Hughes Aircraft Company

John B Harrington

Michael Waldner

The pulse envelope of a chirped or phase coded pulse is separated from the phase modulation in such a way that the bandwidth of the signal output is decreased while the pulse width is maintained. This result is accomplished by injecting the pulse into two mixers coupled in parallel. The first mixer combines the coded pulse with a constant frequency signal generated by a local oscillator to obtain a resultant signal having an upper sideband whose phase is the sum of the phases of the coded pulse and a lower sideband whose phase is the difference between the phases of the two signals injected into the first mixer. The lower sideband of the resultant signal is filtered out with an upper sideband bandpass filter to obtain an upper sideband signal which is combined with the coded pulse in a second mixer. The second mixer output is phased through a lower sideband bandpass filter to obtain an output pulse having a phase independent of the phase of the coded pulse input, a pulse width equal to that of the coded pulse, and a pulse amplitude proportional to that of the coded pulse. Pulse compression in the frequency domain is therefore accomplished.

System for obtaining pulse compression in the frequency domain

A compressive or 'microscan' signal processor adapted for the simultaneous measurement of multifrequency signal components which encompass a broad frequency spectrum. In accordance with one embodiment of the invention, the applied signals are processed through a mixer which is driven by a linear frequency versus time waveform sweep signal. The output from the mixer is applied to one input port of a nonlinear correlator, and a second input port of the correlator is supplied with a linear frequency versus time waveform signal whose slope is opposite from that of the sweep signal applied to the mixer. The output signal from the correlator comprises a series of pulses which are displaced in time as a function of the frequency of the corresponding portions of the applied signals, and whose amplitudes are representative of the relative energy distribution of the applied signals.

Adjustable frequency scanning signal processor

The recirculating tapped delay line in accordance with the invention is a combination electrical and acoustic recirculation network that includes a selected number of acoustic surface wave circulating subloops included in an electrical primary feedback loop or network with each subloop having a selected number of taps. Each acoustic subloop includes track changing multistrip couplers that inject the signal into the loop, multistrip reflecting track changers at each end of the surface wave path, tapping transducers or multistrip couplers in both forward and reverse acoustic paths and a multistrip loop cancelling switch for suppressing the recirculating signal as desired. Because the recirculation is entirely acoustic in each subloop, the components which contribute substantially to distortion are utilized with less frequency so that the overall distortion after specific storage time is reduced. Also, by repeated recirculation through each subloop, a substantially larger effective number of taps may be realized per actual number of taps during each electrical feedback around the primary overall loop. The combination of primary and subloops in accordance with the invention effectively multiplies the actual number of taps in the subloops by the number of combined acoustic and electrical recirculations, all with a minimum of signal loss and distortion.

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Los Alamitos, CA, United States of America

John B Harrington