Apparatus comprising a local oscillator for driving a mixer
An apparatus comprising a local oscillator (LO) for driving a mixer, the LO being configured to oscillate at an oscillation frequency, and generate a first set of LO signals, wherein each of the first set of LO signals has a LO signal frequency equal to a first multiplication factor m multiplied by the oscillation frequency, the first multiplication factor m, being an integer greater than or equal to two, and each of the first set of LO signals is separated by adjacent LO signals by a phase difference equal to 360° divided by a first variable n, the first variable n being an integer that is greater than or equal to two.
1. An apparatus comprising a local oscillator (LO) for driving a mixer, the LO being configured to:
oscillate at an oscillation frequency; and
generate a first set of LO signals; wherein:
each of the first set of LO signals has a LO signal frequency equal to a first multiplication factor m multiplied by the oscillation frequency, the first multiplication factor m, being an integer greater than or equal to two; and
each of the first set of LO signals is separated by adjacent LO signals by a phase difference equal to 360° divided by a first variable n, the first variable n being an integer that is greater than or equal to two; and wherein
the LO comprises a plurality of frequency multiplication circuits for generating the first set of LO signals,
whereby the apparatus further comprises a buffer circuit, the mixer configured to receive the first set of LO signals via the buffer circuit.
2. The apparatus of claim 1 , wherein the LO comprises a ring oscillator oscillating at the oscillation frequency.
3. The apparatus of claim 2 , wherein the ring oscillator comprises a plurality of stages equal to an integer k multiplied by the first variable n multiplied by the first multiplication factor m, where the integer k is greater than or equal to one.
4. The apparatus of claim 3 , wherein each stage comprises an inverter comprising:
an input coupled to an output of an inverter of the previous stage; and
comprising an output coupled to an input of an inverter of the next stage.
5. The apparatus of claim 4 , wherein each inverter of each stage is configured to generate a ring oscillator signal that is separated by the ring oscillator signals of adjacent stages by a phase difference equal to a fraction having a numerator of 360° and a denominator of n multiplied by m.
6. The apparatus of claim 5 , wherein each frequency multiplication circuit is configured to receive a subset of the ring oscillator signals, where the subset of the ring oscillator signals are different from those received by each additional frequency multiplication circuit and the subset of ring oscillator signals are separated by adjacent ring oscillator signals within the subset by a phase difference equal to 360° divided by n.
7. The apparatus of claim 6 , wherein each frequency multiplication circuit is configured to generate one of the first set of LO signals using the subset of the ring oscillator signals received by said frequency multiplication circuit.
8. The apparatus of claim 7 , wherein each frequency multiplication circuit is configured to generate a LO signal in a high state when n+1/2 of the ring oscillator signals received by said frequency multiplication circuit are simultaneously in a high state, otherwise said frequency multiplication circuit is configured to generate a LO signal in a low state.
9. The apparatus of claim 1 , wherein n is equal to three, such that each of the first set of LO signals is separated by adjacent LO signals by a phase difference equal to 120°.
10. The apparatus of claim 9 , wherein the LO comprises a ring oscillator oscillating at the oscillation frequency and the ring oscillator comprises nine stages.
11. The apparatus of claim 1 , comprising the mixer, wherein the mixer comprises at least n switches, wherein each LO signal is provided to one of the switches.
12. The apparatus of claim 1 , wherein the LO is configured to generate a second set of LO signals, wherein each of the second set of LO signals has a LO signal frequency equal to the first multiplication factor m multiplied by the oscillation frequency, each of the second set of LO signals is separated by adjacent LO signals within the second set by a phase difference equal to 360° divided by the first variable n, and each of the second set of LO signals has a phase difference of 180° divided by the first variable n when compared with a corresponding LO signal within the first set of LO signals.
13. The apparatus of claim 12 , wherein the mixer is a differential mixer.
14. The apparatus of claim 1 , wherein the duty cycle of each of the LO signals of the first set of LO signals comprises the nth harmonic of the oscillation frequency in its Fourier Series.
