Frequency agile bandstop filter (FABSF)

Abstract

The frequency agile bandstop filter (FABSF) is an RF system component that functions as a frequency agile tunable notch filter capable of rejecting the low-level noise in presence of a high-level signal such as the out-of-band noise at the output of a high-power amplifier.The FABSF finds application in a frequency agile duplexer (FAD) system architecture to be implemented in the RF front-end of frequency division duplex (FDD) radio.Index Terms -Flexible radio, base station, tunable filter, feedforward cancellation, frequency agile duplexer.

Hybrid RF-digital feed-forward filter for high-order frequency agile filtering

“…A system with two FF cancellation loops was reported in [28] to improve duplexer isolation in a BTS. This system is located at the output of the TX chain, and is designed to cancel noise generated by the transmitter in the RX band.…”

“…This measurement is used to manually tune the control signals.The band used in this work was at 1900 MHz. Simulation results showed 32 dB of attenuation in the error cancellation loop over a 5 MHz RX channel with an FDD separation of 5 MHz[28]. The signal cancellation loop attenuation was greater than 2033 dB over the TX channel.…”

“…The error cancellation loop attenuation corresponds to the improvement in duplexer isolation over the RX channel. Frequency agile BSF schematic[28]…”