Radar apparatus and method
First Claim
1. A method of determining the range of a radar signal reflecting object which method comprises the steps of generating a radar frequency carrier wave,(1) modulating said carrier wave with a first code having a first bit rate and a first code repetition rate,(2) modulating said carrier wave with a second code having a bit rate equal to and synchronous with said first code repetition rate,(3) transmitting said modulated carrier wave as a radar signal,(4) feeding a received echo to an analogue correlator whereto is also fed a delayed version of said first code,(5) and feeding an output of said analogue correlator via a down converter to a digital correlator for correlation therein with said second code,whereby a received echo correlated in said analogue correlator provides information as to a range cell wherein the reflecting object lies and correlation of the output of the analogue correlator in the digital correlator provides information as to a range band in which the range cell lies.
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Accused Products
Abstract
The invention provides a method of determining the range of a radar signal reflecting object by utilizing a radar frequency carrier wave modulated by a first short code having a first repetition rate and a second code having a bit rate equal to the first code repetition rate. A received echo is first passed to an analogue correlator for correlation against a delayed version of the first code, and the output of the analogue correlator is fed to a digital correlator for correlation therein against the second code. In this way, the high bandwidth (greater range resolution) of analogue correlation can be combined with the lower bandwidth (longer ambiguity function) of digital correlation to provide high resolution target detection without ambiguity and at a fast rate without the need for a very large number of correlators.
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Citations
17 Claims
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1. A method of determining the range of a radar signal reflecting object which method comprises the steps of generating a radar frequency carrier wave,
(1) modulating said carrier wave with a first code having a first bit rate and a first code repetition rate, (2) modulating said carrier wave with a second code having a bit rate equal to and synchronous with said first code repetition rate, (3) transmitting said modulated carrier wave as a radar signal, (4) feeding a received echo to an analogue correlator whereto is also fed a delayed version of said first code, (5) and feeding an output of said analogue correlator via a down converter to a digital correlator for correlation therein with said second code, whereby a received echo correlated in said analogue correlator provides information as to a range cell wherein the reflecting object lies and correlation of the output of the analogue correlator in the digital correlator provides information as to a range band in which the range cell lies.
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12. A radar apparatus comprising
(1) means for propagating a radar signal comprising a radar frequency carrier wave modulated by a first code having a first bit rate and a first repetition rate and a second code having a second bit rate equal to and synchronous with said first code repetition rate, (2) means for receiving a radar signal echo and for feeding the echo to an analogue correlator, (3) means for feeding a delayed version of said propagated radar signal to said analogue correlator, (4) a digital correlator whereto an output of the analogue correlator is fed, and (5) indicator means for indicating digital correlation of the analogue correlator output with the second code.
Specification