Frequency multiplier

1. A frequency multiplier for generating an output signal having a frequency N times an input signal, with N equal to or greater than 3, the frequency multiplier comprising:

a phase splitter circuit responsive to the input signal for generating N signals with phase differences; and

a mixer circuit responsive to the N signals of the phase splitter circuit configured to mix the N signals using a multiplying function to provide an output signal having a frequency N times the input signal.

2. The frequency multiplier of claim 1 in which the phase splitter circuit includes a quadrature circuit responsive to the input signal for generating I and Q signals and a phasor circuit responsive to the quadrature circuit.

3. The frequency multiplier of claim 2 in which the quadrature circuit includes an R-C polyphase network.

4. The frequency multiplier of claim 2 in which the quadrature circuit includes a distributed quadrature network.

5. The frequency multiplier of claim 4 in which the distributed quadrature network is a Lange coupler.

6. The frequency multiplier of claim 2 in which the phasor circuit includes a transconductance circuit for generating an output current that is linearly proportional to the I or Q signals.

7. The frequency multiplier of claim 6 further including common load resistors for adding the currents from the transconductance circuits to create a predetermined phase.

8. The frequency multiplier of claim 1 in which the difference of phase between the signals is approximately 360°/N.

9. The frequency multiplier of claim 1 in which the difference of phase between the signals is approximately 180°/N.

10. The frequency multiplier of claim 1 in which N=3.

11. The frequency multiplier of claim 10 in which the mixer circuit is a 3 input stacked Gilbert-cell mixer.

12. The frequency multiplier of claim 1 in which N=4 or greater.

13. The frequency multiplier of claim 1 in which the input signal is a differential input signal.

14. The frequency multiplier of claim 1 in which the input signal is a single-ended signal.

15. The frequency multiplier of claim 1 in which N=4 and the mixer circuit includes four levels of transistors to accommodate four balanced inputs.

16. The frequency multiplier of claim 1 in which the mixer circuit includes cascaded mixers.

17. The frequency multiplier of claim 1 in which the mixer circuit multiplies the N signals of the phasor circuit to provide an output signal having a frequency N times the input signal.

18. The frequency multiplier of claim 1 further including amplifier circuits responsive to the phase splitter circuit for amplifying the N signals.

19. The frequency multiplier of claim 18 in which the amplifier circuits convert the N signals from sine waves to square-waves.

20. The frequency multiplier of claim 18 in which the amplifier circuits include a single-stage amplifier to amplify each of the N signals.

21. The frequency multiplier of claim 18 in which the amplifier circuits include two or more amplifier stages to amplify some of the N signals.

22. A frequency multiplier for generating an output signal having a frequency N times an input signal, with N equal to or greater than 3, the frequency multiplier comprising:

a quadrature circuit responsive to the input signal for generating I and Q signals;

a phasor circuit responsive to the quadrature circuit for generating N signals with phase multiples of approximately 360°/N;

amplifier circuits responsive to the phasor circuit for amplifying the N signals; and

a mixer circuit responsive to the N signals of the phase splitter circuit configured to mix the N signals using a multiplying function to provide an output signal having a frequency N times the input signal.

23. A frequency multiplier for generating an output signal having a frequency N times an input signal, with N equal to or greater than 3, the frequency multiplier comprising:

a quadrature circuit responsive to the input signal for generating I and Q signals;

a phasor circuit responsive to the quadrature circuit for generating N signals with phase multiples of approximately 180°/N;

amplifier circuits responsive to the phasor circuit for amplifying the N signals and converting the N signals from sine waves to square-waves; and

a mixer circuit responsive to the amplifier circuits for detecting transitions of the amplified N signals to provide an output signal having a frequency N times the input signal.

24. A method for generating an output signal having a frequency N times the input signal, with N equal to or greater than 3, the method comprising:

generating N signals with phase differences;

mixing the N signals using a multiplying function to provide an output signal having a frequency N times the input signal.

25. The method of claim 24 in which the difference of phase between the signals is approximately 360°/N.

26. The method of claim 24 in which the difference of phase between the signals is approximately 180°/N.

27. A frequency multiplier for generating an output signal having a frequency N times an input signal, with N equal to or greater than 3, the frequency multiplier comprising:

a phase splitter circuit responsive to the input signal for generating N signals with phase differences, the phase splitter circuit including a quadrature circuit having a distributed quadrature network responsive to the input signal for generating I and Q signals and a phasor circuit responsive to the quadrature circuit; and

a mixer circuit responsive to the N signals of the phase splitter circuit configured to mix the N signals using a multiplying function to provide an output signal having a frequency N times the input signal.

28. A frequency multiplier for generating an output signal having a frequency N times a differential input signal, with N equal to or greater than 3, the frequency multiplier comprising:

a phase splitter circuit responsive to the differential input signal for generating N signals with phase differences; and

a mixer circuit responsive to the N signals of the phase splitter circuit for providing an output signal having a frequency N times the differential input signal.