FQPSK Doubles Spectral Efficiency of Telemetry: Advances and Initial Air to Ground Flight Tests

Abstract

FQPSK is the abbreviation for Feher Quadrature Phase Shift Keying (FQPSK) patented systems [1]. Digcom, Inc. licensed FQPSK products demonstrated significant spectral saving and RF power efficient robust BER performance advantages. These bit rate agile modems and Non Linearly Amplified (NLA) transceivers, DSP and hardware implementations, and in some instances “software-radios” (20kb/s to more than 100Mb/s) and RF frequency agile (from 150MHz to more than 40GHz) developments and systems have recently been demonstrated and deployed. The spectral efficiency, i.e., data throughput capability of the 1st generation of FQPSK, as demonstrated in initial Advanced Range Telemetry (ARTM) flight tests, approximately doubles while 2nd generation “FQPSK-2” systems have the potential to quadruple the spectral efficiency of operational PCM/FM telemetry systems and be backward compatible with the 1st generation of FQPSK technologies. It is also demonstrated that the spectral efficiency advantage of FQPSK over that of NLA power efficient GMSK, OQPSK and QPSK modulated transceivers is in the 50% to 300% range and that the potential spectral efficiency advantage of FQPSK-2 over GMSK [1] is in the 200% to 500% range. Based on extensive multi-year studies of alternative solutions for spectral and RF power efficient, robust BER performance systems, several commercial US and international organizations, AIAA, CCSDS, NASA, ESA, CCSDS and various programs of the US Department of Defense (DoD) concluded that FQPSK offers the most spectrally efficient high performance-high speed proven technology solutions and recommended FQPSK standardization for several data links. Initial DoD-ARTM Program Office Air-to-Ground L-band and S-band jet airborne telemetry Test and Evaluation (T&E) data, obtained during the summer of 1998 are briefly highlighted. These include simultaneosly tested FQPSK and PCM/FM. In these tests the following ARTM objectives have been demonstrated: (a) FQPSK approximately doubles the spectral efficiency of currently operational PCM/FM; (b) The Data Link Performance of these two systems is comparable. The American Institute of Aeronautics and Astronautics (AIAA) draft modulation standard recommended to the DoD, NASA and CCSDS, was approved by the AIAA [23]. The AIAA standard recommends “that FQPSK modulation be immediately adopted as the interim increment–1 standard.”