High-resolution residue antenna architectures for wideband direction finding

Abstract

The performance of two novel interferometer antenna architectures for high resolution, wideband direction finding are investigated. The first configuration incorporates a Symmetrical Number System (SNS) encoding of the interferometer amplitude response (symmetrical folding waveform). The second configuration incorporates a Residue Number System (RNS) encoding of the interferometer phase response (saw tooth waveform). The residue architectures serve as a source for resolution enhancement in an interferometer array by decomposing the analog spatial filtering operation into a number of parallel sub-operations (moduli) that are of smaller computational complexity. Each sub- operation only requires a precision in accordance with the size of the modulus. A much higher resolution is achieved after the N moduli are used and the results of these low precision sub-operations are recombined. A four-element, 3 channel array using the moduli set m1 = 3, m2 = 4 and m3 = 5 was constructed in a ground plane using rectangular waveguide elements with a center frequency of 8.5 GHz. Experimental results are compared with the simulation results to demonstrate the advantages of this approach. The frequency response of the RNS array is investigated numerically. To correct the quantization errors due to any frequency offset, a fast correction algorithm is derived and is shown to have excellent results over a wide bandwidth.