Radio frequency doubler and tripler

1. A radiofrequency doubler comprising:

a first transistor and a second transistor connected in parallel between a first differential output and a first terminal of a current source configured to provide a bias current, a second terminal of the current source being connected to a first supply potential;

a third transistor connected between the first terminal of the current source and a second differential output;

a circuit configured to:

apply an AC component of a first differential input and a first DC voltage to a gate of the first transistor,

apply an AC component of a second differential input and the first DC voltage to a gate of the second transistor, and

apply a second DC voltage to a gate of the third transistor; and

a feedback loop configured to control the first voltage or the second voltage from a difference between DC components of the first and second differential outputs so as to equalize the DC components.

2. The radiofrequency doubler of claim 1 , wherein the feedback loop is configured to provide an output voltage representative of the difference.

3. The radiofrequency doubler of claim 2 , wherein the feedback loop comprises a first input connected to the first differential output, a second input connected to the second differential output and an output configured to provide the output voltage.

4. The radiofrequency doubler of claim 3 , wherein the feedback loop comprises:

an operational amplifier;

a first capacitor connected between a non-inverting input of the amplifier and the first supply potential;

a second capacitor connected between an inverting input of the amplifier and an output of the amplifier;

a first resistor coupling the non-inverting input to the first input of the feedback loop when the first voltage is controlled by the feedback loop or to the second input of the feedback loop when the second voltage is controlled by the feedback loop; and

a second resistor coupling the inverting input to the second input of the feedback loop when the first voltage is controlled by the feedback loop or to the second input of the feedback loop when the second voltage is controlled by the feedback loop.

5. The radiofrequency doubler of claim 2 , wherein the circuit is configured to provide the first voltage from the output voltage of the feedback loop when the first voltage is controlled by the feedback loop or to provide the second voltage from the output voltage of the feedback loop when the second voltage is controlled by the feedback loop.

6. The radiofrequency doubler of claim 5 , wherein the circuit comprises an output connected to the gate of the third transistor, the output being configured to provide the output voltage of the feedback loop when the second voltage is controlled by the feedback loop or a constant bias voltage when the first voltage is controlled by the feedback loop.

7. The radiofrequency doubler of claim 6 , wherein the circuit comprises:

a third capacitor coupling the first differential input to the gate of the first transistor;

a fourth capacitor coupling the second differential input to the gate of the second transistor;

a third resistor coupling the gate of the first transistor to a first node configured to receive the output voltage of the feedback loop when the first voltage is controlled by the loop or the bias voltage when the second voltage is controlled by the loop;

a fourth resistor coupling the gate of the second transistor to the first node; and

a fifth capacitor coupling the first node to the first supply potential.

8. The radiofrequency doubler of claim 6 , wherein the circuit comprises a transformer having its primary coil coupled to the first and second differential inputs and its secondary coil coupled to the gates of the first and second transistors, the secondary coil being configured to be biased by the output voltage of the feedback loop when the first voltage is controlled by the loop or by the bias voltage when the second voltage is controlled by the loop.

9. The radiofrequency doubler of claim 6 , wherein the circuit comprises a sixth capacitor coupling the output of the circuit to the first supply potential.

10. The radiofrequency doubler of claim 2 , wherein the circuit is configured to receive the output voltage of the feedback loop.

11. The radiofrequency doubler of claim 1 , wherein the first supply potential is ground.

12. A radiofrequency tripler comprising:

a first transistor and a second transistor connected in parallel between a first differential output and a first terminal of a current source configured to provide a bias current, a second terminal of the current source being connected to a first supply potential;

a third transistor connected between the first terminal of the current source and a second differential output;

a circuit configured to:

apply an AC component of a first differential input and a first DC voltage to a gate of the first transistor,

apply an AC component of a second differential input and the first DC voltage to a gate of the second transistor, and

apply a second DC voltage to a gate of the third transistor;

a feedback loop configured to control the first voltage or the second voltage from a difference between DC components of the first and second differential outputs so as to equalize the DC components; and

a radiofrequency mixer configured to mix a first radiofrequency signal and a second radiofrequency signal, the radiofrequency mixer comprising a first pair of differential inputs configured to receive the first signal, and a second pair of differential inputs configured to receive the second signal,

wherein the first pair of differential inputs is connected to the first and second differential inputs of a radiofrequency doubler, and the second pair of differential inputs is connected to the first and second differential outputs of the radiofrequency doubler.

13. The radiofrequency tripler of claim 12 , wherein the radiofrequency mixer comprises:

a fourth transistor connected between a first input of the second pair of inputs and a first differential output of the radiofrequency tripler;

a fifth transistor connected between the first input of the second pair of inputs and a second differential output of the radiofrequency tripler;

a sixth transistor connected between a second input of the second pair of inputs and the first output of the radiofrequency tripler; and

a seventh transistor connected between the second input of the second pair of inputs and the second output of the radiofrequency tripler.

14. The radiofrequency tripler of claim 13 ,

wherein a first input of the first pair of differential inputs is connected to a gate of the fourth transistor and to a gate of the seventh transistor, and

wherein a second input of the first pair of differential inputs is connected to a gate of the fifth transistor and to a gate of the seventh transistor.

15. The radiofrequency tripler of claim 12 , wherein the mixer comprises a differential load coupled between the first and second differential outputs of the radiofrequency tripler.

16. The radiofrequency tripler of claim 15 , wherein the differential load comprises:

a seventh capacitor connected between the first and second differential outputs of the radiofrequency tripler;

a first inductor connected between the first differential output of the radiofrequency tripler and a node configured to receive a second supply potential; and

a second inductor connected between the second differential output of the radiofrequency tripler and the node.

17. The radiofrequency tripler of claim 15 , wherein the differential load is tuned to a frequency equal to three times a frequency of the first radiofrequency signal.

18. The radiofrequency tripler of claim 12 , wherein the first supply potential is ground.