ULTRA HIGH BIT RATE (UP TO 1GBIT/S) BANDWIDTH EFFICIENT FQPSK ALL-DIGITAL MODULATOR/DEMODULATOR ARCHITECTURES AND NASA IMPLEMENTATIONS

Abstract

The paper presents ongoing efforts at NASA’s Goddard Space Flight Center and the Jet Propulsion Laboratory to develop ultra high bit rate bandwidth efficient FQPSK modulators and demodulators. The ability to transmit and receive ever-increasing amounts of extremely high rate data is an enduring challenge in the arena of near-earth space borne science missions. Reliable and efficient transmission of information at these data rates requires the use of power and bandwidth efficient modulations that exhibit low transmitter, receiver, and decoder complexity. Conventional high rate approaches for achieving spectral limiting typically employ sharp post amplifier filtering at the transmitter to limit the interference to the adjacent bands. However, using analog filtering alone can produce substantial intersymbol interference and other distortions that substantially affect the detection performance of the signal. In contrast, various theoretical classes of modulation waveforms can be tailored to provide varying degrees of bandwidth and power efficiency or robustness to non-linear transmitter distortions while incurring little or no performance losses. In order to realize many of these signal types, precise amplitude and phase control over the synthesis of these signals is required, typically necessitating the use of digital signal processing.