Ultra wideband radar transmitter employing synthesized short pulses

• US 5,146,616 A
• Filed: 06/27/1991
• Issued: 09/08/1992
• Est. Priority Date: 06/27/1991
• Status: Expired due to Term

• Current Assignee: Raytheon Company (Rtx Corporation)
• Original Assignee: Hughes Aircraft Company (Rtx Corporation)
• Inventors: Small, James G., Tang, Raymond
• Primary Examiner(s): TUBBESING, THEODORE
• Application Number:
  US07/722,621
• Time in Patent Office: 439 Days
• Field of Search: 342/13, 342/201, 342/202, 455/75, 455/76, 455/102, 455/119, 455/103
• US Class Current: 455/103
• CPC Class Codes: G01S 13/0209 Systems with very large relative bandwidth, i.e. larger than 10 %, e.g. baseband, pulse, carrier-free, ultrawideband
• CPC Class Codes: G01S 7/282 Transmitters

Abstract

A predetermined radar pulse train is formed in space by transmitting individual spectral components thereof. Thus, a train of extremely short pulses is obtained without switching a radio frequency signal on and off at a high rate. A crystal oscillator is coupled to a harmonic generator such as a comb generator. A power divider distributes the output of the harmonic generator to a multiplicity of final filter amplifiers. Each final filter amplifier has a phase-locked VCO circuit that provides frequency accuracy, spectral purity, low noise and frequency stability. Thus, each final filter amplifier provides one of the spectral components of the predetermined radar pulse train. The final filter amplifiers are coupled by duplexers to a broadband multiplexing feed such as a nested cup dipole feed that illuminates a reflector. On receive, the broadband multiplexing feed separates all the spectral components of the incoming pulse train. Each spectral component is coupled to its own narrow band receiver by the duplexers. One receiver is used to amplify and detect each spectral component. The signals from the receivers are coherently combined in a signal processor in which the signals add coherently and the noise signals do not. This provides a processing gain in signal to noise ratio corresponding to the total number of receivers. The output of the signal processor is applied to a radar display.

Claims

1. A phase coherent transmitter chain comprising;

a master oscillator;

a harmonic generator coupled to said master oscillator for developing an output signal containing all of the spectral components of a predetermined pulse train;

a power divider coupled to said harmonic generator for distributing said output signal;

a plurality of final filter amplifiers coupled to said power divider that are responsive to said output signal developed by said harmonic generator, each of said plurality of final filter amplifiers adapted to amplify one spectral component of said predetermined pulse train, each of said plurality of final filter amplifiers comprising a voltage controlled oscillator, a phase lock amplifier and a mixer connected as a phase-locked VCO circuit;

a plurality of duplexers each individually coupled to the output of a different one of said plurality of final filter amplifiers; and

a broadband multiplexing feed coupled to said plurality of duplexers and having an aperture.

2. The phase coherent transmitter chain of claim 1 wherein said harmonic generator comprises a comb generator.

3. The phase coherent transmitter chain of claim 1 wherein said broadband multiplexing feed comprises a nested cup dipole feed.

4. The phase coherent transmitter chain of claim 1 wherein said broadband multiplexing feed comprises a multi-frequency band phased array antenna.

5. A phase coherent transmitter chain comprising;

a master oscillator;

a harmonic generator coupled to said master oscillator for developing an output signal containing all of the spectral components of a predetermined pulse train;

a 1;

n power divider coupled to said harmonic generator for distributing said output signal;

a plurality of final filter amplifiers coupled to said power divider that are responsive to said output signal developed by said harmonic generator, each of said plurality of final filter amplifiers adapted to amplify one spectral component of said predetermined pulse train, each of said plurality of final filter amplifiers comprising a voltage controlled oscillator, a phase lock amplifier and a mixer connected as a phase-locked VCO circuit;

a plurality of duplexers each individually coupled to the output of a different one of said plurality of final filter amplifiers;

a broadband multiplexing feed coupled to said plurality of duplexers and having an aperture; and

a reflector having a focal point disposed at the aperture of said broadband multiplexing feed.