Edited by A.I. Perov, V.N. Kharisov. Ed. 4th, rev. and add. - M .: Radio Engineering, 2010, p. 511), containing the first, second, third, fourth, fifth, sixth, mixers; controlled digital signal generator (hereinafter referred to as the controlled frequency generator); 3-bit shift register (hereinafter referred to as the code generator); the first and second accumulative adders with reset (hereinafter - integrators); the first and second delay blocks by T (hereinafter referred to as delay blocks); adder; smoothing filter; the first, second and third outputs of the device.

In this case, the first inputs of the first and second mixers are connected to the second output of the device, the second inputs to the first and second outputs of the controlled frequency generator, respectively, and their outputs to the first inputs of the third and fourth mixers, respectively, the second inputs of which are connected to the output of the code generator, the input which is connected to the first output of the device, and their outputs to the inputs of the first and second integrators, respectively. The output of the first integrator is connected to the second input of the sixth mixer and the input of the first delay unit, the output of which is connected to the first input of the fifth mixer. The output of the second integrator is connected to the second input of the fifth mixer and the input of the second delay unit, the output of which is connected to the first input of the sixth mixer. The outputs of the fifth and sixth mixers are connected respectively to the first and second inputs of the adder, the output of which is connected to the input of the smoothing filter, the output of which is connected to the second control input of the controlled frequency generator, the first input of which is connected to the third output of the device.

The disadvantage of this device is the low noise immunity when exposed to noise interference, the level of which at the input of the device exceeds the signal level no less than the size of the base of the range-finding code of the navigation signal.

The problem to which the claimed utility model is directed is to increase the signal-to-noise ratio at the output of the correlator of the signal frequency tracking device.

The technical result is to increase noise immunity.

The technical result is achieved in that in a device containing a series-connected first and third mixers, a first integrator, a first delay unit and a fifth mixer; the second and fourth mixers connected in series, the second integrator, the second delay unit and the sixth mixer; serially connected adder, smoothing filter, controlled frequency generator; code generator; the first, second and third outputs of the device, with the first inputs of the first and second mixers connected to the second output of the device, the first inputs of a controlled frequency generator and code generator connected respectively to the third and first outputs of the device, the output of the code generator connected to the second inputs of the third and fourth mixers, the outputs of the first and second integrators are connected to the second inputs of the sixth and fifth mixers respectively, the outputs of which are connected to the second and first inputs of the adder, respectively two additional mixers are added, the output of the device and their connection.

The technical result is achieved by introducing 2 new blocks (seventh and eighth mixers) and their connections, which leads to a decrease in the fluctuation component of the variance of the frequency filtering error at the output of the smoothing filter of the device when tracking the signal frequency of the reference station as a result of correlation processing of the received signal mixture and noise interference using a reference signal modulated by Doppler components caused by vibrations in the structure of the receiving equipment carrier during its flight respect to the reference radionavigation system station.

При этом дисперсия ошибки фильтрации частоты при воздействии внешней шумовой помехи определена как

где

- динамическая ошибка фильтрации частоты;

- флуктуационная ошибка фильтрации частоты при воздействии внешней шумовой помехи; K_н2 - коэффициент усиления непрерывной системы фильтрации;

- дисперсия шума эквивалентных наблюдений;

- эквивалентное отношение сигнал/шум; - отношение мощности сигнала к спектральной мощности шума в полосе 1 Гц; ρ(ε_τ) - корреляционная функция дальномерного кода; Δƒ_ССЧ - шумовая полоса пропускания.The noise immunity of tracking systems is characterized by the probability of failure of tracking for a given time. The probability that the absolute value of the instantaneous tracking error will be greater than the specified values [1] is equal to:

In this case, the variance of the frequency filtering error when exposed to external noise interference is defined as

Where

- dynamic frequency filtering error;

- fluctuation error of frequency filtering when exposed to external noise interference; K _n2 is the gain of the continuous filtration system;

- noise variance of equivalent observations;

- equivalent signal to noise ratio; - the ratio of signal power to spectral noise power in the band of 1 Hz; ρ (ε _τ ) is the correlation function of the rangefinder code; Δƒ _SCN - noise bandwidth.

The essence of the utility model is illustrated by the drawing, where in FIG. 1 is a structural diagram of a device for tracking the frequency of a signal of a reference station of a radio navigation system and the following notation is introduced:

1, 2, 3, 4, 5, 6, 7, 8 - mixers;

9 - controlled frequency generator;

10 - code generator;

11, 12 - integrators;

13, 14 - delay blocks;

15 - adder;

16 - smoothing filter;

17, 18, 19, 20 - the outputs of the device.

The signal frequency tracking device of the reference station of the radio navigation system comprises first 1, second 2, third 3, fourth 4, fifth 5, sixth 6, seventh 7 and eighth 8 mixers; controlled frequency generator 9; code generator 10; first 11 and second 12 integrators; first 13 and second 14 delay units; an adder 15; smoothing filter 16; first 17, second 18, third 19, fourth 20 device outputs.

