Thinned Spiral and Diffused-Configuration Ka-Band SATCOM Phased Arrays With ±60° Beam Scanning

In this article, we propose a novel method for thinning phased arrays with circular apertures, utilizing a spiral configuration of elements. A comparative study is presented between two types of thinned planar arrays—spiral and conventional diffused thinned arrays. The performance of these arrays is verified using four different filled fractions, occupying 64%, 50%, 32%, and 25% of the element count of an 812-element circular aperture. The measurements were conducted primarily at 29 GHz using a $Ka$ -band satellite communication (SATCOM) transmit phased array. The results demonstrate that both types of arrays exhibit wide scan angles of up to ±60° while keeping the sidelobe levels (SLLs) below −12.5 dB. Specifically, spiral arrays are capable of achieving near-diffraction-limited patterns at wide scan angles. Additionally, both arrays exhibit a similar frequency response to the reference aperture, thus maintaining the operation bandwidth. Application areas are in low-earth orbit (LEO) SATCOM phased arrays or mm-wave imaging systems with a reduced number of elements with diffraction-limited beams and where higher SLLs may be tolerated.

I. Introduction

Irregular arrays have been studied to meet the evolving requirements and constraints on phased arrays with their various applications, such as satellite communications (SATCOMs), radar, and sensing systems. Previous studies suggested various irregular array architectures, including randomly grouped subarrays or elements, thinned, sparse, and time-modulated arrays [1], [2], [3], [4], [5], [6], [7], [8], [9], [10], [11], [12], [13], [14]. Thinned arrays, which are characterized by an irregular distribution of selectively turned on/off radiating elements on a regular array, have emerged as a promising irregular array architecture (Fig. 1). By appropriately arranging the active elements, thinned arrays can achieve desired radiation patterns with fewer elements. Thinned arrays have practical importance for modern applications that require lightweight design, low energy consumption, and simplicity of hardware and software implementations [1], [2], [3]. Over the past few decades, numerous studies have been conducted to investigate thinned array design and optimization. For instance, a probabilistic approach to arrays with randomly spaced elements was proposed in [4]. Thinned arrays designed with statistical methods were presented in [5], and aperture optimization techniques using genetic algorithms were shown in [6], [7], and [8]. Fig. 1.

Element configurations of (a) circular aperture as a reference, 50% filled spiral array, and 50% filled diffused-thinned array, all mapped into a 1024-element () square array. The dark cells indicate turned-on elements and the blue cells indicate turned-off elements. Simulated azimuth plane patterns at (b) broadside and (c) −60° scan angle. Simulated elevation plane patterns at (d) broadside and (e) −60° scan angle. The amplitudes are given in normalized decibel scale for each pattern.