Frequency agile RF feedforward noise cancellation system

Abstract

A frequency agile feedforward noise cancellation system (FFCS) concept was developed to increase the isolation between the transmitter and receiver which share a common antenna in a frequency division duplex (FDD) radio front-end. A cancellation performance of 50 dB was achieved in a bandwidth of 4.5 MHz. The performance was maintained throughout a tuning bandwidth of 25 MHz, centered at 836.5 MHz. The FFCS has applications in communication systems requiring tunable notch filters with wideband performance. The research on the FFCS is aimed at developing technology to complement a cellular base station (BTS) duplexer of reduced order and reduced size and capable of operating in any CDMA cellular bands. The FFCS component is envisioned as enabling technology to implement frequency agile duplexers.