Patent ID: 6980787

Claim:
An apparatus for canceling an image signal from a received radio frequency signal, the apparatus comprising: a ring oscillator for producing a radio frequency signal having in-phase and quadrature phase components, said ring oscillator including a plurality of delay cells, an output of each delay cell being coupled to an input of another delay cell, one of the couplings between delay cells being cross-coupled so that the output of one delay cell is inverted prior to input into another delay cell; a first mixer having inputs configured to receive the in-phase component and the received radio frequency signal and outputting an in-phase signal; a second mixer having inputs configured to receive the quadrature phase component and the received radio frequency signal and outputting a quadrature phase signal; a phase shift device coupled with one of said mixers for receiving an output of said one mixer and outputting a phase shifted signal; and a combiner, coupled to the other of said mixers and said phase shift device without a level shift or inverter circuit, for producing an image cancelled signal; and wherein each of the delay cells comprises gates of two serially connected MOSFETs used for bias and frequency control of that delay cell, gates of two MOSFETs used for an input of that delay cell and drains of two MOSFETs forming the output of the delay cell, the output of the delay cell is delayed by forty-five degrees from the input of the delay cell.