Measured performance of a DSP implementation of Doppler phasor recovery for DQPSK over mobile satellite channels

he recent trend towards digital modems over conventional analog modems has made the digital signal processor (DSP) a very useful tool. The focus of this thesis is the implementation of a digital modem on a pair of digital signal processing development boards and to test the implementation for the mobile, flat fading channels. The work presented here is an extension of the work accomplished in (1). The focus of (1) is the symbol timing recovery tracking loop in the presence of noise only. Some preliminary work with the use of polyphase interpolation filters for timing recovery was carried out in (1). That work is continued and the first laboratory results for a DSP based modem operating at 4800 bps are demonstrated.;The modem design is geared towards mobile satellite applications (MSAT). As such, the modem must be able to work in the presence of Doppler offsets and flat Rician fading. This thesis presents the simulation and laboratory performance of three Doppler phasor correcting algorithms. The algorithms use post-processing techniques and do not attempt to modify the receiver's local oscillator.;The performance of the symbol tracking algorithm and the Doppler tracking algorithms are examined in the presence of Rician fading for both filtered DQPSK and filtered...