UA53604A - Method for eliminating errors caused by the effect of several signal beams when receiving signals in a satellite navigation system - Google Patents

Abstract

The proposed method for eliminating errors caused by the effect of several signal beams when receiving signals in a satellite navigation system consists in performing operations of detecting a signal of the navigation satellite from the carrier frequency and reception delay of the coded signal, tracking the detected signal, measuring the radionavigation parameters and amplitude of the signal, providing bit synchronization of the signal, and isolating overhead information transmitted by the satellite. Then consequently the following operations are performed: smoothing the signal amplitude values, smoothing the distance data, determining the deviations of the signal amplitude values from the average amplitude, determining the deviations of the distance values from the average distance, determining the covariation function as the product of the amplitude and distance deviations, providing the primary smoothing of the covariation function, determining the availability of several signal beams by comparing the covariation function with threshold values, providing the secondary smoothing of the covariation function, determining a measurement error, and inserting corrections for the distance values obtained by measuring the reception delay of the coded signal and the phase difference of the direct and reflected signals. To determine signal phase differences and errors, and smoothing the covariation function, specified equations are used.

Description

Description of the invention

The invention relates to the field of radio engineering, and in particular, radio navigation using the signals of 2 navigation satellite systems ORZ and GLONASS.

The proposed method can be used to suppress multipath errors in satellite navigation receivers, which simultaneously receive and parallelly process signals from ORZ and GLONASS satellite navigation systems.

The antenna of the satellite navigation receiver receives both a direct satellite signal and a signal reflected from 70 surrounding objects and objects; in other words, real satellite receivers operate under conditions of multipath signal propagation. The delay of the reflected signal relative to the direct one distorts the leading edge of the cross-correlation function (CRF) of the received and expected signal and leads to range measurement errors (wide position of the CRF peak on the time axis). The sign of this error changes depending on the difference in the phases of the direct and reflected signals (reflected in phase with the direct or in antiphase), and the value is usually 72 units of meters (for modern receivers with a narrow-gate correlator and an extended frequency band of the radio path). Sometimes this error can reach 10-15 meters. Multipath errors become independent in two antennas when they are spaced even by fractions of a wavelength. This circumstance limits the accuracy of the differential mode to the level of the above-mentioned values, even if there are no multibeam errors in the reference station, or if they are eliminated by some complication of the equipment of this station, or by the measurement processing algorithm. These errors are always present in the case of a consumer who is in more difficult conditions in terms of the possibility of mirroring signals and who uses ordinary receivers. This limitation prompted the developers of receiving equipment to look for simple and effective ways to suppress multipath errors in the receiver itself. Quite a lot of such methods are currently known (every developer company widely advertises its own), but not all of them provide a sub-meter level of accuracy, and if they do, it is at the cost of significant complication and travel of the receivers. "

Analogues of the proposed method are known, based on the analysis of variations in the amplitude of the received multi-beam signal to suppress rangefinder errors |11, (21.

A known method of suppressing multipath errors is based on the analysis through the so-called "vigepdiy ragategseg X" - addition of the power of the reflected signal to the power of the direct |11. WITH

However, this method is very complex in terms of hardware and requires significant resource-intensive software implementation. "3

First, it requires a bank of correlators with different delays of reference signals (MES - Mikurai

Ezvytavdipa YuOeiau GoskK Goor - observation circuit for estimating the delay of a multi-beam signal). eh

Secondly, the outputs of these correlators are summed with weights, which require cumbersome complex calculations (with the use of double summation) and compensate for the shifts of the VKF peak caused by multiradiation.

Compensation is achieved by reverse shift of the zero-crossing point of the discrimination characteristic of the tracking rangefinder.

The closest analogue (prototype) of the proposed method is the method of suppressing multipath errors, in which the output is the signal-to-noise ratio (SNR), expressed in AM units (Tgitbrie "

Atriyshide Opiev), from which the signal/noise amplitude ratio (SNR) |21 is formed and processed. With 50 ZMAA, according to |2| complete spectral analysis is performed in two stages - initialization and refinement due to the two-time application of AME (Adariime Moi Rieg) and A! 5 (Adariimme iIeavi bdptsage), i.e

From" the adaptive Norse filter (AME) and the method of least squares (AG 5). Estimates of the amplitudes, frequencies, and initial phases of the reflected signals obtained in this way are used to calculate the phase errors of the carrier code.

