Multilayer R-Card fence design for ground bounce reduction

Multilayer R-Card fences have been designed and evaluated for an outdoor range in order to reduce the ground bounce effects. This design not only can reduce the specular reflection by the ground to the receiving area but also reduce the reflection back to the transmit area due to the corner reflector effects. It has been found from the previous and current studies that tapered R-Card fences can very effectively used in reducing multipath stray signals, such as the ground reflection term in an outdoor range. With available commercial resistive sheets, these fences can be built very inexpensively and has great potential in many other applications.

1. Introduction

One of the major stray signal sources in an outdoor far field measurement range is the multi-path signal caused by the reflection from the ground. The ground bounce signal causes error in the measurement and also significantly reduces the size of test area. Single layer R-Card fences have been designed and implemented [1] in outdoor range to reduce the ground bounce effect and increase the accuracy of the measurement results. It has been shown both theoretically and experimentally that multiple R-Card fences can effectively and significantly reduce the ground bounce reflection. For a single layer design as shown in [1], the major design issue is to reduce the illumination on the ground from the transmit antenna and also attenuate the reflected field to the test area or receiving antenna by using multiple R-Card fences, as shown in Figure 1. With this in mind, each R-Card fence consists of a metal section at the bottom of each fence and gradually changes to tapered resistive distribution as shown in Figure 2 of [1]. The reflected field from the ground will transmit through the adjacent R-Card fence, if exists, such that the field will be further attenuated before it reaches the receiving antenna (or test area). One of the potential problem with this design is that the metal portion of the fence and the ground form a corner reflector that can cause significant reflection back to the transmit antenna as shown in Figure 2. For some applications, this term may not be desirable. This paper briefly describes how one can design a fence with multiple R-Card layers to reduce both the forward and backward ground reflections. Figure 1. Tapered R-Card Fences for ground bounce reduction. Figure 2. Corner reflection effects caused by the intersection of R-Card fence and ground.