Multi-tuner variable low IF receiver for multi-channel applications
View Patent ↗Systems and methods for demodulating a plurality of contiguous channels contained within a bandlimited portion of a radio-frequency (RF) input signal are provided. In an embodiment, the bandlimited portion of the RF input signal is down-converted to baseband. After down-conversion, the bandlimited portion overlaps at baseband with a mirror image of the bandlimited portion. The plurality of contiguous channels within the down-converted signal similarly overlap at baseband and subsequently occupy a bandwidth substantially equal to half that required before down-converting. Image rejection is performed in the digital domain to recover each of the plurality of overlapping channels.
1. A variable low intermediate-frequency (IF) receiver, comprising:
a plurality of tuners, each tuner having an in-phase path and a quadrature path configured to down-convert a bandlimited portion of an RF input signal and a mirror image of the bandlimited portion of the RF input signal to baseband to provide as output a digital in-phase signal and a digital quadrature signal, respectively, wherein a group of contiguous channels are contained within the bandlimited portion of the RF input signal; and
an image canceller coupled to the digital in-phase and quadrature signals, the image canceller configured to perform image rejection on the digital in-phase and quadrature signals to recover a plurality of channels among the group of contiguous channels.
2. The variable low IF receiver of claim 1 , wherein the bandlimited portion is defined by the two outermost channels of the plurality of channels.
3. The variable low IF receiver of claim 2 , wherein the bandlimited portion is the narrowest bandlimited portion of the RF input signal containing the plurality of channels.
4. The variable low IF receiver of claim 1 , wherein the in-phase path comprises:
a mixer configured to multiply the RF input signal with a local oscillator signal having a frequency centered in the bandlimited portion of the RF input signal to provide as output a mixed in-phase signal.
5. The variable low IF receiver of claim 4 , wherein the in-phase path further comprises:
a low-pass filter having a bandwidth less than or substantially equal to one-half the bandwidth of the bandlimited portion of the RF input signal, the low-pass filter coupled to the mixed in-phase signal and configured to filter the mixed in-phase signal to provide as output a filtered in-phase signal.
6. The variable low IF receiver of claim 5 , wherein the bandwidth of the low-pass filter is configured to be dynamically adjusted based on the plurality of channels.
7. The variable low SF receiver of claim 6 , wherein the bandwidth of the low-pass filter is configured to be dynamically adjusted to reduce a power requirement of the low-pass filter.
8. The variable low IF receiver of claim 5 , wherein a gain of the mixer is configured to be dynamically adjusted based on the bandwidth of the low-pass filter.
9. The variable low IF receiver of claim 5 , wherein the in-phase path further comprises:
an analog-to-digital converter (ADC) coupled to the filtered in-phase signal, the ADC configured to digitize the filtered in-phase signal to provide as output the digital in-phase signal.
10. The variable low IF receiver of claim 9 , wherein a sampling frequency of the ADC is determined based on the bandwidth of the bandlimited portion of the RF input signal.
11. The variable low IF receiver of claim 10 , wherein the sampling frequency of the ADC is configured to be dynamically adjusted based on the plurality channels.
12. The variable low IF receiver of claim 11 , wherein the sampling frequency of the ADC is configured to be dynamically adjusted to reduce a power requirement of the ADC.
13. The variable low IF receiver of claim 1 , wherein the quadrature path comprises:
a mixer configured to multiply the RF input signal with a local oscillator signal having a frequency centered in the bandlimited portion of the RF input signal to provide as output a mixed quadrature signal.
14. The variable low IF receiver of claim 13 , wherein the quadrature path further comprises:
a low-pass filter having a bandwidth less than or substantially equal to one-half the bandwidth of the bandlimited portion of the RF input signal, the low-pass filter coupled to the mixed quadrature signal and configured to filter the mixed quadrature signal to provide as output a filtered quadrature signal.
15. The variable low IF receiver of claim 14 , wherein the bandwidth of the low-pass filter is configured to be dynamically adjusted based on the plurality of channels.
16. The variable low IF receiver of claim 15 , wherein the bandwidth of the low-pass filter is configured to be dynamically adjusted to reduce a power requirement of the low-pass filter.
17. The variable low IF receiver of claim 14 , wherein a gain of the mixer is configured to be dynamically adjusted based on the bandwidth of the low-pass filter.
18. The variable low IF receiver of claim 14 , wherein the quadrature path further comprises:
an analog-to-digital converter (ADC) coupled to the filtered quadrature signal, the ADC configured to digitize the filtered quadrature signal to provide as output the digital quadrature signal.
19. The variable low IF receiver of claim 18 , wherein a sampling frequency of the ADC is determined based on the bandwidth of the bandlimited portion of the RF input signal.
20. The variable low IF receiver of claim 19 , wherein the sampling frequency of the ADC is configured to be dynamically adjusted based on the plurality channels.
21. The variable low IF receiver of claim 20 , wherein the sampling frequency of the ADC is configured to be dynamically adjusted to reduce a power requirement of the ADC.
22. The variable low IF receiver of claim 1 , wherein each of the plurality of tuners down-converts a different bandlimited portion of the RF input signal.
23. The variable low IF receiver of claim 1 , wherein each channel among the group of contiguous channels is recovered.