A Study of Uniformly Excited Linear Phased Array for Wideband Operation

In this paper a simple and intuitive equation is developed for a uniformly excited linear phased array for wideband frequency operation. This equation unifies phase delay, time delay, antenna element spacing, and operating frequency. Most importantly, the equation shows the array pattern can be normalized and multiplied into its final implementation of any frequency. This means existing array factors in use can be applied to a new design at any frequency. The equation is demonstrated with 3 possible real-world applications. The array pattern is first calculated using the expanded wideband equation and then verified using HFSS using a wideband linear tapered slot antenna for each design. In 2 of the examples, calculation and verification are done at 2 different bands to demonstrate the analysis is indeed normalized and can be multiplied into different frequency bands. The last example shows how the equation calculates element spacing to compensate for a squint-free phased array operating in wideband, which is easily achievable with Active Electronically Scanned Arrays (AESA). The equation provides an intuitive understanding of phased array characteristics in wideband, and it simplifies the design process, hopefully paving the way for further development of phased array systems.

I. Introduction

The motivation for this study was the lack of theoretical methods identified in analyzing and designing phased arrays in wideband operation. Phased array applications have since trended from narrowband systems like PAVE PAWS in the 1970s that operate with only 30MHz of bandwidth [1] to modern radar systems that can span several gigahertz such as frequency-modulated continuous-wave (FMCW) radar system. This trend is not unique to the military; civilian applications in communications have also trended from narrowband systems such as GSM services to modern 5G UWB and future 6G systems. Modern micro-location systems also demonstrate wideband characteristics [2], [3]. Wider bandwidth is the evolutionary path for future microwave systems and antenna applications. However, theoretical descriptions for wideband operation are still limited [4].