Gnss signal processor
AssigneeQUALCOMM Incorporated
InventorPhilip John Young
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Abstract
A signal processor for GPS or other GNSS radiolocalization systems, includes a RAM pre-correlation buffer which is filled in sync with the code NCO, thus all sample alignment in the buffer is fixed The device further includes an amplitude compressor to limit the size of the buffer memory and is optimized to provide data to the following DFT unit in small bursts that can be processed in real time without the need for intermediate buffers. Thanks to these features the processor limits the amount of fast intermediate memories, is simpler and has lowerpower consumption.
Claims17
A signal processor for a GNSS digital signal comprising spread-spectrum radiolocalization signals, received from radiolocalization satellites, each satellite transmitting a radiolocalization signal modulated by a known PRN code, having a Doppler shift and a code phase shift, the signal processor comprising:
- at least one sampling stage (35) comprising accumulation means driven by a programmable oscillator (350), for generating a number of samples of programmable duration, determined by the output of the programmable oscillator (350), which is settable according to the Doppler shift of a satellite whose acquisition is intended, and one pre-correlation buffer memory (37), arranged to store the succession of samples produced by the sampling stage,
- at least one correlator engine, arranged to correlate the samples in the pre-correlation buffer with a plurality of local replicas of the PRN codes, each replica having a phase shift, and to generate a plurality of correlation values.
The signal processor of any of the previous claims, further comprising at least one carrier wipeoff unit (325, 322), to remove a carrier component from said GNSS signal and provide a carrier-stripped GNSS signal, wherein the sampling stage is sensitive to the carrier-stripped GNSS signal,
The signal processor of the previous claim, further comprising a compression unit (36), acting on the sampled signals for reducing their dynamic range according to a linear or non-linear compression function.
The signal processor of any of the previous claims, further comprising a biasing unit 33, operatively arranged to encode the values stored in the pre-correlation buffer in a digital number that is always non-negative or always non-positive.
The signal processor of any of the previous claims, comprising at least one code generator (39) generating the local replicas of the PRN codes, wherein said code generator (39) is arranged to introduce a phase-shift in the code at the end of each code period.
The signal processor of any of the previous claims, further comprising a DFT engine (60) connected on output of the correlation engine, arranged to produce multiple correlation taps arranged on several Doppler shifts lines.
A processing method for a GNSS radiolocalization signal comprising the steps of:
- generating or receiving a carrier-stripped GNSS signal comprising spread-spectrum radiolocalization signals, received from radiolocalization satellites, each satellite transmitting a radiolocalization signal modulated by a known PRN code, having a Doppler shift and a code phase shift,
- sampling the carrier-stripped GNSS signal according to a programmable oscillator, which is programmed according to the Doppler shift of a satellite whose acquisition is intended, and storing the samples so obtained in a one pre-correlation buffer memory,
- correlating the samples in the pre-correlation buffer with a plurality of local replicas of the PRN code, each replica having a phase shift, and to generate a plurality of correlation values.
The processing method of any of claims form 10 to 11, further comprising a step of encoding the values stored in the pre-correlation buffer in a digital number that is always non-negative or always non-positive.
The processing method of any of claims form 10 to 12, further comprising a step of generating local replicas of the PRN codes having a phase-shift in the code at the end of each code period.
The processing method of any of claims form 10 to 13, further comprising a step of applying DFT operations to the correlation values in order to obtain multiple correlation taps arranged on several Doppler shifts lines.
The processing method of the previous claim, further comprising a step of computing amplitude values of the correlation taps, and a step of integrating the amplitude in an incoherent integration memory area (81) after subtraction of a common offset amplitude.
Dependencies are inferred from the claim text.