The performance of QPSK (quadrature phase-shift keyed) systems using complex transversal filters with additional decision-feedback (DF) taps in the presence of multiple continuous wave (CW) interference and Gaussian noise is analyzed. General analytic expressions are derived for the optimum tap weights and minimum square errors in the presence of multiple CW interference for both one-sided and two-sided transversal filters with and without DF taps. It is followed that the output signal-to-noise ratio (SNR) of the one-sided DF filter is most improved, and that the output SNR is very insensitive to input signal-to-interference ratio. Analysis of the transient behavior of the DF filter shows that the magnitude of tap weights for large CW interference is larger than that for small interference, and that tap weights for a one-sided DF filter are more rapidly converged than those for a two-sided DF filter.
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|Published - 1987 12月 1
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