CN-122017891-A - Loop self-adaptive GNSS multipath resisting method based on multi-correlator output

Abstract

The invention relates to the technical field of satellite navigation receiver signal processing and multipath resistance, and particularly discloses a loop self-adaptive GNSS multipath resistance method based on multi-correlator output. The method comprises the steps of taking code tracking punctual time as a center in a baseband tracking loop, arranging a plurality of pairs of symmetrical code delay positions on two sides of the baseband tracking loop, correlating a received signal with a local pseudo code to obtain multipath symmetrical correlation output and punctual correlation output, constructing a local asymmetry index based on each symmetrical correlation amplitude, forming a normalized multipath characteristic index M according to a weighted norm, and optionally combining information such as correlation function slope difference, main lobe/side lobe energy ratio and the like to generate a comprehensive multipath characteristic index for representing the multipath interference degree of a current signal. The receiver adaptively selects a code tracking loop working mode according to the relation between the multipath characteristic index and a preset threshold value, and jointly adjusts the Early-Lat correlator interval and the loop bandwidth.

Inventors

• MENG XIANWEI
• ZHU BO
• ZHANG LEI
• Xie Chungong
• JIA LIN
• WANG YINGCHAO
• TANG JIAQI
• ZHANG HAIBIN
• WANG HAODONG
• WANG SIJIAN
• LI TONGQI

Assignees

• 安徽中科宇疆科技有限公司
• 安徽大学

Dates

Publication Date

20260512

Application Date

20260403

Claims (5)

1. 1. A loop self-adaptive GNSS multipath resisting method based on multi-correlator output is characterized by comprising the following steps: s1, for GNSS intermediate frequency or baseband digital signal obtained by down-conversion and analog-to-digital conversion of radio frequency front end, corresponding to local pseudo code phase with zero delay on code delay axis In the center, a plurality of pairs of symmetrical code delay positions are arranged on two sides of the code delay position 、 Wherein 、 Respectively representing the advanced code phase and the delayed code phase, and correlating with the local pseudo code at each delay position to obtain corresponding advanced correlation output Hysteresis dependent output Code phase Corresponding promtt correlator output I.e., on-time correlation output; s2, calculating local asymmetry index of each symmetrical code delay position based on correlation output of each symmetrical code delay position Weighting and combining the local asymmetry indexes to obtain a multipath characteristic index M for representing the asymmetry degree of the correlation function on a code delay axis; and S3, comparing the multipath characteristic index M with a preset threshold value, selecting the working mode of the code tracking loop according to the section where the M is located, and carrying out self-adaptive adjustment on the correlator interval and the loop bandwidth of the code tracking loop so as to realize the suppression of multipath interference.
2. 2. The loop adaptive GNSS multipath resistant method of claim 1, wherein in step S1, the in-phase component I and the quadrature component Q are calculated at each code delay position, and the non-coherent correlation amplitude is obtained by performing corresponding integral and square sum calculation on the in-phase component and the quadrature component, as shown in the formula: , , Wherein, the And Corresponding to the advanced in-phase and quadrature components, And Corresponding to the lag in-phase and quadrature components, And Corresponding to the in-phase and quadrature components of zero delay. And the local asymmetry index And the multipath characteristic index M are based on And And (5) calculating to obtain the product.
3. 3. The loop-adaptive GNSS multipath resisting method according to claim 1, wherein in step S2, the local asymmetry index is used The definition is as follows: Wherein, the And The correlation outputs for the k-th pair of symmetric code delay positions, To prevent the denominator from approaching zero, the multipath feature index M is defined as: Wherein, the For each symmetric code delay position weight, satisfy And is And setting a larger weight for the minimum code delay position close to zero delay to enhance the sensitivity to short delay multipath interference, wherein the multipath characteristic comprehensive index further comprises an additional index based on the slope of a correlation function and side lobe energy, and the additional index is specifically as follows: (1) In the code phase Calculating local slopes of the correlation function at the left and right adjacent code delay positions, and constructing a slope difference normalization index, wherein k=1: (2) Respectively calculating related energy in a preset main lobe delay range and a side lobe delay range And (3) with And constructing a side lobe energy ratio index: (3) The multipath characteristic comprehensive index is based on M, S and Is a linear combination of (a): Wherein, the 、 、 Is a non-negative weight coefficient.
4. 4. The loop-adaptive GNSS multipath resisting method based on multi-correlator output according to claim 1 wherein a first threshold is preset in step S3 And a second threshold value And meet the following According to the multipath characteristic index M or multipath characteristic comprehensive index The size of (a) configures the code tracking loop into one of three modes of operation. In practical application, select Or (b) One of the above-mentioned materials can be used, Providing finer multipath interference characterization but increasing computational complexity. Taking multipath characteristic index M as an example, the following is specific: (1) When (when) When the code tracking loop is in the first working mode, the correlator interval adopts a first preset value The loop bandwidth adopts a first preset value ; (2) When (when) When the code tracking loop is in the second working mode, the correlator interval adopts a second preset value The loop bandwidth adopts a second preset value ; (3) When (when) When the code tracking loop is in the third working mode, the correlator interval adopts a third preset value The loop bandwidth adopts a third preset value ; Wherein the correlator interval satisfies The loop bandwidth satisfies 。
5. 5. A multipath interference suppressing device for a satellite navigation receiver for implementing a loop-adaptive GNSS multipath resistant method based on multi-correlator output as claimed in any of claims 1 to 4, comprising: (1) A multi-correlator unit (310) for setting a plurality of pairs of symmetrical code delay positions on a code delay axis by taking a zero delay code phase as a center, and correlating with a local pseudo code at each code delay position to obtain a corresponding correlation output and an on-time correlation output; (2) A multipath feature extraction unit (320) for calculating local asymmetry indexes based on the correlation output of the delay positions of the symmetric codes, and weighting and combining the local asymmetry indexes to obtain a multipath feature index M or a multipath feature comprehensive index representing the asymmetry degree of the correlation function on the code delay axis ; (3) A loop control unit (330) for controlling Or (b) Comparing with a preset threshold value according to multipath characteristic index or Or (b) The section selects the working mode of the code tracking loop, and adaptively adjusts the correlator interval and the loop bandwidth of the code tracking loop.