In this case, the first inputs of the first 1 and second 2 mixers are connected to the second 18 output of the device, and their outputs are to the first inputs of the third 3 and fourth 4 mixers, respectively, the second inputs of which are connected to the output of the code generator 10, the input of which is connected to the first output 17 of the device , and their outputs - to the inputs of the first 11 and second 12 integrators, respectively. The output of the first integrator 11 is connected to the second input of the sixth 6 mixer and the input of the first 13 delay unit, the output of which is connected to the first input of the fifth 5 mixer. The output of the second 12 integrator is connected to the second input of the fifth 5 mixer and the input of the second 14 delay unit, the output of which is connected to the first input of the sixth 6 mixer. The outputs of the fifth 5 and sixth 6 mixers are connected respectively to the first and second inputs of the adder 15, the output of which is connected to the input of the smoothing filter 16, the output of which is connected to the second control input of the controlled frequency generator 9, the first input of which is connected to the third 19 device output, and the first and second outputs - with second inputs of the seventh 7 and eighth 8 mixers, respectively, the first inputs of which are connected to the fourth 20 output of the device, and the outputs are respectively with the second inputs, respectively, of the first 1 and second 2 mixers.

A device for tracking the frequency of the signal of the reference station of the radio navigation system operates as follows.

The second output 18 of the device receives transferred to the intermediate frequency and digitized mixture of the navigation signal of the LRNS reference station and noise interference, the level of which has been previously reduced using devices that implement the known methods for increasing the noise immunity of navigation receivers, but it is sufficient to degrade the performance of the device. From the second output 18, the signal is supplied to the first inputs of the first 1 and second 2 mixers.

The fourth output 20 of the device receives a signal containing the Doppler components of the spectrum of dynamic disturbances of the consumer equipment carrier (AP) arising during the flight [2]. This signal is received from the sensors of the inertial navigation system of the carrier’s navigation complex, digitized, filtered and stored in the storage device AP. The signal from the fourth 20 output of the device is supplied to the first inputs of the seventh 7 and eighth 8 mixers.

The first 17 and third 19 outputs of the device receive control signals, respectively, of the code generator 10 and the controlled frequency generator 9, obtained from an external device for searching for a signal by range and frequency.

As a result of multiplication in the seventh 7 and eighth 8 mixers of the Doppler signal of carrier vibrations and harmonic signals from the outputs of the controlled frequency generator 9, the frequency values of which are set by the control signals from the output of the smoothing filter 16 and from the third 19 output of the device, at the outputs of the seventh 7 and eighth 8 mixers receive reference frequency signals shifted relative to each other in phase by π / 2 and modulated by Doppler signals of vibration of the carrier of the AP.

Modulation allows increasing the degree of similarity of the reference signal received by the carrier of the reference station and its current replica, which as a result of further correlation processing leads to an additional decrease in the noise interference level at the outputs of the mixers and an increase in the steepness of the cross-correlation functions at the outputs of the integrators in the in-phase and quadrature channels.

In this case, the modulated reference frequency signals are fed to the second inputs of the first 1 and second 2 mixers, where they are multiplied with the received mixture of the navigation signal and interference, thereby transferring the in-phase and quadrature components of this mixture to zero frequency. Then the signals of these components are fed to the first inputs of the third 3 and fourth 4 mixers, respectively, where they are multiplied with a rangefinder code with a nominal (Promt) delay value supplied to the second inputs of the mixers from the output of the code generator 10, which is controlled by the signal from the first 17 output of the device. The signals from the outputs of the third 3 and fourth 4 mixers are accumulated in the first 11 and second 12 integrators, respectively, the signals from the outputs of which are fed to the corresponding inputs of the discriminating function block, consisting of the first 13, second 14 delay units, fifth 5 and sixth 6 mixers, and also adder 15. The discriminating function block implements the algorithm I _p (k) Q _p (k-1) -I _p (k-1) Q _p (k) and generates at the output of adder 15 a signal proportional to the mismatch between the frequencies of the received navigation signal and his reference copy. The error signal through the smoothing filter 16, as a rule, of the second order of astatism, is fed to the second control input of the controlled frequency generator 9.

Thus, as a result of increasing the signal-to-noise ratio at the correlator output, the frequency filtering error D _ω decreases under the influence of noise interference due to a decrease in the fluctuation component. The probability of failure to monitor the frequency decreases, thereby increasing the noise immunity of the device.

Information sources

1. GLONASS. The principles of construction and operation / Ed. A.I. Perova, V.N. Harisova. Ed. 4th, rev. and add. - M .: Radio engineering, 2010, p. 338, 511. - ISBN 978-5-88070-251-0;

2. Slyusar N.M. Secondary modulation of radar signals by dynamic objects / N.M. Slusar. - Smolensk: VA VPVO Armed Forces of the Russian Federation, 2006. - 173 p.

Claims (1)

A signal frequency tracking device for a reference station of a radio navigation system, comprising first and third mixers connected in series, a first integrator, a first delay unit and a fifth mixer; the second and fourth mixers connected in series, the second integrator, the second delay unit and the sixth mixer; serially connected adder, smoothing filter, controlled frequency generator; code generator; the first, second and third outputs of the device, with the first inputs of the first and second mixers connected to the second output of the device, the first inputs of a controlled frequency generator and code generator connected respectively to the third and first outputs of the device, the output of the code generator connected to the second inputs of the third and fourth mixers, the outputs of the first and second integrators are connected to the second inputs of the sixth and fifth mixers, respectively, the outputs of which are connected respectively to the second and first inputs of the adder, from characterized in that the seventh and eighth mixers and the fourth output of the device, which is connected to the first inputs of the seventh and eighth mixers, the second inputs of which are connected to the outputs of the controlled frequency generator and the outputs to the second inputs of the first and second mixers, are additionally introduced into the device.

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