Sponsorship: US Air Force Grant FA9302-05-C-0001. A detector architecture capable of detecting both shaped offset quadrature phase shift keying (SOQPSK-TG) and Feher's quadrature phase shift keying (FQPSK-JR) is developed and analyzed. Both modulations are embodied as fully interoperable modulations in the Interrange Instrumentation Group (IRIG) standard IRIG-106. It is shown that the common detector achieves near optimal bit error rate performance without knowledge of which modulation is used by the transmitter. The detection techniques are based on a common trellis-coded modulation representation and a common continuous phase modulation (CPM) representation for these two modulations. In addition the common pulse amplitude modulation (PAM) decomposition of the common CPM representation is developed. The common PAM-based detector offers the best performance-complexity trade-off among the detectors considered.