Theory of angle estimation using a multiarm spiral antenna

Abstract

An analysis of angle estimation using a single aperture, multimode spiral is presented. It is demonstrated that in addition to the classical Comparison method, modern parameter estimation techniques such as Multiple Signal Classification (MUSIC) and MLM (Maximum Likelihood Method) can be applied to multimode antenna technology for angle estimation. These techniques, coupled with the advent of digital receivers make possible the elimination of the mode-forming network. Results of computer simulations show that these new approaches give lower bias and variance, and also extend coverage toward boresight compared with the traditional Comparison method.

The effect of the number of modes and feed locations in angle-of-arrival estimation using a multimode antenna

“…To explore the effect of the number of modes on AOA estimation, the maximum likelihood method (MLM) described by Penno and Pasala [13] was used. The MLM compares the array response to an incident wave of arbitrary AOA to an array of steering vectors, known as the array manifold.…”

Modified current distribution for analysis of spiral antennas

“…Because of the spiral's wideband features, much attention has been given to this subject on recent literature. A particular application of the spiral antenna is direction finding and angle estimation [5], where the angle-ofarrival (AOA) is estimated by the amplitude and phase of the received signal. Using multi-arm spiral antenna, the amplitude and the relevant phase of different modes are related to the elevation AOA and azimuth AOA, respectively [6].…”

An improved hybrid interferometer

“…The first results shown in Figures (6)- (9), deal with the performance of these AOA determinations systems over a range of baselines, hut for two different SNR values of 10 dB and 4 dB. Here, the AOA was fixed at 0=40" and @=90' , equivalent to y-50".…”

“…It was seen that this process, previously described as Hybrid-MUSIC, eliminated the threshold phenomenon, producing AOA estimates completely free of the effects of the ambiguities that were problematic with the LPl and the Hybrid Interferometer. Moreover, the AOA estimates of Hybrid-MUSIC [9] were much improved over a wide band of frequencies beyond those of the LPI and the Hybrid-Interferometer. Unfortunately, application of MUSIC to the three spiral (1).…”

“…A coarse estimate produced by one o f two methods is then used to isolate the correct AOA solution. An alternative approach described in[9] involves concatenating the data matrices obtained from all three spirals in to a single data matrix. Let assumed that the noise present is white, Gaussian and zero-mean.…”