# The method of suppression of multipath errors in satellite navigation receivers

The method of suppression of multipath errors in the satellite navigation receiver relates to the field of radio, and in particular navigation using signals of satellite navigation systems GPS and GLONASS. Achievable technical result is the suppression of multipath errors in satellite navigation receivers simultaneously receiving and simultaneously processing the signals of satellite navigation systems GPS and GLONASS. The method of suppression of multipath errors in satellite navigation receivers, which perform a search operation signals of navigation satellites on the carrier frequency and the delay code, support was found signals of servo circuits on the carrier and the delay measurement navigation options, as well as the amplitude of the received signal, the bit synchronization and allocation transmitted by satellite service information, additionally carried out sequentially the operation of smoothing the amplitude smoothing range, the formation of the amplitude variation, the formation of the variation range, the formation of the covariance as works of variations in the amplitude and range of the primary smoothing covariance detection (detection) of fact, d is the covariance, calculate the estimation error range by dividing mentioned covariance on the current value of the variations of the amplitude and the introduction of amendments to the code and phase range, the calculation of the phase difference between the direct and reflected signals, calculation, estimation errors for the current phase, caused by megalocephaly and the introduction of amendments to the measurement of the current phase. 1 C.p. f-crystals, 1 Il.

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

The proposed method can be used to suppress multipath errors in satellite navigation receivers simultaneously receiving and simultaneously processing the signals of satellite navigation systems GPS and GLONASS.

The antenna of the satellite navigation receiver perceives as a direct satellite signal and reflected from the surrounding objects and objects; in other words, the real satellite receivers operate in conditions of multipath propagation of the signals. The delay of the reflected signal relative to the direct distorts the front edge of intercorrelation functions (MCFs) accepted and expected signal and leads to errors of measurement range (itinerating signals (reflected in phase with the direct or inverted), and the value is typically a few meters (for advanced receivers with usastronomy the correlator and extended frequency band radio). Sometimes this error can reach 10-15 meters. Errors multipath become independent in the two antennas when you explode them even at a fraction of a wavelength. This circumstance limits the accuracy of the differential mode at the level of the above values, even if the reference station multipath errors no or they eliminated any complication of the apparatus of this station or processing algorithm measurements. The consumer, in more complex from the point of view of the reflection signal conditions and using conventional receiver, these errors are always present. This limitation has prompted developers to receiving equipment to find simple and effective ways to suppress multipath errors in the receiver. Such methods currently know quite a lot (every company-developer of the widely advertises its own), but not all of them provide submeter accuracy level, and if they allow, then the cost of a significant complexity and cost of receivers.

Known analogues of the proposed method, the basis is, 2].

There is a method of suppressing multipath errors based on the analysis through the so-called "strength parameter X is the additive power of the reflected signal power direct [1].

However, this method is very complicated hardware and resource-intensive software implementations. First, it requires a Bank of correlators with different delays of the reference signals (MEDLL - Multypath Estimading Delay Lock Loop circuit for tracking evaluation delay of multipath signal). Secondly, the outputs of these correlators summed with weights, which require bulky complex calculations (using the double summation) and compensate for bias peak MCFs caused by megalocephaly. Compensation is achieved by the reverse displacement of the point of zero crossing discriminatory characteristic of the witness of the rangefinder.

The closest analogue (prototype) of the proposed method is a method of suppressing multipath errors, in which the source is the signal-to-noise ratio (SNR), expressed in units of AMU (Trimble Amplitude Units), from which it is formed and processed amplitude signal-to-noise ratio (SNRA) [2].

SNRA, in accordance with [2], is full spectral analysis in two stages: initialization and refinement due to the double use of ANF (North Adaptive Filter) of the m estimates of the amplitudes, frequencies and initial phases of the reflected signals are used to calculate the phase error in the code and carrier.

