US 5,663,734 A · GPS receiver and method for processing GPS signals

Abstract

A GPS receiver in one embodiment includes an antenna which receives GPS signals at an RF frequency from in view satellites; a downconverter coupled to the antenna for reducing the RF frequency of the received GPS signals to an intermediate frequency (IF); a digitizer coupled to the downconverter and sampling the IF GPS signals at a predetermined rate to produce sampled IF GPS signals; a memory coupled to the digitizer storing the sampled IF GPS signals (a snapshot of GPS signals); and a digital signal processor (DSP) coupled to the memory and operating under stored instructions thereby performing Fast Fourier Transform (FFT) operations on the sampled IF GPS signals to provide pseudorange information. These operations typically also include preprocessing and post processing of the GPS signals. After a snapshot of data is taken, the receiver front end is powered down. The GPS receiver in one embodiment also includes other power management features and includes, in another embodiment the capability to correct for errors in its local oscillator which is used to sample the GPS signals. The calculation speed of pseudoranges, and sensitivity of operation, is enhanced by the transmission of the Doppler frequency shifts of in view satellites to the receiver from an external source, such as a basestation in one embodiment of the invention.

Claims60

Dependent claims

A GPS receiver apparatus, comprising:

an antenna for receiving GPS signals at an RF frequency from in view satellites;
a downconverter coupled to said antenna, said downconverter reducing the RF frequency of said received GPS signals to an intermediate frequency (IF);
a digitizer coupled to said downconverter and receiving said IF GPS signals, said digitizer sampling said IF GPS signals at a predetermined rate to produce sampled IF GPS signals;
a memory coupled to said digitizer, said memory storing the sampled IF GPS signals;
and
a digital signal processor (DSP) coupled to said memory, said DSP performing fast convolution, wherein said digital signal processor processes said sampled IF GPS signals by performing a plurality of fast convolutions on a corresponding plurality of blocks of said sampled IF GPS signals to provide a plurality of corresponding results of each fast convolution and summing a plurality of mathematical representations of said plurality of corresponding results to obtain a first position information.

3 more elements

A method of determining pseudoranges in a global positioning satellite (GPS) receiver, comprising:

receiving GPS signals from one or more in view GPS satellites utilizing an antenna coupled to a downconverter, said GPS signals comprising pseudorandom sequences;
buffering the received GPS signals in a digital snapshot memory;
processing the buffered GPS signals for one or more of the in view GPS satellites in a digital signal processor by:
breaking the buffered data into a series of contiguous blocks whose durations are equal to a multiple of the frame period of the pseudorandom (PN) codes contained within the GPS signals,
for each block, creating a compressed block of data with length equal to the duration of a pseudorandom code period by adding together successive subblocks of data, said subblocks having duration equal to one PN frame, such that the corresponding sample numbers of each of the subblocks are added to one another;
for each compressed block, performing a convolution of the compressed block's data against the pseudorandom sequence (PRS) of the GPS satellite being processed, said convolution being performed using fast convolution algorithms, said convolution producing a result;
performing a magnitude-squared operation on the results created from each of said convolutions to produce magnitude-squared data;
combining said magnitude-squared data for all blocks into a single block of data by adding together such blocks of magnitude-squared data, such that the corresponding sample numbers of each of the magnitude-squares from the convolution are added to one another;
and
finding the location of the peak of said single block of data to high precision using digital interpolation methods, where the location is the distance from the beginning of the data block to the said peak, and the location represents a pseudorange to a GPS satellite corresponding to the PRS being processed.

7 more elements

A tracking process utilizing global positioning system (GPS) satellites for determining the position of a remote sensor, the process comprising the steps of:

receiving and storing GPS signals at said remote sensor from a plurality of in view GPS satellites;
computing pseudoranges in the sensor, utilizing said GPS signals, said computing comprising digital signal processing using fast convolution techniques on stored GPS signals;
transmitting said pseudoranges from said sensor to a base station, said base station being provided with GPS satellite ephemeris data;
and
receiving said pseudoranges at said base station and utilizing said pseudoranges and said satellite ephemeris data to compute a geographic location for said sensor, wherein the step of computing the pseudoranges comprises:
storing the received GPS signals in a memory;
processing the stored GPS signals for one or more of the in view GPS satellites in a digital signal processor by:
breaking the stored data into a series of contiguous blocks whose durations are equal to a multiple of the frame period of the pseudorandom (PN) codes contained within the GPS signals;
for each block, creating a compressed block of data with length equal to the duration of a pseudorandom code period by coherently adding together successive subblocks of data, said subblocks having duration equal to one PN frame;
for each compressed block, performing a matched filtering operation to determine the relative timing between the received PN code contained within the block of data and a locally generated PN reference signal, said matched filtering operation utilizing said fast convolution techniques;
and
determining said pseudorange by performing a magnitude-squared operation on the products created from said matched filtering operation and combining said magnitude-squared data for all blocks into a single block of data by adding together said blocks of magnitude-squared data to produce a peak, the location of said peak being determined using digital interpolation methods and corresponding to said pseudorange.

9 more elements

A process utilizing global positioning system (GPS) satellites for determining the position of a remote sensor, the process comprising the steps of:

receiving and storing GPS signals at said remote sensor from a plurality of in view GPS satellites;
computing pseudoranges in the sensor, utilizing said GPS signals, said computing comprising digital signal processing using fast convolution techniques on stored GPS signals;
receiving a transmission of satellite data information comprising data representative of ephemeris for a plurality of satellites;
computing position information in the sensor by using said satellite data information and said pseudoranges, wherein the step of computing the pseudoranges comprises:
storing the received GPS signals in a memory;
processing the stored GPS signals for one or more of the in view GPS satellites in a digital signal processor by:
breaking the stored data into a series of contiguous blocks whose durations are equal to a multiple of the frame period of the pseudorandom (PN) codes contained within the GPS signals;
for each block, creating a compressed block of data with length equal to the duration of a pseudorandom code period by coherently adding together successive subblocks of data, said subblocks having duration equal to one PN frame;
for each compressed block, performing a matched filtering operation to determine the relative timing between the received PN code contained within the block of data and a locally generated PN reference signal, said matched filtering operation utilizing said fast convolution techniques;
and
determining said pseudorange by performing a magnitude-squared operation on the products created from said matched filtering operation and combining said magnitude-squared data for all blocks into a single block of data by adding together said blocks of magnitude-squared data to produce a peak, the location of said peak being determined using digital interpolation me and corresponding to said pseudorange.

8 more elements

Dependencies are inferred from the claim text.

GPS receiver and method for processing GPS signals

Life of this patent

GPS receiver and method for processing GPS signals

Life of this patent

Abstract

Claims60