An analog adaptive notch filter based on the noise cancellation principle

An analog adaptive notch filter implementation at 54.1 MHz is presented in this paper. The analog circuit is implemented using discrete components. Implementation issues such as components phase shift and DC offset are discussed and solution for them are proposed. In addition, effect of frequency offset between reference and input signal is discussed. The implemented circuit has -3 dB bandwidth of 300 Hz and a null depth of 45 dB or better.