Method of reducing inter-channel biases in glonass gnss receivers

Abstract

The present invention discloses methods of accuracy improving for code measurements in GLONASS GNSS receivers. One component of error budget in code measurements of GLONASS receivers is caused by a difference in signal delays arising in the receiver analog Front End and antenna filter on different channel frequencies specific to GLONASS satellites. Methods to compensate for differences in delays for different GLONASS channel frequencies have been proposed using data collected from a GLONASS signals simulator.

What is claimed is: 
     
         1 . A method of reducing inter-channel bias in a GLONASS receiver, the method comprising:
 for each satellite channel, storing correction data for different temperature in a memory;   measuring a current temperature of an analog Front-End of the GLONASS receiver;   receiving signals from GLONASS satellites and determining the primary code measurements for each GLONASS satellite;   applying the correction data from the memory to the determined primary code measurements to compensate for temperature-dependent inter-channel biases in the primary code measurements using the measured current temperature; and   outputting the corrected primary code measurements.   
     
     
         2 . The method of  claim 1 , wherein the memory is a local memory of the GLONASS receiver. 
     
     
         3 . The method of  claim 2 , wherein the correction data is downloaded into the memory from an external source. 
     
     
         4 . The method of  claim 1 , wherein the memory is located remotely from the GLONASS receiver and the applying step is performed remotely from the GLONASS receiver. 
     
     
         5 . The method of  claim 1 , further comprising calculating current coordinates based on the corrected primary code measurements. 
     
     
         6 . The method of  claim 1 , further comprising obtaining the correction data for different temperatures of the analog Front-End placed in a thermal chamber and using a GLONASS simulator, and taking into account a delay of the signals from GLONASS satellites in the analog Front-End and an antenna filter. 
     
     
         7 . The method of  claim 6 , wherein a set of temperatures in the thermal chamber is selected such that the temperature varies in increments of up to 10° C. over a range of temperature changes in the analog Front-End of at least 50° C.; 
     
     
         8 . The method of  claim 7 , wherein the value of a compensation for the inter channel biases for the current reading of the thermal sensor is calculated by linear interpolation, if the analog Front-End temperature is within the range of temperature changes, and by approximation functions if the analog Front-End temperature is outside the range of temperature changes. 
     
     
         9 . The method of  claim 8 , wherein a sum of a constant and harmonic functions parameters of which are determined based on measurements of the correction data, are used as the approximation functions. 
     
     
         10 . The method of  claim 1 , further comprising outputting the current temperature and the determined primary code measurements. 
     
     
         11 . The method of  claim 1 , wherein the determining the primary code measurements step is based on a GLONASS standard-precision signal. 
     
     
         12 . A GLONASS receiver with reduced inter-channel bias comprising:
 an antenna receiving signals from GLONASS satellites;   an analog Front-End receiving and processing the signals from the antenna;   a digital circuit receiving the processed signals from the analog Front-End;   a memory accessible by the digital circuit and storing correction data, including correction data corresponding to signal delay in the Front-End and in an antenna filter of the GLONASS receiver for different temperatures for each satellite channel; and   a temperature sensor measuring a current temperature of the analog Front-End of the GLONASS receiver;   wherein the digital circuit, using the measured current temperature, applies the correction data from the memory to the determined primary code measurements to compensate for temperature-dependent inter-channel biases in the primary code measurements and outputs corrected primary code measurements.   
     
     
         13 . A method of reducing inter-channel bias in a GLONASS receiver, the method comprising:
 generating primary code measurements in the GLONASS receiver, including using a Delay Lock Loop (DLL) for tracking GLONASS signals, where a position of a working discriminator point depends on delays in an analog Front-End of the GLONASS receiver, delays in antenna filters of the GLONASS receiver, and on discriminator characteristic slope;   for each satellite channel, applying inter-channel bias correction data from a memory to the determined primary code measurements to compensate for the inter-channel biases in the primary code measurements; and   outputting the corrected primary code measurements.   
     
     
         14 . The method of  claim 13 , further comprising adding a constant to the output signal of a discriminator of the DLL. 
     
     
         15 . The method of  claim 13 , wherein:
 in a reference strobe sequence used to obtain the discriminator characteristic slope, the position of each strobe being fixed to the boundaries of each GLONASS PRN code chip; and   a sign of each strobe corresponds to a sign of a next PRN code chip;   each strobe of the reference sequence includes a sequence of some positive and some negative elements; and   a number of the positive elements is different from a number of the negative elements,   wherein the sign of each strobe is a sum of the signs of the elements of the strobe.   
     
     
         16 . The method of  claim 15 , wherein a ratio of the positive elements and the negative elements in each strobe is 3:1. 
     
     
         17 . The method of  claim 13 , wherein the memory is a local memory of the GLONASS receiver. 
     
     
         18 . The method of  claim 13 , further comprising calculating current coordinates based on the corrected primary code measurements. 
     
     
         19 . The method of  claim 13 , further comprising obtaining the correction data using a GLONASS simulator, and taking into account a delay of the signals from GLONASS satellites in the analog Front-End and the antenna filters. 
     
     
         20 . A GLONASS receiver with reduced inter-channel bias, comprising:
 an antenna receiving signals from GLONASS satellites;   an analog Front-End receiving and processing the signals from the antenna;   a digital circuit receiving the processed signals from the analog Front-End;   a Delay Lock Loop (DLL) for tracking GLONASS signals, where a position of a working discriminator point depends on delays in an analog Front-End of the GLONASS receiver, delays in antenna filters of the GLONASS receiver, and on discriminator characteristic slope;   a memory accessible by the digital circuit and storing inter-channel bias correction data, including data corresponding to signal delay in the analog Front-End and in the antenna filters for each satellite channel;   the digital circuit generating primary code measurements based on an output of the DLL and applying the correction data to the generated primary code measurements to compensate for the inter-channel biases in the primary code measurements; and   wherein the digital circuit outputs the corrected primary code measurements.   
     
     
         21 . A method of reducing inter-channel bias in a GLONASS receiver, the method comprising:
 generating primary code measurements based on high-precision GLONASS signals;   compensating for inter-channel biases in the primary code measurements using correction data for each satellite channel previously stored in a memory of the GLONASS receiver by adding the corrections to the primary code measurements, and outputting compensated primary code measurements;   wherein the correction data is obtained using a GLONASS simulator and takes into account a delay of the high-precision GLONASS signals in an analog Front-End and antenna filters of the GLONASS receiver.   
     
     
         22 . A GLONASS receiver with reduced inter-channel bias, comprising:
 an antenna receiving signals from GLONASS satellites;   an analog Front-End receiving and processing the signals from the antenna;   a digital circuit receiving, processing and generating primary code measurements based on an output of the analog Front-End;   the digital circuit applying correction data to the generated primary code measurements to compensate for the inter-channel biases in the primary code measurements, and outputting the corrected primary code measurements   a memory accessible by the digital circuit and storing inter-channel bias correction data, including data corresponding to signal delay in the analog Front-End and in the antenna filters for each satellite channel.