Decision Feedback Carrier Recovery Research Articles

Performance of an MPSK correlation demodulator with decision feedback carrier recovery in the presence of a speech signal

The performance of a Correlation Demodulator (CD) with Decision Feedback Carrier Recovery (DFCR) in a channel with an additive mixture of a speech signal and a Gaussian background noise as interference is analyzed. The MPSK modulation format is considered. Expressions of energy loss due to the influence of the speech signal and of the probability of error are obtained. For this purpose the speech signal is considered as a random combination of vowels, consonants and pauses. Moreover, the vowels as well as the consonants are modeled as the response of some Linear Time Invariant (LTI) systems to white Gaussian noise. An experiment was performed. Good agreement with the theoretical results was obtained.

Performance of Coherent Phase and Amplitude Digital Modulations with Carrier Recovery Noise

A model of decision feedback carrier recovery noise is presented as a function of the number of symbols over which the carrier is derived. For this model, quantitative results for performance degradation in BPSK, QPSK, 8-phase, 16-QAM, 32-QAM, and 64-QAM coherent demodulators are presented. When the carrier is derived from only the last symbol, these results reduce to the performance for differential detection. Carrier integration over 100 symbols is shown to be adequate to provide performance quite close to ideal for all the modulations considered.

Analysis of Four Decision-Feedback Carrier Recovery Loops in the Presence of Intersymbol Interference

The performance of four decision-feedback carrier recovery techniques is evaluated in the presence of additive noise and intersymbol interference (ISI). For QAM signal constellations, a closed-form expression is given for the phase jitter variance (PJV) of each loop, and the loop tracking performance is examined. The analytic results are then computed in the case of a 16 QAM digital radio system subjected to multipath fading. Two cases are considered: in the first case no countermeasure techniques are used against selective fading, while in the second case a three-coefficient decision-feedback equalizer (DFE) is used. Computer simulations using a pseudorandom sequence to estimate loop performance are also reported which support the theoretical results.