This method does not use a strong mutual correlation (the coefficient of this correlation is close to the i-th unit) between ZMKA and measurement errors, but uses the known functional dependence between the parameters of the reflected signal and range and carrier phase errors. Estimates of the indicated errors of the radio navigation parameters are calculated using the estimates of the parameters of the reflected signal, obtained from the analysis of amplitudes b (ZMKA). This method is closest to the proposed one based on the above strong mutual av! 20 correlations. As in the proposed method, here, in addition to the standard operations performed by any navigation receiver, namely:

T" n - search for signals of navigation satellites by carrier frequency and code delay; n- monitoring of the signals of the found satellites by circuits that monitor the carrier and delay; n- measurement (estimation) of radio navigation parameters; 29 "« bit synchronization and selection of service information transmitted by satellites; in. " measurement, smoothing and analysis of the amplitude of the received signal is also carried out.

Disadvantages of the prototype: "- delays in the 5MKA filters, which do not allow to form corrections to measurements in real time (at the rate of coordinate recovery), which significantly limits the scope of applications of this method; 60 "- the insufficient probability of the obtained results, since for the calculation of corrections to measurements of radio navigation parameters, information from only one indirect source is used - amplitude variations (false corrections to measurements may be made due to the influence on the amplitude of other types of interference); " the complexity and resource-intensive computing operations, which limit its use in mass consumer equipment.

The invention is based on the problem of eliminating the shortcomings of the prototype, which is weighed by the fact that in the proposed method of suppressing multipath errors, which includes the operations of searching for signals of navigation satellites by carrier frequency and code delay, accompanying the found signals with tracking loops, by carrier and delay, measuring radio navigation parameters, as well as the amplitude of the received signals, bit synchronization and selection of the service information transmitted by the satellite, variations (deviations from the smoothed trend) of range and amplitude measurements are formed, the second mixed moment of the range and amplitude connection (their covariance) is calculated.

The technical result of the proposed invention is achieved by the fact that in the method of suppressing multipath errors 70 in satellite navigation receivers, operations of amplitude smoothing, range smoothing, formation of amplitude variations, formation of range variations, formation of covariance as a product of amplitude and range variations, primary smoothing of covariations, detection (detection) of the fact of the influence of multipath (comparison with the threshold), decision-making (upon exceeding the threshold), secondary covariance smoothing, calculation of the range error estimate by dividing the mentioned covariance by the current /5 value of the amplitude variation and introducing corrections to the code and phase ranges, calculating the difference phases of direct and reflected signals, calculation of the estimation of the error of the current phase caused by multipath and the introduction of corrections into the measurements of the current phase.

The set of listed features allows you to increase the probability of the obtained results, to simplify computational operations that limit the use of algorithms in mass consumer equipment.

In the method, variations (deviations from the smoothed trend) of range and amplitude measurements are additionally formed, and the second mixed moment of the relationship between range and amplitude (their covariance) is calculated.

The covariation is additionally smoothed at an interval of 30-bO0s (multi-beam interference period). The current estimate of the multibeam range error is calculated by dividing the current covariance estimate by the current deviation of the amplitude from its mean value.

The covariance is smoothed using a recurrent linear procedure of the 1st order (a filter with an infinite impulse response and an attenuation parameter a, which will be referred to as the a-BIR filter in the following):

Ha-yuKhytah, a) , " from where y is an updated estimate of the quantity that is being smoothed;

And | "c) x47 preliminary assessment; with

X; - sampling element of the smoothing parameter; co

A is the smoothing coefficient.

If X is a covariance, that is, the product of variations (deviations from the current average values of the amplitude b5A,;, and the range 50), then it is desirable to choose the parameter "A" in the range of 0.015-0.03.

The same procedure is performed to calculate the average value of the amplitude. Range variations are calculated as deviations of current measurements from the smoothed trend. The range trend is obtained by smoothing « 20 code ranges with high-precision phase measurements (Doppler integrals) according to the formula: z с - 1 ві i (2) h Бі - УХО-У ДО) UDO іт пі 1 1

About; and and - the measured and smoothed value of the code range, respectively; sl

Di; - Doppler integral (carrier phase attack) in the interval from u.4 to u. (95) The resulting amplitude and range variations are additionally smoothed by the recurrent formula (1) with the coefficient

Fu (in the range of 0.1-0.3).

To increase the reliability and probability of suppression of multibeam errors, a preliminary (av) operation of their detection is introduced.

