Receivers for navigation satellite systems

• US 4,601,005 A
• Filed: 12/14/1982
• Issued: 07/15/1986
• Est. Priority Date: 12/31/1981
• Status: Expired due to Term

• Current Assignee: Qinetiq Limited (QinetiQ Group PLC)
• Original Assignee: The secretary of state for defence in her Britannic Majesty's Government of the United Kingdom of Great Britain And Northern Ireland
• Inventors: Kilvington, John
• Primary Examiner(s): Gruber, Felix D.
• Application Number:
  US06/449,789
• Time in Patent Office: 1,309 Days
• Field of Search: 364/456, 364/460, 364/726, 364/724, 364/443, 364/444, 364/445, 364/602, 364/604, 343/5 FT, 343/352, 343/378, 343/394, 375/1, 375/15, 455/209, 455/213, 455/225
• US Class Current: 708/3
• CPC Class Codes: G01S 19/30 code related G01S19/246 takes precedence

Abstract

A receiver for a navigation satellite system such as NAVSTAR, including an antenna for receiving an incoming coded, time-based, spread spectrum signal which includes navigational data from a plurality, P, of satellites, a circuit for deriving baseband I and Q components of each of the signals, circuitry for digitizing the I and Q components, a Fast Fourier Transform (FFT) processor for transforming the digitized I and Q components and their respective codes, and a multiplier for multiplying together the transformed components and codes derived for each of the P satellite signals and to inverse transform the signals and to then determine correlation peaks in the inverse transformed signals.

Claims

1. A navigation satellite system receiver comprising:

an antenna for receiving an incoming coded, time-based, spread-spectrum, continuous signal which includes navigational data from a plurality, P, of satellites; and

convolver means, connected to receive signals from said antenna for (a) convolving segments of said signal with codes therein by Fourier transforming said segments, (b) cyclically shifting points of the Fourier transform to produce a transform of a near baseband signal, (c) multiplying said shifted points with corresponding points of a pre-computed transform of a segment of spread spectrum code to give a resultant signal, and (d) inverse transforming said resultant signal to produce a correlation peak at a point having a position which gives the relative shift between said incoming signal and said code.

2. A receiver for a navigation satellite system, comprising:

an antenna adapted to receive coded, time-based, spreadspectrum, continuous signals which include navigational data from a plurality, P, of satellites;

means connected to said antenna for deriving baseband I and Q components from said signals;

means for digitizing said I and Q components;

a Fast Fourier Transform processor connected to receive said digitized I and Q components and to transform said components and their respective codes and to provide a first transformed signal;

multiplier means connected to said processor, for receiving said first transformed signal and multiplying together said transformed components and their codes to provide a multiplied signal;

an inverse Fast Fourier Transform processor connected to said multiplier means, for inverse transforming said multiplied signal and providing a second transformed signal; and

amplitude scanning means connected to said inverse Fast Fourier Transform processor, for determining correlation peaks in said second transformed signal.

3. A receiver for a navigation satellite system, having an antenna adapted to receive coded, time-based, spreadspectrum, continuous signals which include navigational data from a plurality, P, of satellites, comprising:

means connected to said antenna for deriving baseband I and Q components from said signals;

means for digitizing said I and Q components;

a Faster Fourier Transform processor connected to receive said digitized I and Q components and to transform said components and their respective codes and to provide a first transformed signal;

multiplier means connected to said processor, for receiving said first transformed signal and multiplying together said transformed components and their codes to provide a multiplied signal;

an inverse Fast Fourier Transform processor connected to said multiplier means, for inverse transforming said multiplied signal and providing a second transformed signal; and

amplitude scanning means connected to said inverse Fast Fourier Transform processor, for determining correlation peaks in said second transformed signal.