Passive Feed Network Designs for Microfluidic Beam-Scanning Focal Plane Arrays and Their Performance Evaluation

Microfluidic focal plane arrays (MFPAs) have been recently introduced to implement compact high-gain beam-scanning antennas without resorting to active RF devices. This beam-scanning technique relies on a patch antenna element that can be microfluidically repositioned at the focal plane of a microwave lens. The feed network is strategically designed to be passive and accommodate the position variation in the antenna element. This paper, for the first time, considers the design details and performance evaluation of three different passive network layouts that can potentially be utilized to excite MFPAs. Specifically, resonant corporate, resonant straight, and nonresonant straight microstrip line feed networks are introduced and their loss/bandwidth performances are investigated using the transmission line theory. In addition, a method of moments and ray tracing-based hybrid analysis is utilized to demonstrate the impact of the proposed feed networks on the radiation properties of the MFPA in terms of realized gain and side lobe levels (SLLs). It is shown that the resonant and nonresonant straight microstrip line feed networks reduce the SLL by more than 10 dB relative to the resonant corporate feed network utilized in the prior work. The performance improvements are experimentally verified through an eight-element extended hemispherical dielectric lens-based MFPA prototype. Different than the recent work that relied on liquid metal, the antenna element of this MFPA is implemented from a metalized plate by carrying out flow characterizations on various microfluidic channel geometries. This metalized plate approach paves the way for reliable liquid-metal-free microfluidic reconfigurable devices with higher efficiency and power-handling capabilities.