Multilayer feeding of a microstrip patch sub-array using Parallel-Plate Dielectric Waveguides (PPDW)

摘要

Printed antennas integrated with feed network and active circuitry in a multilayer architecture is the future technology trend [1,2]. This approach would allow integration of antenna elements with complex processing circuitry, maintaining fabricational and functional modularity at different levels, while overcoming some fundamental constraints. Different circuit levels need to be isolated from each other by placing metal planes in between, lending to parallel-plate type circuit environments. Stripline is the metal choice of transmission medium. However, this lends to problem of power leakage from the stripline [3,4], as well as unwanted excitation of parallel plate mode from layer-to-layer circuit transitions that employ feed-through probes or slot coupling [2]. Such problems can often be unavoidable and prohibitively severe, compelling designers to search for possible design modifications or alternate technology. Use of shorting pins or dielectric plugs placed at different locations in the circuit may provide some ad-hoc help for simple cases [5,2], but may not be practical for more complex configurations. Use of parallel-plate dielectric waveguide (PPDW) may be useful an a possible alternative to stripline, which can potentially overcome the basic problems faced by a stripline-type circuit [6]. In addition, the PPDW can provide a lower level of copper loss than a stripline, which can be a critical consideration for large arrays. However, in contrast with a stripline, the PPDW is not a planar guide, but it can be deposited unto a dielectric or semiconductor substrate or may also be fabricated using modem machining. In this paper we present a prototype design and experiment of a microstrip patch sub-array, fed by a PPDW network configured in four layers. The geometry is shown in Fig.1. The results demonstrate that similar multilayer PPDW feed configurations can really be attractive substitutes for printed striplines, providing high efficiency in layer-to-layer coupling, antenna excitation and power distribution.