A Pseudo-Doppler direction finding antenna system was designed with four dipoles vertically arrayed around a circle. This paper presents an overview of the impedance matching techniques for the designed dipole antenna array.
The operating frequency range is so wide, from 20 MHz to 175 MHz, that it is very difficult to achieve good impedance matching for dipole array. A main idea for solving this problem is based on a lossy matching scheme. The first step is to reduce the sharp resonance of dipole antenna by inserting a resistance component into each dipole. And next, wideband low loss impedance transformation is utilized to achieve a desired impedance matching.
All of these procedures are described by using Smith Chart in graphical presentation, and the Voltage Standing Wave Ratio was measured to be maintained below 3 to 1 over all operating frequency range.
