A relatively new modulation method, previously referred to as Q/sup 2/PSK, is described in further detail. An analysis for system bandwidth and bit error performance is given, along with results when the set of discrete prolate spheroidal sequences are used as the optimal pulse shaping functions. Particular attention is given to performance under channel bandlimiting, nonlinear transformations, and fading conditions.

The discrete prolate spheroidal sequences are optimum waveforms in many communication and signal processing applications because they comprise the most spectral efficient set of orthogonal sequences possible. Generation of the sequences has proven to be difficult in the past due to the absence of a closed form solution. A new method of easily generating any single discrete prolate spheroidal sequence, including sequences of very long length, is presented. Also shown are some example sequences generated using the algorithm presented.< >

A bit time estimator which uses adaptive filtering techniques is presented. The filter weights of an adaptive linear predictor are shown to provide a reliable estimate of the bit time T of a random binary square wave contaminated with additive white Gaussian noise, with little or no a priori information. The quality of this estimator is then evaluated via the least mean square algorithm, and a comparison is made between it and a more conventional estimator based on a zero crossing detector. This comparison shows that an adaptive estimator based on a linear predictor is generally superior

A numerical method is described for analyzing the performance of an acoustooptic receiver. The method provides output waveforms, probability density functions for samples of the output, and detection probabilities for output samples. The approach is general in that input pulse envelope shapes, pulse offset frequencies, and output rilter magnitude responses are arbitrary. The basic analysis is also independent of the shape of the optical beam and of the photodiode windows.

The development of numerical methods for studying the transient nonstationary behavior of a delay line discriminator is presented. Expressions are developed for the mean and the variance of the output noise process. For the cases where the output is stationary, power density spectra are found.

A numerical method is described for predicting the detection probability of a frequency compressive pulse receiver. The approach is general; i.e., input pulse envelope shapes, pulse offset frequencies, and filter magnitude responses are arbitrary. The performance of the frequency compressive receiver is analyzed and compared to that of a crystal video receiver for a specific case.

A numerical method is described for predicting the detection probability performance of a pulse receiver which uses square-law detection. The method is useful for receivers where the ratio of RF bandwidth to video bandwidth is in the range from 2 to 40; a range where numerical results have previously been hard to obtain. A key feature of the approach is that it takes into account the actual filter transfer functions, pulse envelope shape, and pulse frequency.

A technique is given for determining the error-rate performance of a class of digital communication systems operating with fading multipath interference. The approach uses a truncated series to represent the fading process and takes into account the effects of intersymbol interference caused by linear filtering in the receiver or channel. Application of the method to the cases of minimum shift keyed (MSK) and offset quadriphase shift key (OQPSK) systems reveals a slight performance advantage for MSK.

Relationships are derived for finding equivalent low-pass representations of the Volterra kernels corresponding to a widely used model for a nonlinear communication channel. The results are a logical extension of the usual complex envelope representation for bandpass signals. The equivalent low-pass representations are useful for simplifying calculations in cases where the input and output signals of the system are bandpass.

In the paper, we introduce the notion of short-term adaptive filtering via a sequential regression (SER) formulation. A corresponding short-term SER algorithm for nonrecursive filters is derived. Experimental results involving a short-term SER predictor are presented. For purposes of comparison, corresponding results using Widrow's least-mean-square (LMS), and the conventional SER algorithm are also included.

A digital simulation of a second-order phase-lock loop (PLL) acquiring lock in the presence of noise is reported. Since the system simulated includes lock-indicating circuitry, a distinction is made between the time to phase lock and the time to indicate lock. The parameter of interest is the time to indicate lock. The major results of the simulation are estimates of 1) the mean time to indicate l...

A new demodulator structure, the phase filter, is proposed for f.m.-threshold extension. A mathematical model is derived which shows the structure is equivalent to a conventional phase-lock loop preceded by a linear filter operating on the phase of the received signal.