This paper describes a cavity-backed patch-antenna geometry, which features multiple dielectric layers and shorting posts. These features are exploited to design antennas which retain many of the desirable characteristics of conventional microstrip antennas, yet overcome some of their inherent disadvantages.
Introductionue to their many desirable characteristics, microstrip antennas D are used widely in UHF, microwave, and millimeter-wave applications. However, utilization of these antennas, in many applications, is hampered by certain inherent disadvantages. Among the most serious of these limitations are poor scan performance in an array environment, low gain, limited polarization diversity, lack of frequency agility, and narrow impedance bandwidth. Through certain straightforward design modifications, one or more of these disadvantages can be overcome. The multi-layer, multi-probe cavitybacked patch antenna, shown in Figure 1, provides a great deal of design flexibility, which can be used to enhance the electrical characteristics of patch antennas. Specifically, cavity backing can be used to suppress guided-wave effects, resulting in enhanced impedance bandwidth and scan performance. Shorting posts (or switching diodes) can be used to provide polarization diversity, frequency agility, and bandwidth enhancement. Additional dielectric layers can be used to achieve frequency agility and gain enhancement, and for beam forming. It should be noted that some of the techniques described in this paper are topics of current research. Furthermore, the antenna designer should be aware that the enhancement of one antenna characteristic is often accompanied by a degradation in one or more of its other properties. Here, we attempt to assess each technique, and to mention any disadvantages of which we are aware.
Cavity-backed patch antennasCavity-backed patch antennas have become a focus of interest in recent years [l-41. This interest is due to many attractive features provided by these structures, most notably improved isolation of the radiating element from the rest of the system, enhanced mechanical and thermal performance, and the reduction of guidedwave effects. As a result, these antennas exhibit many desirable characteristics in a phased array. Furthermore, in many practical applications, the antenna structure is embedded in the body of a platform, effectively creating a cavity structure around it. / \ -Probe Feed Shorting Pin L Figure 1. The geometry of a multi-layer, multi-probe cavitybacked patch anteniia.
Computer modelA suitable design, based on the structure shown in Figure 1, is achieved for a specific application by varying its parameters until the design goals are met. This process is prohibitively expensive, if conducted using an iterative hardware-design approach, even if a systematic technique, such as Design Of Experiment (DOE), is implemented. Thus, an accurate and eficient numerical approach is extremely desirable.The numerical techniques used to analyze radiating structures may be classified as...
