Method and system for impairment shifting
A method and system for impairment shifting is disclosed and may include receiving one or more radio frequency (RF) analog television signals in a receiver of a communication device, downconverting the received one or more received RF analog television signals to baseband frequencies, synchronizing the receiver to the one or more received RF analog television signals, and adjusting a frequency of one or more local oscillators in the receiver to configure in-phase/quadrature (I/Q) mismatch of a picture carrier signal to fall near a sound carrier signal in the received RF analog television signals. The frequency of the one or more local oscillators may be adjusted to configure a DC offset impairment to fall between luminance and chrominance harmonics at baseband in the analog television signals. I/Q imbalanced impairments may be configured with about 300 kHz separation from the sound carrier signal.
1. A method for communication, the method comprising:
in a communication device comprising first and second downconverters and a processor:
receiving, by the first down-converter, a radio frequency (RF) signal comprising a first desired signal and a second desired signal;
downconverting, by the first down-converter, the RF signal to a first baseband signal using a first oscillating signal;
receiving the RF signal using the second down-converter;
downconverting, by the second down-converter, the RF signal to a second baseband signal using a second oscillating signal;
receiving the first and second baseband signals in the baseband processor; and
independently controlling, using the processor, the first oscillating signal and the second oscillating signal to generate a DC offset impairment signal located between the first desired signal and the second desired signal at baseband.
2. The method according to claim 1 , comprising processing in-phase and quadrature (I/Q) signals in said communication device.
3. The method according to claim 2 , comprising controlling the first and second oscillating signals to configure I/Q imbalanced impairments caused by residual in-phase and quadrature mismatch of desired signals to fall between the desired signals at baseband.
4. The method according to claim 1 , wherein the RF signal comprises a satellite television signal.
5. The method according to claim 1 , wherein the RF signal comprises a cable television signal.
6. The method according to claim 1 , wherein the communication device is a direct conversion receiver.
7. The method according to claim 1 , comprising detecting, using a carrier detect module, a frequency of the impairment signal from assessment of the frequency spectrum of baseband signals generated by the down-conversion by the first and second down-converters.
8. The method according to claim 7 , comprising calculating frequency adjustments for the first and second oscillating signals based on the detected frequency of the impairment signal.
9. The method according to claim 8 , comprising controlling the first and second oscillating signals based on the calculated frequency adjustments.
10. The method according to claim 1 , comprising adjusting oscillators that generate the first and second oscillating signals, the adjusting based on a control signal from a phase-locked loop.
11. A system for communication, the system comprising:
a first downconverter operable to receive a radio frequency (RF) signal comprising a first desired signal and a second desired signal, wherein the first downconverter is operable to convert the RF signal to a first baseband signal using a first oscillating signal;
a second downconverter operable to receive the RF signal, wherein the second downconverter is operable to convert the RF signal to a second baseband signal using a second oscillating signal; and
a processor operable to receive the first baseband signal and the second baseband signal, wherein the processor is operable to independently control the first oscillating signal and the second oscillating signal to generate a DC offset impairment signal located between the first desired signal and the second desired signal at baseband.
12. The system according to claim 11 , wherein the first and second downconverter are operable to process in-phase and quadrature (I/Q) signals.
13. The system according to claim 12 , wherein the processor I operable to control the first and second oscillating signals to configure I/Q imbalanced impairments caused by residual in-phase and quadrature mismatch of desired signals to fall between the desired signals at baseband.
14. The system according to claim 11 , wherein the RF signal comprises a satellite television signal.
15. The system according to claim 11 , wherein the RF signal comprises a cable television signal.
16. The system according to claim 11 , wherein the first and second down-converters and processor are in a direct conversion receiver.
17. The system according to claim 11 , comprising a carrier detect module that is operable to detect a frequency of the impairment signal from assessment of the frequency spectrum of baseband signals generated by the down-conversion by the first and second down-converters.
18. The system according to claim 17 , comprising a local oscillator control module that is operable to calculate frequency adjustments for the first and second oscillating signals based on the detected frequency of the impairment signal.
19. The system according to claim 18 , comprising a frequency control module that is operable to control the first and second oscillating signals based on the calculated frequency adjustments.
20. The system according to claim 19 , wherein the frequency control module is operable to adjust oscillators that generate the first and second oscillating signals, the adjusting based on a control signal from a phase-locked loop.