I. Introduction
Next generation X-band electronically scanned phased arrays (ESPAs) aim to reduce both deployment and operational expenses by employing scalable, lightweight arrays assembled using low-cost, monolithically integrated transmit/receive (T/R) modules [1]. ESPAs are an integral part of space-based radar systems and are typically realized with the hybrid connection of four discrete components including: feed networks (transmission lines and power dividers), phase shifters, antennas and T/R modules. Current multi-layer T/R module technology has a distinct disadvantage of having a depth larger than its lateral size, preventing its implementation in conformal phased arrays. RF MEMS technology enables the monolithic integration of the ESPA components into one module, thereby enhancing ESPA designs by significantly reducing size, fabrication cost and interconnection losses. Therefore, current phased array technology needs to be redeveloped to increase performance with the necessary cutback in cost and size. Considerable research and development of three-dimensional multilayer technology and the implementation of MEMS technology in ESPAs has been conducted [2]–[6]. Low Temperature Co-fired Ceramics (LTCC) is used in [3] for ESPA component integration, however, LTCC exhibits inherent feature size limitations and high cost. A four-element MEMS array was monolithically integrated in an in-line architecture arrangement on high resistivity silicon (HRS) substrate in [4].