Reduction of second order distortion in real time

1. In a radio receiver, a method of reducing second order distortion components, comprising:

at a first mixer, mixing an input signal with an oscillator signal to generate an I component of a received radio signal;

at a second mixer, mixing the input signal with a phase shifted oscillator signal to generate a Q component of the received radio signal;

where the I and Q components of the received signal have a receive bandwidth;

computing an estimate of second order distortion components as a power output of the I and Q components between approximately the receive bandwidth and twice the receive bandwidth of the received radio signals; and

adjusting an operational parameter of the radio receiver to reduce the estimated value of second order distortion components.

2. The method in accordance with claim 1 , where the operational parameter of the radio receiver comprises an operational parameter of one or both of the first and second mixers.

3. The method in accordance with claim 1 , where the operational parameter of the radio receiver comprises bias levels of one or both of the first and second mixers.

4. The method in accordance with claim 3 , where the bias level comprises a gate bias voltage of one or both of the first and second mixers.

5. The method in accordance with claim 3 , where the bias level comprises a bulk bias voltage of one or both of the first and second mixers.

6. The method in accordance with claim 1 , where the operational parameter of the radio receiver comprises an operational parameter of a filter.

7. The method in accordance with claim 6 , where the operational parameter of the filter comprises a filter Q or bandwidth.

8. The method in accordance with claim 6 , where the operational parameter of the filter comprises a notch frequency.

9. A radio receiver, comprising:

a local oscillator;

a first mixer, configured to mix an input signal with a local oscillator signal from the local oscillator to generate an I component of a received radio signal;

a second mixer, configured to mix the input signal with a phase shifted local oscillator signal to generate a Q component of the received radio signal;

where the I and Q components of the received signal have a receive bandwidth;

a processor programmed to:

compute an estimate of second order distortion components as a power of the I and Q components between approximately the receive bandwidth and twice the receive bandwidth of the received radio signals; and

adjust an operational parameter of the radio receiver to reduce the estimate of second order distortion components.

10. The radio receiver in accordance with claim 9 , where the operational parameter of the radio receiver comprises an operational parameter of one or both of the first and second mixers.

11. The radio receiver in accordance with claim 9 , where the operational parameter of the radio receiver comprises bias levels of one or both of the first and second mixers.

12. The radio receiver in accordance with claim 11 , where the bias level comprises a gate bias voltage of one or both of the first and second mixers.

13. The radio receiver in accordance with claim 11 , where the bias level comprises a bulk bias voltage of one or both of the first and second mixers.

14. The radio receiver in accordance with claim 11 , further comprising one or more digital to analog converters coupled to the processor and configured to convert digital control signals from the processor to a voltage that sets a bias level of one or both of the first and second mixers.

15. The radio receiver in accordance with claim 11 , further comprising one or more digital to analog converters coupled to the processor and configured to convert digital control signals from the processor to a voltage that sets a gate or a bulk bias of one or both of the first and second mixers.

16. The radio receiver in accordance with claim 9 , where the operational parameter of the radio receiver comprises an operational parameter of a filter.

17. The radio receiver in accordance with claim 16 , where the operational parameter of the filter comprises a filter Q or bandwidth.

18. The radio receiver in accordance with claim 16 , where the operational parameter of the filter comprises a filter notch frequency.

19. A radio receiver, comprising:

a local oscillator;

a first mixer, configured to mix an input signal with a local oscillator signal from the local oscillator to generate an I component of a received radio signal;

a second mixer, configured to mix the input signal with a phase shifted local oscillator signal to generate a Q component of the received radio signal;

where the I and Q components of the received signal have a receive bandwidth;

a programmed processor;

one or more digital to analog converters coupled to the processor and configured to convert digital control signals from the processor to a voltage that sets a bias level of one or both of the first and second mixers;

where the processor is programmed to:

compute an estimate of second order distortion components as a power output of the I and Q components between approximately the receive bandwidth and twice the receive bandwidth of the received radio signals; and

adjust an operational parameter of the radio receiver to reduce the estimate of second order distortion components.

20. The radio receiver in accordance with claim 19 , where the bias level comprises a gate or bulk bias.