An iterative method that combines a parametric channel model with the maximum likelihood and cross-correlation estimation techniques has been developed to estimate the reflection, creeping wave, and times of arrival (TOAs) from an echo (backscatter) emanating from a rigid acoustic sphere. The modelled echo is assumed to be more complex than a linear combination of delayed and scaled versions of the transmitted pulse, and the individual backscatter pulses need not be disjoint. Experimental results demonstrate that the algorithm is successful in determining the proper time delays of the reflection and the creeping wave for a variety of received signal-to-noise ratios (SNRs).

Standard references show the effects of carrier phase jitter on the performance of digital communications equipment as curves of bit error rate versus signal-to-noise ratio for constant values of jitter variance. In any real system, the variance consists of a relatively small constant component and a component which is inversely proportional to signal-to-noise ratio. This correspondence presents revised calculations of bit error rate for a number of values of the constant variance component and the proportionality constant. The resulting curves are shown to agree with experimental results, and are useful for predicting performance of real systems.

This correspondence presents an improved technique for receive error detecting a pseudorandom digital sequence suitable for bit error performance testing of serial digital transmission systems. The method is applicable to separately located transmit and receive sites, is self-synchronizing, and can be economically constructed using logic elements and medium-scale integrated (MSI) devices from commercially available logic families.