Apparatus and method for dynamic DC offset detection and cancellation
AssigneeOrion Microelectronics Corporation
InventorSining Zhou
Life of this patent
Estimating the term…
Abstract
A fixed impedance in parallel with a variable impedance form a high pass filter with a capacitor. An input signal is provided to the capacitor. The value of the variable impedance is controlled in relation to the magnitude of a dynamic DC offset in the input signal to control the corner frequency of the high pass filter, providing a higher corner frequency and more rapid suppression of dynamic DC offset for larger dynamic DC offset magnitudes.
Claims21
A circuit for suppressing dynamic DC offset, comprising:
- a capacitor receiving an input signal;
- a fixed impedance forming a high pass filter with the capacitor;
- a variable impedance in parallel with the fixed impedance;
- and
- a control circuit controlling the value of the variable impedance in correspondence with the value of a dynamic DC offset in the input signal to control the corner frequency of the high pass filter in response to the magnitude of the dynamic DC offset.
A circuit for suppressing dynamic DC offset in a differential signal, comprising:
- a first capacitor receiving an input signal;
- a second capacitor receiving a complementary input signal;
- a first fixed impedance in parallel with a first variable impedance and forming a high pass filter with the first capacitor;
- a second fixed impedance in parallel with a second variable impedance and forming a high pass filter with the second capacitor;
- a control circuit controlling the impedance value of the first and second variable impedances in correspondence with the value of a dynamic DC offset in either of the input signal and the complementary input signal to control the corner frequencies of the high pass filters in response to the magnitude of the dynamic DC offset.
A method for suppressing dynamic DC offset in a signal, comprising:
- providing the signal as input to a high pass filter comprised of a capacitor, a fixed impedance, and a variable impedance in parallel with the fixed impedance;
- and
- controlling the variable impedance to increase the corner frequency of the high pass filter in response to an increase in the magnitude of a dynamic DC offset in the signal.
A receiver circuit comprising:
- at least one mixer for downconverting an input signal;
- and
- a DC offset cancellation circuit for suppressing dynamic DC offset in the downconverted signal, the DC offset cancellation circuit comprising:
- a capacitor receiving the downconverted signal;
- a fixed impedance forming a high pass filter with the capacitor;
- a variable impedance in parallel with the fixed impedance;
- and
- a control circuit controlling the value of the variable impedance in correspondence with the value of dynamic DC offset in the downconverted signal to control the corner frequency of the high pass filter in response to the magnitude of the dynamic DC offset.
Dependencies are inferred from the claim text.