Chapter List

1.1 Introduction

Direction finding (DF) is a procedure for determining the bearing of a transmitting source by observing the direction of arrival, along with other properties of the signal [1]. A direction finding system consists of the components shown in Figure 1.1. The first component of the DF system, the antenna arrays, is described in this chapter. Any errors introduced by the antenna propagate through the rest of the system. Errors introduced by the antenna correspond to unwanted amplitude and phase components in the signals, which cause the phase center of the antenna to move. The antenna phase center is the point at which the radiation from the antenna appears to emanate, if it were transmitting. A change in the phase center corresponds to a change in the coherent summation of the signals from the antenna elements. When processed, these components cause an error in the display output. Errors introduced by the antenna include geometrical placement error, cross-polarization, noise, mutual coupling, multipath, and manufacturing tolerances. Important DF antenna properties include gain, sidelobe level, frequency of operation, polarization, bandwidth, and size.

Figure 1.1: Block diagram of a DF system.

Directivity of the antenna is an important indicator of the antenna s ability to isolate the location of a transmitting signal. Directivity is inversely proportional to the antenna s beamwidth, and the...