Quadrature receiver sampling architecture
View Patent ↗Quadrature receiver sampling architecture. A signal ADC performs analog to digital conversion for both I and Q streams. An analog MUX selects the appropriate I and the Q baseband analog input streams for input to the ADC at the appropriate time. A digital filter may also be employed to compensate for any introduced delay between the samples of the I and Q channel when seeking to recover the symbols that have been transmitted to a communication receiver that employs this quadrature receiver architecture and/or signal processing. In one embodiment, if an ADC is clocked at a rate of substantially twice the sample rate of the I and Q channels, there will be a one-half sample clock delay between the digital I and digital Q data at the output of the ADC. This delay is then removed before the demodulator processes the input signals to recover the transmitted symbols.
1. A communication receiver, comprising:
an analog front-end that is operable to receive an analog I stream and an analog Q stream;
a digital processing unit that is communicatively coupled to the analog front-end;
wherein the analog front-end includes a multiplexor and a single analog to digital convener that operate cooperatively to perform alternative digital sampling of the analog I stream and the analog Q stream thereby convening the analog I stream and the analog Q stream into a digital I stream and a digital Q stream; and
the digital processing unit is operable to perform decimation and de-rotation of a digital sample of the digital I stream and the digital Q stream, the rotation being introduced during the analog to digital conversion of the analog I stream and the analog Q stream, the digital processing unit includes a digital signal processor, wherein the digital signal processor performs mathematical operations on the digital I stream and the digital Q stream to compensate for delay that occurs during the analog to digital conversion of the analog I stream and the analog Q stream thereby performing the de-rotation of the digital sample of the digital I stream and the digital Q stream.
2. The communication receiver of claim 1 , further comprising a radio frequency interface that is operable to extract the analog I stream and the analog Q stream from a received analog signal.
3. The communication receiver of claim 1 , wherein a selector of the multiplexor and the single analog to digital convener being clocked at a frequency that is substantially twice a digital sampling frequency of the analog I stream and the analog Q stream.
4. The communication receiver of claim 1 , wherein a selector of the multiplexor being clocked a first frequency that is substantially twice a digital sampling frequency of the analog I stream and the analog Q stream; and
the single analog to digital convener being clocked at a second frequency that is substantially twice the digital sampling frequency of the analog I stream and the analog Q stream.
5. The communication receiver of claim 1 , wherein the analog front-end further comprises a sample and hold element that is communicatively coupled to the multiplexor.
6. The communication receiver of claim 5 , wherein the analog I stream and the analog Q stream are provided to the multiplexor;
an output of the multiplexor is provided to the sample and hold element; and
an output of the sample and hold element is provided to the single analog to digital converter.
7. The communication receiver of claim 5 , wherein the analog front-end further comprises at least one additional sample and hold element; and
wherein the analog I stream is provided to the sample and hold element;
the analog Q stream is provided to the at least one additional sample and hold element;
outputs from the sample and hold element and the at least one additional sample and hold element are provided to the multiplexor; and
an output of the multiplexor is provided to the single analog to digital converter.
8. The communication receiver of claim 1 , wherein the communication receiver comprises at least one of a base station receiver, a mobile receiver, a set top box, a tower receiver, a mobile unit, and an high definition television (HDTV) set top box receiver.
9. The communication receiver of claim 8 , wherein at least one of the base station receiver and the tower receiver comprises a wireless tower.
10. The communication receiver of claim 8 , wherein at least one of the set top box and the HDTV set top box receiver comprises a local satellite dish.
11. The communication receiver of claim 1 , wherein the communication receiver is contained within a transceiver, the transceiver also comprises a communication transmitter.