Description

Loop self-adaptive GNSS multipath resisting method based on multi-correlator output Technical Field The invention relates to the field of satellite navigation signal processing, in particular to a loop self-adaptive GNSS multipath resisting method based on multi-correlator output. Background Global satellite navigation systems (GNSS), such as GPS, beidou, GLONASS, galileo, etc., are widely used in the fields of mapping, transportation, unmanned systems, precision time service, etc. The GNSS receiver obtains the code delay and carrier phase of the satellite signals through correlation processing, and further forms pseudo-range and carrier phase observation values for calculating the position, speed and time of the user. In practical application environments, especially urban canyons, under bridges and complex reflection scenes, satellite signals can be reflected or scattered by objects such as buildings, ground, water surfaces and the like in the propagation process to form multipath signals different from direct signal paths, namely multipath signals. After the multipath signal and the direct signal are overlapped at the front end of the receiver, the amplitude and the shape of the correlation function are distorted, so that the locking point of a code tracking loop (such as a Delay Locked Loop (DLL)) is offset, a pseudo-range measurement deviation is formed, and the navigation resolving precision is further affected. The GNSS system adopts a direct sequence spread spectrum technology, and has good inhibition capability on multipath signal interference with larger multipath delay. However, when the multipath delay is small, such as less than 1 chip, it is difficult to obtain satisfactory performance after the conventional direct sequence spread spectrum communication anti-multipath technology is applied to the GNSS system. This is because conventional direct sequence spread spectrum anti-multipath techniques treat such small delay signals as part of a useful signal without processing, such as Rake reception techniques. Thus, such multipath signals will still cause a significant distortion of the pseudorange measurements from the carrier phase measurements. In order to improve the positioning accuracy of the GNSS receiver and reduce the influence of multipath interference, researchers at home and abroad do a great deal of work in four links of satellite signal design, receiver antenna design and site selection, digital signal processing and positioning navigation calculation. The invention mainly focuses on the multipath resisting method of the baseband processing level of the receiver, and the method can be roughly divided into: (1) The correlator structure improvement method is that, for example, the narrow correlator technology improves the multipath resistance by compressing the chip interval, and the Double-Delta technology builds the phase discrimination function through two pairs of correlators and improves the resolution capability of local shape change of the correlation function. The method reduces the code tracking error caused by multipath to a certain extent, but generally has the problems of more sensitivity to noise, fixed parameters, difficult self-adaptive optimization aiming at environmental change and the like. (2) A delay locking method based on multipath parameter estimation is characterized in that a receiving correlation function is modeled as superposition of a direct component and a plurality of multipath components, and the amplitude and delay of each component are estimated through least square or maximum likelihood, so that the real delay of the direct component is extracted. Typical methods include multipath parameter estimation delay locked loops, etc. The method can obtain better multipath inhibition performance in theory, but often needs more correlator sampling points, has higher calculation complexity and is difficult to popularize in a receiver with limited resources or low cost. (3) Signal Quality Monitoring (SQM) and observations weighted class method: The signal quality index is constructed by extracting a plurality of geometric or statistical characteristics on the correlation function and is used for detecting multipath or distorted signals, and then the affected observed values are subjected to weight reduction or rejection during position calculation. The method generally works at the observance and solution level, and can not directly improve the locking performance of the code tracking loop under the multipath condition. Therefore, it is necessary to provide a method and apparatus for extracting multipath characteristics from the output of a correlator and adaptively adjusting the code tracking loop parameters according to the multipath characteristics, so as to improve the multipath resistance of a GNSS receiver in various environments. Disclosure of Invention The invention aims to provide a multipath interference suppression method and device for a GNSS receiver,