Mutual Coupling Effects and Their Compensation in a Time-Delay Scanned Array of Irregular Subarrays

Abstract

A well-known array broadbanding technique employs rectangular subarrays to introduce time delay into phase scanned arrays. This practice results in large quantization lobes that grow with scan and frequency offset. Previous studies have shown that in the absence of mutual coupling, the use of irregular subarrays can eliminate these quantization lobes without significantly increasing the average sidelobe level. However, there has remained some concern that the phase discontinuity between subarrays would, through mutual coupling, further distort the aperture distribution and increase array sidelobes and reflections. This letter addresses the effect of mutual coupling in arrays of time-delayed subarrays and shows that the pattern distortion caused by mutual coupling in bandwidth systems is relatively small compared to the quantization lobes and can be completely eliminated at any one frequency (for "single mode" radiating elements) by selecting the proper incident voltage to compensate for the coupling. After compensation, any remaining sidelobes are due to the subarray phase discontinuity and are identical to those with mutual coupling neglected.

A Figure of Merit for Simultaneous-Multi-Beam Transmit Antenna Arrays

“…Alternatively, two or more single-beam subarrays can be spatially interwoven with each other or combined in blocks to create an SMB array [3], [8]. Most designs retain the λ/2 interelement spacing, which means that the number of antennas per beam is reduced in order to fit within the array aperture boundaries of the design.…”

“…It is difficult to directly compare the performance of different SMB designs, as the functionality can be achieved using very different architectures, e.g. subarrays [1], densely interleaved arrays [2], and others [3]. Each implementation either enforces some loss of efficiency or restricts the number of beams in some way that the system can support and as of yet, there is no direct manner of comparing their performance.…”