15. The apparatus of claim 1 comprising an image frequency rejection circuit comprising the local oscillator and the mixer.
16. The apparatus of claim 15 , wherein the image frequency rejection circuit comprises at least one additional local oscillator for driving an additional mixer, the additional LO being configured to operate at a second oscillation frequency and generate a first additional set of LO signals; wherein each of the first set of additional LO signals has a LO signal frequency equal to a second multiplication factor h multiplied by the second oscillation frequency, the second multiplication factor h being an integer greater than or equal to two; and each of the first set of additional LO signals is separated by adjacent LO signals by a phase difference equal to 360° divided by the first variable n.
17. The apparatus of claim 15 , wherein the image frequency rejection circuit is configured to enhance interference rejection.
18. The apparatus of claim 15 , wherein the apparatus is configured to down-convert or up-convert an RF signal with an n-th harmonic of the LO signal frequency, the first variable being equal to n, the RF signal being in the middle of two advertising channels.
19. The apparatus of claim 15 , wherein, the LO is configured to:
generate a second set of LO signals, wherein each of the second set of LO signals has a LO signal frequency equal to the first multiplication factor m multiplied by the oscillation frequency, each of the second set of LO signals is separated by adjacent LO signals within the second set by a phase difference equal to 360° divided by the first variable n, and each of the second set of LO signals has a phase difference of 180° divided by the first variable n when compared with a corresponding LO signal within the first set of LO signals;
generate a third set of LO signals, wherein each of the third set of LO signals has a LO signal frequency equal to the first multiplication factor multiplied by the oscillation frequency, each of the third set of LO signals is separated by adjacent LO signals within the third set by a phase difference equal to 360° divided by the first variable, and each of the third set of LO signals has a phase difference of 90° divided by the first variable when compared with a corresponding LO signal within the second set of LO signals; and
generate a fourth set of LO signals, wherein each of the fourth set of LO signals has a LO signal frequency equal to of the first multiplication factor multiplied by the oscillation frequency, each of the fourth set of LO signals is separated by adjacent LO signals within the fourth set by a phase difference equal to 360° divided by the first variable, and each of the fourth set of LO signals has a phase difference of 90° divided by the first variable when compared with a corresponding LO signal within the first set of LO signals.
20. A method of operating an apparatus comprising a local oscillator (LO) for driving a mixer, the LO oscillates at an oscillation frequency, the method comprising generating a first set of LO signals using the LO, wherein each of the first set of LO signals has a LO signal frequency equal to a first multiplication factor m multiplied by the oscillation frequency, the first multiplication factor m being an integer greater than or equal to two, and each of the first set of LO signals is separated by adjacent LO signals by a phase difference equal to 360° divided by a first variable n, the first variable n being an integer that is greater than or equal to two; and wherein
the LO comprises a plurality of frequency multiplication circuits for generating the first set of LO signals, the first set of LO signals being received by the mixer via a buffer circuit.
21. An apparatus comprising a local oscillator (LO) for driving a mixer, the LO being configured to:
oscillate at an oscillation frequency; and
generate a first set of LO signals; wherein:
each of the first set of LO signals has a LO signal frequency equal to a first multiplication factor m multiplied by the oscillation frequency, the first multiplication factor m, being an integer greater than or equal to two; and
each of the first set of LO signals is separated by adjacent LO signals by a phase difference equal to 360° divided by a first variable n, the first variable n being an integer that is greater than or equal to two; wherein
the LO is configured to generate a second set of LO signals, wherein each of the second set of LO signals has a LO signal frequency equal to the first multiplication factor m multiplied by the oscillation frequency, each of the second set of LO signals is separated by adjacent LO signals within the second set by a phase difference equal to 360° divided by the first variable n, and each of the second set of LO signals has a phase difference of 180° divided by the first variable n when compared with a corresponding LO signal within the first set of LO signals,
whereby the apparatus further comprises a buffer circuit, the mixer configured to receive the first set of LO signals and the second set of LO signals via the buffer circuit.
22. The apparatus of claim 21 , wherein the mixer is a differential mixer.