Abstract: A timing recovery loop includes a random walk filter counter for counting early, nominal and late arrivals of data transitions pulses of an input baseband signal waveform encoding a digital bit stream, and provides magnitude counts that are compared to a threshold value that when exceeded by the magnitude counts results in a delay adjustment of the generated adjusted timing pulses then remaining synchronized with the actual bit timing for maintaining bit timing lock. The adjusted timing pulses can then be used by a data detector for reliable data detection and reconstruction of the digital bit stream. The threshold value can be adaptively adjusted for reducing drop lock rates in the presence of changing channel environments.

Abstract: An adaptive predistorter system receives and predistorts an input signal so as to linearize the output signal of a nonlinear high power amplifier amplifying the predistorted input signal using closed-loop feedback of the output signal in complex form at baseband so as to adaptively change the amount of the predistortion of the input signal in the presence of high power amplifier changing characteristics.

Abstract: A polyphase channelizer converts an intermediate frequency wideband signal into a complex signal that is sampled by parallel analog-to-digital converters having a bank of samplers respectively clocked by staggered clocking signals for respective converters for feeding I and Q quadrature samples to a polyphase filter bank of finite impulse response filters driving a fast Fourier transform processor for providing channelized digital signal outputs. The parallel analog-to-digital converters can operate at lower speeds but are parallel connected for effectively operating at required higher speeds. The channelizer channelizes the wideband signal using a polyphase clock for enabling high speed sampling and converting through low speed parallel analog to digital converters.

Abstract: A predistortion method uses an extended Saleh model for linearizing the output of nonlinear high power amplifiers having inherent amplitude modulation to amplitude modulation distortion, and inherent amplitude modulation to phase modulation distortion, during conversions of an input signal to an output signal. A complex baseband linearizer provides predistortion at baseband for reducing spectral regrowth and improves bit error performance. The predistortion effects are matched to the amplifier distortions to cancel out the distortions to provide linearized conversions. The extended Saleh model provides a general solution using selected coefficients matched to distortion effects of a particular amplifier.

Abstract: A GMSK timing recovery loop in a receiver of a Gaussian Minimum Shift Keying (GMSK) link with a low channel Bit Signal-to-Noise Ratio (BSNR) and a small bandwidth-bit period BT product in a high bandwidth efficiency channel, includes a hard limiter for converting at baseband a GMSK demodulated received signal into a hard clocking signal clocking a conventional digital tracking transition loop generating the bit timing signal in closed loop control for stable time tracking performance for coherent demodulation of GMSK signals. The hard limiter provides the hard clocking signal at baseband having transitions at multiple bit periods adjusted by the bit timing error signal from the digital tracking transition loop for providing reduced jitter of the bit timing signal for accurate timing recovery and detection of communicated data.

Abstract: A predistortion method use a modified linear-log model for linearizing the output of nonlinear high power amplifiers having inherent amplitude modulation to amplitude modulation distortion, and inherent amplitude modulation to phase modulation distortion, during conversions of an input signal to an output signal. A complex baseband linearizer provides predistortion at baseband for reducing spectral regrowth and improves bit error performance. The predistortion effects are matched to the amplifier distortions to cancel out the distortions to provide linearized conversions. The modified linear-log model is used to reduce the clipping effects through the peak operating point for a specified output power loss with minimum distortion.

Abstract: An improved Gaussian minimum shift keying (GMSK) carrier tracking loop operating at baseband takes advantage of the orthogonality of precoded data GMSK signals and Laurent filtering to provide a carrier phase error signal generated at baseband for carrier phase derotation of the received GMSK signal. The carrier tracking loop also provides demodulated data estimates with performance equal to that of a GMSK serial demodulator. The tracking loop uses data directed feedback to improve noise rejection, but still has fast acquisition by operating at baseband.

Abstract: A demodulator for OQPSK signals modulated with two unique words resolves eight possible cominbations of phase ambiguity which may product data error by first processing received I.sub.R and Q.sub.R data in an integrated carrier loop/symbol synchronizer using a digital Costas loop with matched filters for correcting four of eight possible phase lock errors, and then the remaining four using a phase ambiguity resolver which detects the unique words to not only reverse the received I.sub.R and Q.sub.R data channels, but to also invert (complement) the I.sub.R and/or Q.sub.R data, or to at least complement the I.sub.R and Q.sub.R data for systems using nontransparent codes that do not have rotation direction ambiguity.