AN ANALYSIS OF A SYSTEM OF PULSE CODING FOR CLUTTER SUPPRESSION.
Final rept. on phase 1,
NAVAL RESEARCH LAB WASHINGTON D C
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A system of pulse coding to reduce the effect of ground clutter on airborne search radars was examined and found to be of questionable value for a search radar, although other applications may exist now and in the future. The system would suppress a selected group of lines in the transmitted spectrum by means of a proper combination of the amplitudes, phases, and pulse spacings of a small group of successive pulses. The conditions for this suppression are examined in detail for an infinitely long series of pulse groups, and it is found that with a group of N pulses, N-1 spectrum lines may be suppressed. These lines may be any group of N-1, but it is shown that if they are symmetrically placed about the carrier, the rf phase angles are phi and phi pi radians. The first-order effects on the line suppression of variations from the nominal values of the parameters are analyzed, and it is shown that variations in the interpulse spacing must be kept below 1-12 parts in 100,000, the phase to within 0.1 degree, and the amplitude to within 1 part in 100,000 for reliable detection with a 40-db clutter-to-signal ratio. Finally, the effect of finite dwell time is examined, and it is shown that under the same conditions as above at least several thousand pulse groups need to be processed, which would require a time on target of about 18 sec. Author
- Active and Passive Radar Detection and Equipment