Low sidelobe pulse compressor
AssigneeThe United States of America as represented by the Secretary of the Navy
InventorsBernard L. Lewis, Frank F. Kretschmer
Life of this patent
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Abstract
A pulse compression system based on the transmission of a step approximat to linear FM pulse, and the subsequent processing of echos therefrom by converting the echo pulses to I and Q baseband signals and then sampling these I and Q signals at the Nyquist sampling rate. It has been discovered that this processing yields a signal with a spectrum substantially identical to the spectrum of a properly sampled Frank coded pulse. These sampled I and Q signals are then compressed by a Fast Fourier Transform compressor to yield a pulse with low sidelobes.
Claims6
A method of processing for use in a pulse-compression system which will yield low sidelobes comprising the steps of:
- generating a step-approximation to linear FM signal with N frequency steps;
- transmitting said signal;
- receiving echos from said transmitted signal;
- converting said received echos to baseband signals including the step of narrow band filtering said signal;
- digitizing said baseband signals at the Nyquist sampling rate for the baseband;
- Fast Fourier Transforming a set of N.sup.2 of said digitized samples and generating N outputs therefrom representing the passbands for the N transmitted frequency steps;
- differentially delaying said N passband outputs such that the passband outputs occur simultaneously;
- and
- adding said N differentially delayed outputs to form a single short pulse of a desired length, such that when an echo signal is properly indexed within said set of N.sup.2 digitized samples, then the resultant pulse has a peak amplitude.
A pulse compression system which will yield low sidelobes comprising:
- means for generating a step-approximation to linear FM signal with N frequency steps;
- means for transmitting said signal;
- means for receiving echos from said transmitted signal;
- means for converting said received echo signal to a baseband signal and including means for narrow band filtering said signal;
- means for digitizing said baseband signal at the Nyquist sampling rate for the baseband;
- Fast Fourier Transform means for weighting a discrete set of N.sup.2 digitized samples from said digitizing means and generating N outputs therefrom representing the passbands for the N transmitted frequency steps;
- means for differentially delaying said N passband outputs such that the N passband outputs occur simultaneously;
- and
- means for adding said differentially delayed outputs to form a single pulse, such that when an echo is properly indexed within a discrete set of N.sup.2 digitized samples, then a short pulse will be generated with a peak amplitude.
Dependencies are inferred from the claim text.