Active switch / antenna

Abstract

Modern wireless communication system employs the time division duplex (TDD), it requires the use of duplexer in the form of an RF switch at the front end to switch between transmission and reception mode of operation. Pin diode is commonly used as the switching element in the RF switches in traditional front end design for its small size, low loss and low cost. In this project, a design of a switch/ antenna at the frequency 2.4GHz is presented. The project implementation combines the narrowband low-noise amplifier (LNA), power amplifier (PA) and the square patch antenna. It aims to eliminate the pin diode switch and reduce the antenna size in the front end. In my design, the transmission and reception mode is toggled by biasing the LNA and the PA to their ON/ OFF states, therefore, the pin diode is eliminated. On the other hand, the antenna size is reduced by terminating the LNA in OFF state when transmission or PA in OFF state when reception with low impedance. Its principle looks like as a square patch antenna adding a shorting wall. By applying this technique, around 75% reduction of the physical area of the antenna size can be achieved.