US 2004/0002331 A1Published application

Method and system for implementing a communications transceiver using modified GPS user equipment

AssigneeThe Charles Stark Draper Laboratory, Inc.

InventorsRichard L. Greenspan, Joseph M. Przyjemski

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Abstract

A communications transceiver is implemented by modifying a GPS user equipment. In a data reception mode, a communications signal that has a carrier frequency outside the L-band, and that has been phase modulated by a PN code and by data encoded therein, is received from a conventional L-band GPS antenna. The signal is downconverted to the L-band input frequency of the GPS transceiver, and subjected to automatic gain control. The GPS transceiver software is modified so as to recognize and replicate the PN code, and to demodulate the data-bearing signal. In the data transmission mode, the data to be transmitted are modulated onto the selected PN code sequence. The data-modulated PN signal is converted to a non L-band transmission frequency. Normal operation of the GPS transceiver navigation functions is maintained in parallel with the communications functions.

Claims22

Dependent claims

A method of implementing a communications transceiver using GPS (Global Positioning System) user equipment that includes a GPS transceiver connected to a conventional L-band GPS antenna, said method comprising performing a data reception function and performing a data transmission function;

wherein the step of performing said data reception function comprises:
(a) utilizing said conventional L-band GPS antenna to intercept at least one communications signal including an RF carrier modulated by a PN coded sequence having data modulated thereon, said RF carrier having a carrier frequency outside the L-band spectrum allocated for transmission of one or more GPS navigation signals from one or more orbiting satellites;
(b) providing a downconverter between said GPS antenna and said GPS receiver for downconverting said carrier frequency of said communications signal to an RF input frequency of said GPS receiver;
(c) providing an AGC (automatic gain control) circuit for controlling the amplitude of said downconverted communications signal so as to prevent interference to reception of said one or more GPS navigational signals;
and
(d) demodulating said down-converted communications signal to remove said PN (pseudorandom number) sequence and to detect data bits forming said data modulated thereon;
and wherein the step of performing said data transmission function comprises:
(e) modulating communications data onto said PN sequence, said communications data being unrelated to GPS navigational data;
(f) converting said data-modulated PN sequence onto an RF (radio-frequency) carrier signal for transmission, said RF carrier signal being at a carrier frequency other than L-band frequencies that are allocated to satellite navigation for transmission.

6 more elements

Dependencies are inferred from the claim text.