A 2.59-GHz RF self-interference cancellation circuit with wide dynamic range for in-band full-duplex radio

A 2.59GHz self-interference cancellation (SIC) circuit is presented for in-band full-duplex radio. The SIC circuit is based on an analog vector modulator whose output can automatically track the time-varying self-interference signal through an analog LMS algorithm based weight calculation circuit. By adding a variable gain stage after the vector modulator, the total dynamic range is significantly widened so that the SIC can deal with large Tx power variation and/or Tx-to-Rx attenuation. Implemented in 16.4 × 11.9 cm
²
printed circuit board, the circuit achieves the cancellation ratio of 39.2 dB and 39.4 dB for 5MHz and 10MHz bandwidth 16-QAM signal, respectively. Also, the dynamic range is increased from 22 dB to 40 dB by properly setting the variable gain.