The direction finding (DF) performance of an array of vector sensor antennas on a small aircraft is assessed. DF performance in the presence of additive noise, array manifold perturbations, and uncertainty of polarization parameters is examined with simulated data and compared to the Cramer-Rao lower bound. DF performance improvements are demonstrated with a least-squares type calibration technique with and without the use of synthetic antenna elements.

Two recently published external array self-calibration algorithms are applied to experimental data obtained using a surveyed 12-element large sparse aperture array operating at 980 MHz. Though the algorithms are similar in that they use iterative methods to attempt to estimate the angle-of-arrival (AOA) of incoming signals with an imperfectly calibrated array, they are formulated quite differently. The performance of these algorithms is evaluated through their ability to reduce spurious peaks in direction finding (DF) spectra and accurately estimate the AOA of an incoming signal.

The symbol error probability of two selection schemes, namely, maximum signal-to-noise ratio (M gamma ) selection and maximum output (MO) selection, for M-ary multidiversity reception over a Rayleigh fading channel are discussed. The symbol error probability of the MO scheme is lower than that of the M gamma scheme. The more diversity receptions that are used, the larger is the difference. A simple expression of crossover average signal-to-noise ratio (per bit) is presented as a guideline for increasing the number of diversity receptions.>

For pt.I see ibid., vol.COM-3, no.12, p.1320 (1987). Ratio-statistic combining is proposed for mitigating partial-band interference in systems with diversity transmission and frequency-hop signaling. Systems with noncoherent demodulation and binary orthogonal signaling are covered. The partial-band interference is Gaussian, and Gaussian quiescent noise is included in the analysis to account for wideband noise sources. The exact probability of error is found for a receiver using ratio-statistic combining, and this is compared to the exact error probabilities for receivers with optimum combining with perfect side information, clipped-linear combining, the ratio-threshold test with majority-logic decoding, and self-normalization diversity combining. Numerical results are also given for a frequency-hop system which uses ratio-statistic combining for channels with Rayleigh fading and partial-band interference. It is determined that ratio-statistic combining is an excellent diversity combining scheme for systems with partial-band interference and fading.>

Diversity combining techniques that employ a ratiothreshold test (RTT) are suggested for communications with fading and partial-band interference. We consider a system with binary orthogonal signaling and noncoherent demodulation. The fading channel is modeled as a group of independent narrow-band channels, each with nonselective Rician fading. We assume that the partial-band interference is Gaussian, and we include additive white Gaussian quiescent noise in the analysis to account for wide-band noise sources. The performance measures we use to evaluate the diversity combining schemes are the narrow-band interference rejection capability and the signal-to-noise ratio requirement over the entire range of partial-band interference duty factors. The performances of the RTT with square-law combining and the RTT with majority logic decoding are compared to each other and to the performance of the optimum diversity combining technique.

Clipped-linear diversity combining is analyzed for receivers without side information. Communication systems with noncoherent demodulation, binary andM-ary orthogonal signaling, and diversity transmission are considered. The main source of interference is additive Gaussian partial-band interference, but a nonzero quiescent noise level is also included in the analysis to account for wide-band noise sources. Some of the results apply to general (non-Gaussian) interference. The numerical results demonstrate that clipped-linear combining can perform well in terms of both narrow-band interference rejection capability and maximum signal-to-interference ratio requirement. A practical disadvantage of clipped-linear combining is that it relies on measurements of the signal output voltage.