12. The communication receiver of claim 2 , wherein the analog signal is received via a wireless communication channel.
13. A satellite communication system, comprising:
a local satellite dish that is operable to receive an analog signal transmitted from a satellite via a wireless communication channel; and
a set top box, communicatively coupled to the local satellite dish via a coaxial cable, that receives the analog signal received by the local satellite dish;
wherein the set top box includes an analog front-end and a digital processing unit, the analog front-end includes a radio frequency interface;
the analog front-end is operable to receive the analog signal transmitted from the satellite and to extract an analog I stream and an analog Q stream therefrom;
the digital processing unit is communicatively coupled to the analog front-end;
the analog front-end includes a multiplexor and a single analog to digital converter that operate cooperatively to perform alternative digital sampling of the analog I stream and the analog Q stream thereby converting the analog I stream and the analog Q stream into a digital I stream and a digital Q stream; and
the digital processing unit is operable to perform decimation and de-rotation of a digital sample of the digital I stream and the digital Q stream, the rotation being introduced during the analog to digital conversion of the analog I stream and the analog Q stream; wherein the digital processing unit includes:
a digital signal processor, a delay element, and a half band interpolating filter;
the delay provided by the delay element is substantially comparable to a time comprises a duration that is substantially comparable to a time required to perform a half band interpolating filtering; and
wherein the delay element and the half band interpolating filter operate cooperatively to compensate for delay that occurs during the analog to digital conversion of the analog I stream and the analog Q stream thereby performing the de-rotation of the digital sample of the digital I stream and the digital Q stream.
14. The satellite communication system of claim 13 , wherein the analog front-end further comprises a radio frequency interface that is operable to extract the analog I stream and the analog Q stream from the received analog signal.
15. The satellite communication system of claim 13 , wherein the analog front-end further comprises a sample and hold element that is communicatively coupled to the multiplexor.
16. A communication receiver, comprising:
an analog front-end that is operable to receive an analog I stream and an analog Q stream;
a digital processing unit that is communicatively coupled to the analog front-end;
wherein the analog front-end includes a multiplexor and a single analog to digital convener that operate cooperatively to perform alternative digital sampling of the analog I stream and the analog Q stream thereby convening the analog I stream and the analog Q stream into a digital I stream and a digital Q stream; and
the digital processing unit is operable to perform decimation and de-rotation of a digital sample of the digital I stream and the digital Q stream, the rotation being introduced during the analog to digital conversion of the analog I stream and the analog Q stream, wherein the digital processing unit includes:
a digital signal processor, a delay element, and the half band interpolating filter;
the delay provided by the delay element is substantially comparable to a time includes a duration that is substantially comparable to a time required to perform the half band interpolating filtering; and
wherein the delay element and the half band interpolating filter operate cooperatively to compensate for any delay that occurs during the analog to digital conversion of the analog I stream and the analog Q stream thereby performing the de-rotation of the digital sample of the digital I stream and the digital Q stream.
17. The communication receiver of claim 16 , further comprising a radio frequency interface that is operable to extract the analog I stream and the analog Q stream from a received analog signal.
18. The communication receiver of claim 16 , wherein a selector of the multiplexor and the single analog to digital convener being clocked at a frequency that is substantially twice a digital sampling frequency of the analog I stream and the analog Q stream.
19. The communication receiver of claim 16 , wherein a selector of the multiplexor being clocked a first frequency that is substantially twice a digital sampling frequency of the analog I stream and the analog Q stream; and
the single analog to digital convener being clocked at a second frequency that is substantially twice the digital sampling frequency of the analog I stream and the analog Q stream.
20. The communication receiver of claim 16 , wherein the analog front-end further comprises a sample and hold element that is communicatively coupled to the multiplexor.
21. The communication receiver of claim 20 , wherein the analog I stream and the analog Q stream are provided to the multiplexor;
an output of the multiplexor is provided to the sample and hold element; and
an output of the sample and hold element is provided to the single analog to digital converter.
22. The communication receiver of claim 20 , wherein the analog front-end further comprises at least one additional sample and hold element; and
wherein the analog I stream is provided to the sample and hold element;
the analog Q stream is provided to the at least one additional sample and hold element;
outputs from the sample and hold element and the at least one additional sample and hold element are provided to the multiplexor; and
an output of the multiplexor is provided to the single analog to digital converter.
23. The communication receiver of claim 16 , wherein the communication receiver comprises at least one of a base station receiver, a mobile receiver, a set top box, a tower receiver, a mobile unit, and an high definition television (HDTV) set top box receiver.
24. The communication receiver of claim 23 , wherein at least one of the base station receiver and the tower receiver comprises a wireless tower.
25. The communication receiver of claim 23 , wherein at least one of the set top box and the HDTV set top box receiver comprises a local satellite dish.
26. The communication receiver of claim 16 , wherein the communication receiver is contained within a transceiver, the transceiver also comprises a communication transmitter.
27. The communication receiver of claim 17 , wherein the analog signal is received via a wireless communication channel.