This method does not use a strong mutual correlation (coefficient of this correlation is close to unity) between the SNRA and measurement errors, and uses the well-known functional relationship between the parameters of the reflected signal and the error range, and the phase of the carrier. The estimates of the errors of navigation parameters calculated using estimates of the parameters of the reflected signal received from the amplitude analysis (SNRA). However, this method is most similar to the proposed, based on the above strong mutual correlation. As in the proposed method, here, in addition to the standard operations of any navigation receiver, namely:

- search for signals of navigation satellites on the carrier frequency and the delay code;

- support signals found satellites tracking the contours of the carrier and delay;

- measurement (assessment) radio parameters;

bit synchronization and allocation transmitted by satellites of service information; and

- is measurement, smoothing and analysis of the amplitude of the received signal.

The disadvantages of the prototype:

- saderia coordinates), that significantly limits the scope of application of this method;

- lack of reliability of the obtained results, since to calculate the corrections to the measurements radionavigation parameter is used only one indirect source of variation in the amplitude (may produce false corrections to the measurements due to the impact on the amplitude of the other types of interference);

- the complexity and computational intensity of operations, limiting its use in the apparatus of the mass consumer.

The basis of the invention is to eliminate the disadvantages of the prototype, which is solved in that in the proposed method of suppression of multipath errors, including a search operation signals of navigation satellites on the carrier frequency and the delay code, support was found signals of servo circuits on the carrier and the delay measurement navigation options, as well as the amplitude of the received signals, bit synchronization and allocation transmitted by satellite service information generated variations (deviations from the smoothed trend) measurement range and amplitude, calculates a second mixed moment of communication range and amplitude (covariance).

The technical result is tikovoi navigation additionally carry out the operation of smoothing the amplitude, smoothing range, the formation of the amplitude variation, the formation of the variation range, the formation of the covariance as works of variations in the amplitude and range of the primary smoothing covariance detection (detecting) the fact of the impact of multipath (comparison with a threshold), a decision (on the threshold), the secondary smoothing covariance calculations estimate an error range by dividing mentioned covariance on the current value of the variations of the amplitude and the introduction of amendments to the code and phase range, the calculation of the phase difference between the direct and reflected signals, calculation, estimation errors for the current phase, caused by megalocephaly and the introduction of amendments to the measurement of the current phase.

The combination of these signs can improve the accuracy of the obtained results, to simplify the computational procedure that restricts the use of equipment mass consumer.

The method further form variations (deviations from the smoothed trend) measurement range and amplitude, calculates a second mixed moment of communication range and amplitude (covariance).

The covariance additionally smooth on the interval 30-60 s (period of multipath interference). The current evaluation of water from its average value.

The smooth covariance with linear recurrent procedure 1 order (filter with infinite impulse response and the attenuation parameter, which later will be called-IIR filter):

where_{i}- updated evaluation of the smoothed value;

_{i-1}previous evaluation; and

X_{i}again received by the processing element of the sample to be smoothed parameter;

the smoothing factor.

If X is the covariance, i.e., the product of the variations (deviations from the current average amplitudeAnd_{i}and rangeD_{i}optionit is advisable to choose in the range of 0.015-0.03 in.

The same procedure is performed to compute the average amplitude value. Variations of the distances is calculated as the deviation of the current measurements from the smoothed trend. The trend range is obtained by smoothing code ranges precision phase measurements (Doppler integrals) by the formula

where D_{i-1}the same_{ik-1}to t_{k)}.

The obtained variations of the amplitude and range additionally smooth on recurrence formula (1) with coefficientin the range of 0.1-0.3.

To improve the reliability and validity of the suppression of multipath errors introduced a preliminary operation detecting them.

The multipath detector is the result of the comparison mentioned covariance, smoothed with=0,1 with a pre-established threshold to the threshold Value determined through an allowable residual level of multipath errors in accordance with theory of testing statistical hypotheses on the criterion of maximum prawdopodobnie and clarify experimentally. The ratio between the current phase_{i}vector of the reflected signal

where t_{i}- current time;

t_{m}- the nearest point of the previous maximum amplitude;

_{i}- the phase difference between the direct and reflected signals;

T is the period of oscillation amplitude caused by multipath interference, and the current error of the phase meter_{i}presented vector dia is La.

