Cancellation of undesired portions of audio signals
AssigneeSilicon Laboratories Inc.
InventorDana Taipale
Life of this patent
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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.
Claims22
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 a timing and magnitude of the step change;
- and
- filtering the demodulated signal prior to applying the correction value to the demodulated signal.
A method comprising:
- mixing a mixing signal with an input radio frequency (RF) signal to obtain a downconverted signal;
- demodulating the downconverted signal to output demodulated samples as an output signal;
- determining when a step change occurs to a control value for a numerically controlled oscillator (NCO) providing the mixing signal to the input RF signal;
- and
- repeating at least one prior demodulated sample generated from the input RF signal as the output signal when the step change occurs by outputting at least one delayed demodulated sample to an output signal path upon occurrence of the step change, including switching the at least one delayed demodulated sample to the output signal path and thereafter switching the demodulated samples to the output signal path.
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 to output the demodulated signal via an output line;
- a cancellation circuit to cancel a portion of the demodulated signal caused by a change in the controlled oscillator frequency signal;
- and
- a switch coupled to the output line and to couple the cancellation circuit to the output line after the change in the controlled oscillator frequency, the switch otherwise controlled to allow the demodulated signal to be output via the output line.
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 apply a correction to subtract an undesired impulse within the demodulated signal caused by a change in the controlled oscillator frequency, the correction based on a timing and magnitude of the change in the controlled oscillator frequency.
Dependencies are inferred from the claim text.