Active duplexing for Software Defined Radio

Passive filters are implemented via advanced technologies in the form of surface acoustic wave (SAW) and thin film bulk acoustic resonator (FBAR) devices. These not only exhibit low noise and high linearity features, but also have fixed centre frequency and bandwidth, making them inflexible. Adaptive duplexing eliminates the need for switched multiple band reject filters (BRF) by using a cancellation process. The proposed state of the art technique has the potential to reduce the cost and size of the RF frontend. The operation of the system is described and key specifications of the major building blocks are developed. Test bed measurements illustrate the practical implementation of this methodology.