Software that performs the functions of an FQPSK-B receiver (and to some extent, an FQPSK-B transmitter) has been developed to reduce the risks and costs associated with the development of hardware FQPSK-B transmitters and receivers. (“FQPSK-B” signifies version B of Feher Quadrature-Phase-Shift Keying, which is a patented, bandwidth-efficient phase-modulation scheme named after its inventor. FQPSK-B includes filtering, beyond that of FQPSK, for further containment of the modulation spectrum.) This software can be especially helpful to engineers who are considering the use of FQPSK-B for bandwidth- efficient, high-data-rate digital communications.

The FQPSK-B software receiver is an off-line coherent receiver that can be used as a stand-alone FQPSK-B receiver or as a means of testing and evaluating hardware FQPSK-B receivers, transmitters, and transceivers. The software can be customized for testing and validating hardware FQPSK-B transceivers under consideration for purchase. To satisfy requirements pertaining to testing, the receiver contains an internal reference transmitter and a simple additive- white-Gaussian-noise (AWGN) channel; hence, the software receiver can also be used as a test bed for endto- end simulations of FQPSK-B communication systems.

The software consists of many modules that perform diverse functions, including differential encoding, generation of FQPSK waveforms, modulation, AWGN channel model, carrier and symbol synchronizations, coherent demodulation and detection, differential decoding, real-time performance monitoring, and postprocessing of data to generate results of tests. The modules can be configured to carry out specific tasks in each of four different modes of operation of the receiver.

The software receiver was developed on a Sun workstation by use of the Matlab version 5.3 technical-computing software with such Simulink software libraries as the Communication Toolbox and the DSP Toolbox. The software receiver can be implemented on computers that utilize such operating systems as UNIX, Windows, and MacOS, as long as proper versions of Matlab/Simulink are installed. Moreover, because of the similarity between FQPSK and other phase-modulation schemes in the QPSK family, the software can readily be modified to accommodate those schemes.

This work was done by Haiping Tsou, Scott Darden, and Tsun-Yee Yan of Caltech for NASA’s Jet Propulsion Laboratory.

This software is available for commercial licensing. Please contact Don Hart of the California Institute of Technology at (818) 393- 3425. Refer to NPO-21050.

This Brief includes a Technical Support Package (TSP).
An Off-Line FQPSK-B Software Reciever

(reference NPO-21050) is currently available for download from the TSP library.

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This article first appeared in the November, 2002 issue of NASA Tech Briefs Magazine.

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