Reflective-Array Matched Filter for a 16-Pulse Radar Burst.
MASSACHUSETTS INST OF TECH LEXINGTON LINCOLN LAB
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A new type of matched filter has been designed and fabricated for a doppler-sensitive burst waveform with 16 equally spaced linear-FM subpulses, each of which has a 60MHz bandwidth and is 3 microsec long. The interpulse period is 5 microsec, and the total duration of the waveform is 80 microsec. The filter consists of 16 reflective-array-compressor sections ion-beam etched in the surface of a 15.2-cm-long Y-Z LiNbO sub 3 substrate. The reflective-array section for each subpulse is depth-weighted according to a Hamming function for range-sidelobe suppression, and the peak responses of successive sections have a Hamming weighting for doppler-sidelobe suppression. A reduction of system complexity and an improvement in dynamic range is expected with filters of this type as compared to conventional doppler burst processors. We have fabricated on one substrate a matched filter for an entire burst, thus providing the full correlation gain inherent in the waveform within a single device. This yields a large dynamic range despite a relatively high insertion loss 43 dB CW at center frequency 200 MHz for the central section. Within a given section, the phase deviations from quadratic are typically 5 deg. r.m.s. and corresponding range sidelobes are more than 30 dB down from the correlation peak. These phase deviations and the errors in delay between sections can be reduced by metal overlay patterns. A filter for the zero-doppler channel was built to operate at a temperature of 60 C. When the temperature is changed by 0.98 C, the peak response of this filter is shifted by an amount equal to the doppler resolution 18 kHz.
- Electrical and Electronic Equipment
- Active and Passive Radar Detection and Equipment