From the known formulas connection elements oblique triangle ABM is received:

where throughthe indicated ratio of amplitudes of the reflected and direct signals.

The amplitude of the direct signal is its smooth average. The amplitude of the reflected signal polprasert its maximum and minimum deviations from the average.

Sources of information

1. Gadallah El - Sayed A., Meiz Pachter and Steward L. De vilbiss. "Design of GPS Receiver Code and Carrier Tracking Loops for Multipath Mitigation" Proc of ION-98, pp 1041-1053.

2. Christopher Y. Comp and Penina Axelrad. An adaptive SNR - based carrier phase multipath mitigation tecnigue. Proc of ION GPS-96, pp 683-696.

Claims

1. The method of suppression of multipath errors in the satellite navigation receiver that includes a search operation signals of navigation satellites, support was found signals witness outlines, dimension radionavigation parameters ranges, as well as the amplitude of the received signal, characterized in that sequentially carry out the operation of smoothing the amplitude variation range, the formation of the covariance as works of variations in the amplitude and range of the primary smoothing covariance of discovery of the effects of multipath by comparing the UE is ilenia estimation error range by dividing mentioned covariance on the current value of the variations of the amplitude and the introduction of amendments to the measured distance, calculation of the phase difference between the direct and reflected signals - current phase angle_{i}by the formula (1),

where t_{i}- current time;

t_{m}- time nearest to the current previous maximum amplitude;

T is the period of oscillation amplitude caused by multi-beam interference as the interval between two adjacent its maximum capacity of t_{i}calculate the estimation error of the current phase, caused by megalocephaly by the formula (2):

where- the ratio of the amplitudes of the reflected and direct signals;

_{i}- the current phase error;

_{i}- the phase difference between the direct and reflected signals.

2. The method according to p. 1, characterized in that the smoothing counts amplitude and covariances is performed according to the formula (3)

where- updated evaluation of the smoothed value;

previous evaluation; and

X_{i}again received by the processing element of the sample to be smoothed parameter;

the smoothing factor.

**Same patents:**

FIELD: digital cartography and symbolic circuits.

SUBSTANCE: method includes forming matrix for transforming image or objects coordinates distortion matrix on certain digital plans and symbolic circuits relatively to true geographic coordinates received for tracked objects via navigation devices of users, by combining plans or symbolic circuits with precise terrain chart. Distortion matrix is included in contour of displaying objects on plans and circuits, on basis of true geographic coordinates of tracked objects, sent in by users. A layer of plan or circuit of terrain transformed according to matrix is formed, on which tracked objects are marked by certain graphic symbols. Data, received on circuit, for example, route and movement speed of each tracked object, is relayed to certain users with visualization of symbolic circuit on indication device of each user. Device for realization of method has digital terrain chart, received information processing device, information indication device, n components of subscribers complex. Each component has device for determining coordinates on terrain connected by its input to output of controlling device, directly or through encoder/decoder. Outputs of control device are connected to inputs of information indication device and to device for connecting to radio channel. Device for connecting each subscriber component to radio channel is connected by its input to output of control device and is connected to group device for connecting to radio channel belonging to base portion of device for receiving digital cartographic material. Another input and output of group device for connecting to radio channel are connected directly to output and input of coordinates transforming and controlling device or respectively to output and input of second encoder/decoder, connected by other its input and output respectively to output and input of device for coordinates transformation and control. Another input of coordinates transformation and control device is connected to output of distortion matrix storage device. Next input and output of coordinates transformation and control device are connected respectively to output and input of block, containing digital terrain charts and to output and input of block, containing symbolic circuits or plans of same terrain.

EFFECT: higher speed of operation, higher effectiveness.

2 cl, 1 dwg