Cancellation of undesired portions of audio signals

• US 20070002972A1
• Filed: 09/30/2005
• Published: 01/04/2007
• Est. Priority Date: 06/30/2005
• Status: Active Grant

• Current Assignee: Skyworks Solutions Incorporated
• Original Assignee: Silicon Laboratories Incorporated
• Inventors: Taipale, Dana
• Granted Patent: US 8,559,570 B2
• Time in Patent Office: Days
• US Class Current: 375/320
• CPC Class Codes: H04B 1/123 using adaptive balancing or compensation means adaptive filter circuits and algorithms H03H
• CPC Class Codes: H04B 1/28 the receiver comprising at least one semiconductor device having three or more electrodes

Abstract

In one embodiment, the present invention includes a method for determining when a step change occurs to a control value for a numerically controlled oscillator (NCO) providing a mixing signal, mixing the mixing signal with an input radio frequency (RF) signal to obtain an intermediate frequency (IF) signal and demodulating the IF signal into a demodulated signal, generating a correction value based on the step change, and applying the correction value to the demodulated signal. Other embodiments may be used to cancel other undesired signal portions, such as impulse spikes generated from the NCO change.

Claims

1. A method comprising:

determining when a step change occurs to a control value for a numerically controlled oscillator (NCO) providing a mixing signal;

mixing the mixing signal with an input radio frequency (RF) signal to obtain an intermediate frequency (IF) signal and demodulating the IF signal into a demodulated signal;

generating a correction value based on the step change; and

applying the correction value to the demodulated signal.

2. The method of claim 1, further comprising filtering the demodulated signal prior to applying the correction value.

3. The method of claim 2, wherein generating the correction value comprises applying the step change to a response of a filter.

4. The method of claim 1, wherein generating the correction value comprises multiplying a frequency change of the mixing signal caused by the step change by a scaled value.

5. The method of claim 4, wherein the scaled value comprises a demodulator gain.

6. The method of claim 1, further comprising decaying the correction value by a predetermined amount.

7. The method of claim 1, further comprising generating the step change according to an automatic frequency control algorithm.

8. The method of claim 1, further comprising canceling a change in the demodulated signal caused by the step change via the correction value.

9. A method comprising:

determining when a step change occurs to a control value for a numerically controlled oscillator (NCO) providing a mixing signal to an input radio frequency (RF) signal; and

repeating at least one prior demodulated sample generated from the input RF signal when the step change occurs.

10. The method of claim 9, wherein repeating the at least one prior demodulated sample cancels an impulse generated in a demodulator upon the step change.

11. The method of claim 9, wherein repeating the at least one prior demodulated sample comprises outputting at least one delayed demodulator sample to an output signal path upon occurrence of the step change.

12. The method of claim 11, further comprising thereafter outputting a current demodulated sample to the output signal path.

13. An apparatus comprising:

a digital signal processor (DSP) to generate a demodulated signal-based on an intermediate frequency (IF) signal obtained from an incoming radio frequency (RF) signal mixed with a controlled oscillator frequency signal; and

a cancellation circuit to cancel a portion of the demodulated signal caused by a change in the controlled oscillator frequency signal.

14. The apparatus of claim 13, wherein the cancellation circuit is to insert a step change correction into the demodulated signal.

15. The apparatus of claim 13, wherein the cancellation circuit is to repeat at least one demodulated sample to avoid the portion of the demodulated signal.

16. The apparatus of claim 15, wherein the at least one repeated demodulated signal is to be switched into an output line coupled to the DSP.

17. The apparatus of claim 13, wherein the cancellation circuit comprises a portion of the digital signal processor.

18. The apparatus of claim 13, wherein the cancellation circuit is to interpolate a first sample generated before the change in the controlled oscillator frequency and a second sample generated after the change in the controlled oscillator frequency.

19. The apparatus of claim 18, wherein the cancellation circuit is to insert the interpolated value into the demodulated signal.

20. The apparatus of claim 13, wherein the cancellation circuit is to generate a set of interpolated values to insert into the demodulated signal.

21. The apparatus of claim 13, further comprising a switch to couple the cancellation circuit to an output line after the change in the controlled oscillator frequency.

22. A system comprising:

a mixer to mix an incoming radio frequency (RF) signal with a controlled oscillator frequency to obtain an intermediate frequency (IF) signal;

a controlled oscillator to generate the controlled oscillator frequency;

a digital signal processor (DSP) to generate a demodulated signal based on the IF signal; and

a correction circuit to impart a correction to an undesired impulse within the demodulated signal caused by a change in the controlled oscillator frequency.

23. The system of claim 22, wherein the correction circuit is to generate an image of the undesired impulse and to transmit the image to an output of the DSP.

24. The system of claim 22, wherein the correction circuit is to store samples of the demodulated signal and to couple at least one of the samples to an output of the DSP in place of the undesired impulse.

25. The system of claim 22, wherein the controlled oscillator, the mixer and the DSP are integrated in a single substrate.