T» The multibeam detector is the result of comparing the mentioned covariance, smoothed from A-01, with the previously established threshold C. The threshold value is determined through the acceptable residual level of multibeam errors in accordance with the theory of statistical hypothesis testing by the maximum likelihood criterion and is specified experimentally. The ratio between the current phase in; of the vector reflected from the signal and -it (3) n ----

T

60th - current moment of time; ия - the moment of the nearest previous maximum of the amplitude; schi - phase difference of direct and reflected signals;

T - the period of amplitude fluctuations caused by multibeam interference and the current error 65 of the AF phase meter; represented by a vector diagram.

In fig. a vector diagram is shown, where a is a direct signal vector;

b is the vector of the reflected signal.

From the known formulas for the connection of the elements of an oblique-angled triangle, we obtain:

AND

In usovtsi -

Addendum: VGOSOYE penalty

Am I the 2nd sobu 70 de

AT; - current error of the phase meter; the ratio of the amplitudes of the reflected and direct signals is indicated by Г; schi - the phase difference of direct and reflected signals. The amplitude of the direct signal is a smoothed average value.

The amplitude of the reflected signal is the half-difference of its maximum and minimum deviation from the average.

Sources of information: 1. SadaTsany EE! - Bowey A., Mei; Raspieg apa biezhaga I. Oe miiiYbizv. "Oevidp oyi SOR Keseimeg Sode apa

Satieg TgaskKkipu I oorz Tog Miiraii Mibdaiop" Rgos oi IOM-98 1041-1053. 2. SPgivyurpeg M. Sotr apa Repippa Aheigad. Ap adarime ZMK -razei sagpieg rpase tiyiraii tibdaiop

Iespidtse". Rgos OGIOM SRBZ-96, pp. 683-696.

Claims (2)

The formula of the invention 1. The method of suppressing multipath errors in satellite navigation receivers, which consists in performing the operations of searching for signals of navigation satellites by carrier frequency and code delay, accompanying the found signals with tracking loops on the carrier and delay, measuring radio navigation parameters, as well as the amplitude of the received signal, bit synchronization and selection of the service information transmitted by the satellite, which is distinguished by the fact that the operations of amplitude smoothing, range smoothing, formation of amplitude variations, formation of range variations, formation of covariation "g zo" as the product of amplitude and range variations, primary covariance smoothing, detection (detection) of the fact of the influence of multibeam (comparison with the threshold), decision-making (upon exceeding the threshold), secondary smoothing of covariances, calculation of the range error estimate by dividing the mentioned covariance by the current "so value of the amplitude variation and entering corrections to code and phase ranges, calculation of the phase difference of direct and reflected signals, calculation of the estimate of the current phase error caused by multiradiation and the introduction of 5 Corrections to measurements of the current phase, and calculation of the phase difference of direct and reflected signals (current and phase angle determined by the formula: where is the current phase angle; ! - s -- CURRENT moment of time; h» 1, - the moment of the amplitude closest to the current previous maximum; n T is the period of amplitude fluctuations caused by multibeam interference (the interval between adjacent maxima, which contains ,; ), and the estimate of the error of the current phase caused by multibeam is calculated by the formula v (o) da va; 20 By o where through the indicated ratio of the amplitudes of the reflected and direct signals; c» Ar - the current error of the phase meter; i - the phase difference of the direct and reflected signals, M, as the amplitude of the direct signal, its current smoothed value is taken, as the amplitude of the reflected signal, the half difference of the maximum and minimum values of the amplitude closest to the current moment of time /; . 2. The method according to claim 1, which differs in that the smoothing of amplitude and covariance readings is performed by any of the methods known in mathematical statistics, for example by the formula: Gor de X - updated estimate of the value being smoothed; and 65 X / 7 preliminary assessment; 1-1 d, - the sampling element of the smoothing parameter; And "its" is the smoothing coefficient. Q. The method according to claims 1, 2, which differs in that the smoothing of the measured range values p and is carried out recurrently using information about the measured values of the Doppler integrals DY;, for example, according to the formula: where p is the updated estimate of the smoothed range when the next measurement is received ; 1 B, - the same assessment at the previous step; "it is the smoothing coefficient; - again the measured range value. r., in the city of Dd Fig. Official bulletin "Industrial Property". Book 1 "Inventions, useful models, topographies of integrated microcircuits", 2003, M 1, 15.01.2003. State Department of Intellectual Property of the Ministry of Education and Science of Ukraine. « « Zo o (Se) (ze) IS c) - with . and? 1 (95) (o) Ge Sho p» 60 b5