Abstract: An SSR reply decoding system for separating pulse codes of a series of closely-spaced or overlapping SSR replies is disclosed. A delay line is connected to receive pulses representing the leading edge of each SSR reply code pulse. The delay line has a length corresponding to at least two bracket lengths of an SSR reply. A bracket decoder is connected to respective taps of the delay line for determining the beginning and end of a first SSR reply. A phantom reply detector is connected to the remaining taps for inhibiting the bracket decoder when two replies are represented by pulses in the delay lines, one of the replies having a pulse space from the pulse of another reply equal to a framing pulse period for an SSR reply. The phantom reply detector therefore inhibits the detection of phantom replies. As a discriminate for determining when pulses having the spacing of a framing period belong to different replies, azimuth data is provided which will permit discrimination of these phantom conditions.

Abstract: A secondary surveillance radar system in which monopulse processing is used to obtain angle estimation of azimuth bearing, the improvement residing in a precision method, involving a monopulse qualifier signal, for identifying the maximum unambiguous off-boresight azimuth (OBA), while ensuring reduced sensitivity to Omni channel variations; the monopulse qualifier signal is developed from coherently combining the IF limited signals derived from the Sum+JDelta and Delta+jSum signals, such that two amplitude varying signals are created, such signals bearing a direct relationship to the Sum and Difference antenna pattern ratios and being independent of antenna signal power.