CITY UNIVERSITY OF HONG KONG 香港城市大學 Study on Innovative Integrated Power Amplifier/Low Noise Amplifier/Switch for Wireless Application

The front-end transmit/receive switch circuit is one of the essential elements in modern wireless handsets. The main function of the transmit/receive switch is switch the antenna either to the transmitter or the receiver. It must have high isolation in order to avoid the RF-power of the transmitter (PA) turning on the receiver (LNA), resulting in high loss or in the worst case damage. Low insertion loss is also necessary to maintain efficiency for the transmit power amplifier and low noise for the receive low noise amplifier. The RF switch circuits either uses PIN-Diodes or FET based mmics. Normally, silicon PIN-Diode based switches are suited for low cost or narrow band applications, while FET based mmic switches are suited more for higher performance/cost wide band application. For many handsets PIN-diodes and λ/4 transmission line topology is used to form a low cost, single supply switch. However, the main disadvantages of this low cost PIN-diode switch are its large size and narrow bandwidth. So, the research work performed here is to study a new RF switch circuit topology that is low in cost, small in size, and while maintaining a single positive control voltage. The method proposed here eliminates the RF switch in the RF-front end entirely by directly connecting the Power Amplifier with the Low Noise Amplifier. When connected to the antenna it forms a single pole double throw RF-Switch, herein