Raytheon Company

Wesley G Brodsky

Robert G Curtis

Steven Washakowski

A baseband shaping device includes a plurality of coefficient memories, each memory having an input address bus, a multiplexor input and a coefficient value output. The device further includes a plurality shift registers, each having an input coupled to a respective one of the coefficient value outputs, a digital to analog clock input and an output. The device further includes a plurality of negative value circuits, each circuit having an input coupled to a respective one of the first shift register outputs and an output, a plurality of multiplexors, each having a first input coupled to a respective one of the first shift register outputs and a second input coupled to a respective one of the output of the plurality of negative value circuits. The device further includes a plurality of second shift registers, and an adder having a plurality of inputs coupled to the plurality of second shift registers.

Method and device for pulse shaping QPSK signals

A truncated maximum likelihood sequence estimator that provides a best estimate of a transmitted symbol sequence includes a lookup table and a comparator. The lookup table may be responsive to at least a next sample of a received RF signal, a first decision made on a first previous sample of the RF received signal and a second decision made on the second previous sample of the RF received signal. The lookup table provides at an output at least one threshold value stored in the lookup table that is addressed by the next sample of the received signal, the first decision made on the first previous sample and the second decision made on the second previous sample. The comparator is coupled to the output of a lookup table and is responsive to the at least one threshold value and a current sample of the received RF signal. The comparator compares the current sample of the received RF signal with at least one threshold value and provides a best estimate of the transmitted symbol sequence. The truncated maximum likelihood sequence estimator can be used for example to determine a best estimate of a transmitted symbol sequence of a current sample of 4-ary frequency shift keyed signal or a 2-ary frequency shift keyed received signal. In addition, the truncated maximum likelihood estimator can be used within a wireless radio that transmits and receives an RF waveform including a modulated symbol stream to provide the best estimate of the received modulated symbol stream. Further, the truncated maximum likelihood estimator can be used within a wireless local area network that includes at least one computer interfaced to a wireless radio containing the truncated maximum likelihood sequence estimator to provide wireless communications between either computers or between a computer and a computer network.

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Medford, MA, United States of America

Wesley G Brodsky