Method and apparatus of an input resistance of a passive mixer to broaden the input matching bandwidth of a common source/gate LNA

1. A method of operating a receiver, comprising:

amplifying an input signal in a Low Noise Amplifier (LNA) coupled to a resonant circuit;

coupling a switched capacitance circuit to the resonant circuit to reduce a quality factor of the resonant circuit comprising:

coupling current from the resonant circuit through a first switch to a first capacitor integrating a first voltage; and

coupling current from the resonant circuit through a second switch to a second capacitor integrating a second voltage;

enabling the first switch with a clock signal;

enabling the second switch with an inverse clock signal;

applying a first voltage to a positive input of a differential amplifier;

applying a second voltage to a negative input of the differential amplifier; and

providing a sum and a difference frequency spectrum between a signal spectrum carried within the current and a frequency of the clock signal.

2. The method of claim 1 , wherein the LNA is configured in a cascode structure.

3. The method of claim 1 , wherein the first switch and the second switch comprise a first mixer.

4. The method of claim 3 , wherein energy from the resonant circuit powers the first mixer.

5. The method of claim 1 , further comprising:

coupling the resonant circuit through a third switch to a third capacitor;

coupling the resonant circuit through a fourth switch to a fourth capacitor;

employing a quadrature clock signal to enable a third switch of a third capacitor coupled to a first input of a second differential amplifier;

employing a quadrature inverse clock signal to enable a fourth switch of a fourth capacitor coupled to a second input of the second differential amplifier; and

providing an output of the second differential amplifier to produce a quadrature sum frequency and a quadrature difference frequency spectrum between the signal spectrum and the quadrature clock signal.

6. The method of claim 5 , wherein the third switch and the fourth switch comprise a second mixer.

7. The method of claim 5 , wherein the LNA is coupled via a coupling capacitor to common nodes of switches in the first mixer and the second mixer.

8. The method of claim 7 , further comprising providing for a voltage divider to provide DC-biasing for the common nodes.

9. The method of claim 5 , wherein a switched capacitor circuit comprising at least one switch in the first mixer and the second mixer is configured to provide a load resistance in parallel with the resonant circuit, wherein the load resistance is configured to increase bandwidth of the LNA.

10. A receiver apparatus, comprising:

a Low Noise Amplifier (LNA) configured to amplify an input signal;

a resonant circuit coupled to the LNA;

a switched capacitance circuit configured to reduce a quality factor of the resonant circuit, the switched capacitance circuit comprising:

a first switch coupling current from the resonant circuit to a first capacitor integrating a first voltage, the first switch enabled with a clock signal; and

a second switch coupling current from the resonant circuit to a second capacitor integrating a second voltage, the second switch enabled with an inverse clock signal; and

a differential amplifier comprising a positive input for receiving the first voltage and a negative input for receiving the second voltage, the differential amplifier providing a sum and a difference frequency spectrum between a signal spectrum carried within the current and a frequency of the clock signal.

11. The receiver apparatus of claim 10 , wherein the LNA is configured in a cascode structure.

12. The receiver apparatus of claim 10 , wherein the first switch and the second switch comprise a first mixer.

13. The receiver apparatus of claim 10 , wherein energy from the resonant circuit powers the first mixer.

14. The receiver apparatus of claim 10 , further comprising:

a third switch coupling the resonant circuit to a third capacitor, the third switch enabled with a quadrature clock signal;

a fourth switch coupling the resonant circuit to a fourth capacitor, the fourth switch enabled with a quadrature inverse clock signal; and

a second differential amplifier comprising a first input coupled to the third capacitor a second input coupled to the fourth capacitor, and an output that produces a quadrature sum frequency and a quadrature difference frequency spectrum between the signal spectrum and the quadrature clock signal.

15. The receiver apparatus of claim 14 , wherein the third switch and the fourth switch comprise a second mixer.

16. The receiver apparatus of claim 14 , wherein the LNA is coupled via a coupling capacitor to common nodes of switches in the first mixer and the second mixer.

17. The receiver apparatus of claim 16 , further comprising a voltage divider configured to provide DC-biasing to the common nodes.

18. The receiver apparatus of claim 14 , wherein a switched capacitor circuit comprising at least one switch in the first mixer and the second mixer is configured to provide a load resistance in parallel with the resonant circuit, wherein the load resistance is configured to increase bandwidth of the LNA.