Parallel correlator for global positioning system receiver

• US 5,579,014 A
• Filed: 01/20/1995
• Issued: 11/26/1996
• Est. Priority Date: 01/20/1995
• Status: Expired due to Term

• Current Assignee: General Electric Company
• Original Assignee: General Electric Company
• Inventors: Brooksby, Glen W., Tiemann, Jerome J., Michon, Gerald J.
• Primary Examiner(s): Blum, Theodore M.
• Application Number:
  US08/376,211
• Time in Patent Office: 676 Days
• Field of Search: 342/357, 364/604, 364/728.03
• US Class Current: 342/357.69
• CPC Class Codes: G01S 19/09 providing processing capability normally carried out by the receiver
• CPC Class Codes: G01S 19/29 carrier including Doppler, related G01S19/246 takes precedence
• CPC Class Codes: G01S 19/30 code related G01S19/246 takes precedence
• CPC Class Codes: G01S 19/34 Power consumption

Abstract

A correlator for identifying global positioning satellites includes an antenna at a central location for receiving signature signals from a plurality of the satellites. Each received signal is converted from analog to digital form. A filter is employed to correlate each digital signal with a respective, unique code sequence. Each filtered digital signal is supplied to a circuit which produces an indication that identifies each satellite from the filtered digital signal supplied to the circuit.

Claims

1. A correlator for determining identities of a plurality of satellites comprising:

antenna means for receiving a unique signature signal from each one of a plurality of said satellites;

analog-to-digital converter means coupled to said antenna means for converting signature signals from analog form to digital form;

a capacitor matrix coupled to said analog-to-digital converter means, said matrix comprising a plurality of rows of capacitors wherein each of said capacitors in each respective row is weighted proportional to the signature signal of a respective one of said satellites such that each respective output signal of said capacitor matrix corresponds to the signature signal of a respective one of said satellites; and

output means coupled to said capacitor matrix for producing signals that identify said satellites according to their respective signature signals.

2. The correlator of claim 1 wherein each row of said capacitor matrix is weighted proportional to a Gold code sequence of a respective one of said satellites.

3. A parallel correlator for use in a space-based GPS system, said correlator having a predetermined number of channels, comprising:

antenna means for securing a plurality of coded signals transmitted from a plurality of global positioning satellites ranging up to a predetermined number;

analog-to-digital converter means coupled to said antenna means for converting the coded signals from analog form to digital form;

a plural stage shift register for receiving the digital signals from the analog-to-digital converter means and for producing a plurality of signals;

a filter comprising a matrix of capacitors, said matrix having a plurality of rows and columns of capacitors, the respective capacitance of capacitors disposed in a respective row of said matrix corresponding to at least one respective Gold code sequence transmitted by one of said satellites, each respective column of capacitors in said matrix being coupled to a respective stage of said shift register; and

output means coupled to each of said capacitor rows such that said output means is responsive to signals from said filter for producing a respective satellite identification signal for each of said satellites according to its respective Gold code.

4. A correlator for determining identity of a satellite comprising:

antenna means for receiving a signal from said satellite;

analog-to-digital converter means coupled to said antenna means for converting the received signal to a digital value;

filter means coupled to said analog-to-digital converter means, said filter means including a plurality of rows of capacitors wherein each capacitor value corresponds to a code unique to said satellite, said filter exhibiting a plurality of Doppler shifts of the signal received from said satellite when said filter is scanned with a local oscillator signal over a range of expected Doppler shifts and thereby producing an output signal that identifies the satellite by the detected Doppler shifts; and

output means coupled to said filter for displaying identification of said satellite as determined from said Doppler shifts.