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The prime objective of the UHF adaptive array processor program was to develop an adaptive array to provide rejection of interference in Naval communications systems. The major goals were: maximizing the signal-to-noise and signal-to-interference ratios, suppressing jammers over a 10 MHz bandwidth, operating with any four-element antenna array, and accommodating a wide range of jammer and signal waveforms.

This report investigates the performance which can be obtained by utilizing adaptive arrays to suppress undesired signals in coded communications systems. Emphasis is placed on determining the factors which limit the rate at which the array can respond to a time-varying signal environment, e.g., the environment which exists in a time-division multiple access (TDMA) communication system. The performance of adaptive arrays implemented with the LMS algorithm is evaluated analytically and experimentally. The direct matrix inversion algorithm is also investigated analytically to compare LMS algorithm response with the response obtained when estimates of the input signal parameters required to implement an optimal array processor are used in a direct manner to calculate the adaptive array weights.

Three related experimental studies analyzed rate and accuracy of test response under time-limit and no-time-limit conditions. Test instructions and multiple-choice vocabulary items were administered by computer. Student volunteers received monetary rewards under both testing conditions. In the first study college students were blocked into high- and low-ability groups on the basis of pretest scores. Results for both ability groups showed: (1) Higher response rates under time-limit conditions than under no-time-limit conditions; and (2) No significant differences between time-limit and no-time-limit accuracy scores. In the other tests, conditions were varied further. All three studies showed essentially zero correlations between response rate and response accuracy. Response latency data were also analyzed. These data suggested the existence of different test-taking styles and strategies under time-limit and no-time-limit testing conditions. The results of these studies suggest that number-correct scores from time-limit tests are a complex function of response rate, response accuracy, test-taking style and test-taking strategy, and therefore are not likely to be as valid or useful as number-correct scores from no-time-limit-tests.

Experimental results are given which augment the technological basis established previously for designing and instrumenting time division multiple access (TDMA) satellite communications systems, in which two coupled sampled- data delay lock loops are used to perform the timing functions. Emphasis is placed on presenting information needed to design TDMA system synchronizers when only coarse estimates of signal parameters and the instantaneous system geometry are available a prior.