Abstract: An improved decoding technique useful for hard decision decoding, such as quadrature phase shift keying (PSK) and quadrature amplitude modulation (QAM), as well as soft-decision techniques, such as Viterbi decoding and trellis decoding. The system in accordance with the present invention provides adaptive decision regions for hard-decision decoding techniques and adaptive metrics for soft-decision detection techniques in which the decision boundaries and reference constellations, respectively are optimized in order to minimize the bit error rate (BER). In particular, the decision boundaries and metrics are optimized based on the locations of the received constellation points.

Abstract: A universal modulator architecture for generating various band efficient waveforms, such as QPSK 8 PSK, 16 PSK, 16 QAM, 12/4 QAM, 32 QAM and 64 QAM and higher. The modulator includes one or more biphase modulators coupled to one or more QPSK modulators. Each of the bi-phase modulators includes a pair of switchable attenuators for varying the degree of phase shift of the symbols to form the various constellations for the 8 PSK, 16 PSK, 16 QAM 12/4 QAM, 32 QAM and 64 QAM and higher signals. The architecture is expandable to generate higher order modulation formats, such as 256 QAM, 512 QAM and 1024 QAM and above. The architecture is also expandable to support non-linear predistortion.

Abstract: Apparatus and a corresponding method for predistorting an input signal applied to a radio frequency (RF) power amplifier, to compensate for amplifier distortion at high powers. The RF amplifier input and output signals are continuously monitored and difference signals are generated in an RF phase discriminator. The difference signals are converted to digital form and stored in a lookup table in the form of running averages of an RF amplifier gain compression value and an RF amplifier output phase value for each observed RF input power value. A predistorter module retrieves these values and predistorts the RF amplifier input by way of compensation.

Abstract: A universal modulator architecture for generating various band efficient waveforms, such as QPSK 8 PSK, 16 PSK, 16 QAM, 12/4 QAM, 32 QAM and 64 QAM and higher. The modulator includes one or more biphase modulators coupled to one or more QPSK modulators. Each of the bi-phase modulators includes a pair of switchable attenuators for varying the degree of phase shift of the symbols to form the various constellations for the 8 PSK, 16 PSK, 16 QAM 12/4 QAM, 32 QAM and 64 QAM and higher signals. The architecture is expandable to generate higher order modulation formats, such as 256 QAM, 512 QAM and 1024 QAM and above. The architecture is also expandable to support non-linear predistortion.

Abstract: An improved sequential threshold detection circuit for use in the receiver of a spread-spectrum communication system is disclosed wherein the improvement resides in the employment of a feedback circuit for maintaining a pre-selected constant median dismissal time. In the preferred embodiment the feedback circuit comprises a flip-flop (70), a very long time constant integrator (72), and a one-shot (74) connected between a comparator (64) and a summing amplifier (60) for varying a threshold bias voltage applied to the summing amplifier. In an alternative embodiment, the feedback circuit serves to selectively vary the gain of a variable gain amplifier (110) in such a manner to vary the individual trial and error dismissal times to provide a substantially constant median dismissal time over the entire detection process.