US 4,894,660 AGranted

Range sidelobe reduction by aperiodic swept-frequency subpulses

AssigneeGeneral Electric Company

InventorsDon N. Thomson, David E. Maron

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Abstract

A swept-frequency radar system transmits pulses consisting of swept-frequency subpulses of nonuniform duration separated by short nontransmitting periods during which an array antenna is resteered. The pulses reflected from a target are processed by a method including estimating the target ranges, producing a reference signal at the time at which the pulse reflected from the target is expected to return. The reflected pulse is phase detected by means of the reference pulse to produce phase detected signals which include information relating to the error between the actual range and the estimated range. The phase detected signals are Fourier transformed to produce range error information. The nonuniform subpulse durations reduce the magnitude of range sidelobes.

Claims12

Dependent claims

A method for determining the range of a distant target, comprising the steps of:

steering the phase control elements of an array antenna to direct the antenna beam toward the target;
applying a sequence of pulses of carrier to said antenna for transmission, each of said pulses including a plurality of sequential subpulses, each of said subpulses being of carrier of monotonically changing frequency, said plurality of subpulses having nonuniform durations and being separated by nontransmitting periods of constant duration;
estimating the range to said target, and for each of said pulses generating a reference signal comprising at least a part of said plurality of sequential subpulses at a time corresponding to the expected time of return of a reflection from said target;
in the period between said pulses, receiving returned signal from said target and phase detecting said returned signal by use of said reference signal to produce phase detected signals including information relating to the error between the actual range and the estimated range;
and
Fourier transforming said phase detected signals to generate range error information.

3 more elements

Dependencies are inferred from the claim text.