Quadriphase shift keyed adaptive equalizer
AssigneeMotorola, Inc.
InventorsCarl R. Ryan, James H. Stilwell
Life of this patent
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Abstract
A quadriphase shift keyed (QPSK) adaptive equalizer includes baseband inphase (I) and quadrature (Q) adaptive filters for receiving demodulated OPSK signals. The I and Q channel filters are designed to operate independent of each other and adapt their characteristics continuously in a predetermined manner in response to an incoming received QPSK signal, distorted in an unknown time varying manner.
Claims5
A quadraphase shift keyed (QPSK) adaptive equalizer having in-phase and quadrature channels for equalizing incoming demodulated QPSK signals, comrising:
- a. first and second tapped delay lines connected to received the demodulated signals and provide in-phase and quadrature output signals in the in-phase and the quadrature channels;
- b. means for developing error signals connected to an output of each of the in-phase and quadrature channels;
- and
- c. in-phase and quadrature filter means connected to receive the in-phase and quadrature output signals, respectively, and the error signals, each filter means including first and second adjustable components and independent equalizer coefficient generator means associated with each of said components for individually adjusting said associated components to minimize the error signals in each channel.
A quadraphase shift keyed (QPSK) adaptive equalizer for equalizing incoming demodulated QPSK signals, comprising:
- in-phase (I) and quadrature (Q) channel equalizer filters adapted to minimize the output error of the equalizer;
- first and second means for adjusting in-phase and quadrature channel equalizer filter operating characteristics, respectively;
- said first and said second means providing different adjustments to said in-phase channel equalizer filter and said quadrature channel equalizer filter continuously in response to the incoming QPSK signals which have been distorted in an unknown time varying manner differently for the in-phase and quadrature channels;
- tapped delay lines and equalizer coefficient generators for the I and Q channels;
- and
- a data estimater and a matched filter interposed between the outputs of the equalizer filters and inputs of the equalizer coefficient generators for the I and Q channels.
Dependencies are inferred from the claim text.