Band Blocking Filter for Attenuating Unwanted Frequency Components

A band blocking filter comprising first and second stages, each stage comprising:

• an input port that receives an input signal having a plurality of frequency components including a first frequency component at a frequency of fb characterized by an amplitude, A, and phase and a second frequency component having a frequency of fg;
• a cancellation signal generator that generates a cancellation signal having a frequency of fb and an amplitude and phase determined by said first frequency component;
• and
• a combining circuit having a signal input that receives said input signal and a cancellation signal input that receives said cancellation signal, said combining circuit combining said cancellation signal with said input signal to generate an output signal on a combining circuit output line, said output signal having said second frequency component and a residual signal at frequency fb having an amplitude less than A,
• wherein said input port of said second stage receiving said output signal from said subtractor circuit in said first stage.