L1/l2 GPS receiver with programmable logic

Abstract

A Global Positioning System (GPS) commercial receiver includes programmable logic that utilizes P-code modulated L1 and L2 GPS signals to derive estimates of in-phase and quadrature-phase components of both L1 and L2 signals, a programmable processor that calculates pseudoranges and pseudo-Doppler phases, and derives navigation solutions. In processing received L1 and L2 signals encrypted by an unknown W-code, a received comple L1 signal is multiplied by a locally-generated replica of the P-code, and integrated over a tim period having a duration that is approximately the same as the bit duration of the W-code. The received complex L2 signal is multiplied by a replica of the P-code, integrated, and latched to account for L2 signal delay relative to L1. In-phase components of the integrated signals are weighted proportionally to L1 and L2 signal amplitude, and the weighted sum is compared to zero and its magnitude is compared to a predefined threshold. Simultaneously, the integrated complex L2 signal is added to, or subtracted from a previously accumulated complex L2 signal in accordance with a sign of the weighted sum, and on condition that the magnitude of the weighted sum exceeds the predefined threshold. A resulting complex accumulated L2 signal comprises near-ML estimates of desired L2 amplitude and pseudo- Doppler phase.

Description

Background technique [0001] This disclosure relates generally to Global Positioning System (GPS) satellite receivers, and more particularly to their overall architecture and specific digital signal processing portions within such receivers. [0002] GPS satellites transmit spread spectrum signals on the L1 and L2 frequency bands at 154fo and 120fo, respectively, where fo = 10.23MHz. Each L1 signal is modulated by a C / A code and a P code unique to each satellite. Both codes are well known. Each L2 signal is only modulated by the P code. Although both the C / A code and the P code sequences are known, each GPS satellite provides the ability to modulate its P code by a secret signal commonly referred to as the W code. This "anti-spoofing" (A / S) allows the GPS system to be used in military applications by preventing jamming signals based on known P-codes from being interpreted as actual GPS signals. The combination of P code and W code is generally called Y code. [0003] Gaini...

AI Technical Summary

Problems solved by technology

For example, known receiver structures cannot take advantage of the new and more robust L2c code possibilities that will become available to civilian users

Known receiver architectures are generally difficult or impossible to adapt to new applications because they are implemented in application-specific integrated circuits (ASICs)

Additionally, such ASICs can be costly

[0005] In addition, known receiver architectures are generally highly energy and other resource consuming in order to process L1 and L2 signals in an acceptable manner

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