Clock signal leakage cancellation in wireless systems
View Patent ↗Methods and systems for utilizing undersampling for crystal leakage cancellation are disclosed and may include undersampling a composite signal comprising a desired signal and leakage signals due to one or more clock signals. Measured DC signals generated by each of the undersampled signals may be reduced by adjusting the phase and/or amplitude of the clock signals. The undersampling may be performed at one or more of the one or more clock signals, or at integer sub-harmonics of the clock signals. The composite signal may include a signal received by a wireless system or a signal to be transmitted by the wireless system. The undersampled signals may be low-pass filtered. The desired signal may include in-phase and quadrature signals or a polar signal. The undersampling may be performed by one or more sample and hold circuits and the clock signals may be generated utilizing one or more crystal oscillators.
1. A method for wireless communication in a wireless system, said method comprising:
undersampling a composite signal comprising a desired signal and a leakage signal to isolate the leakage signal from the desired signal, said leakage signal due to a clock signal applied to digital circuitry; and
adjusting said clock signal to reduce said leakage signal relative to said desired signal in said composite signal.
2. The method of claim 1 wherein the undersampling includes undersampling said composite signal at a frequency that is substantially equal to a sub-harmonic frequency of said clock signal.
3. The method of claim 1 wherein the undersampling includes undersampling said composite signal at a frequency that is an integer sub-harmonic of said clock signal.
4. The method of claim 1 , wherein said composite signal is received by said wireless system.
5. The method of claim 1 , wherein said composite signal is transmitted by said wireless system.
6. The method of claim 1 comprising low-pass filtering the composite signal after undersampling to isolate the leakage signal from the desired signal.
7. The method of claim 1 , wherein said desired signal comprises in-phase and quadrature component signals.
8. The method of claim 1 , wherein said leakage signal includes a spurious component from the clock signal.
9. The method of claim 1 wherein the undersampling includes undersampling said composite signal utilizing a sample and hold circuit.
10. The method of claim 1 comprising generating said clock signal utilizing a crystal oscillator.
11. A wireless system comprising:
a circuit that undersamples a composite signal comprising a desired signal and a leakage signal and isolates the leakage signal from the desired signal, said leakage signal due to a clock signal; and
said circuit adjusts said clock signal to reduce said leakage signal relative to said desired signal in said composite signal.
12. The wireless system of claim 11 wherein said circuit undersamples said composite signal at a frequency that is substantially equal to a sub-harmonic of said clock signal.
13. The wireless system of claim 11 wherein said circuit undersamples said composite signal at a frequency that is an integer sub-harmonic of said clock signal.
14. The wireless system of claim 11 , wherein said composite signal is received by said wireless system.
15. The wireless system of claim 11 , wherein said composite signal is transmitted by said wireless system.
16. The wireless system of claim 11 , wherein said circuit comprises a low-pass filter.
17. The wireless system of claim 11 , wherein said desired signal comprises in-phase and quadrature component signals.
18. The wireless system of claim 11 , wherein said leakage signal includes a spurious component from the clock signal.
19. The wireless system of claim 11 , wherein said circuit comprises a sample and hold circuit.
20. The wireless systenl of claim 11 , wherein said clock signal is generated by a crystal oscillator.