Combined Low-IF/direct down conversion baseband architecture for 3G GSM/WCDMA receivers

1. A radio receiver for receiving signals of at least two different communication standards, including a narrow band signal having a narrow bandwidth and a wide band signal having a wide bandwidth, comprising:

a shared radio frequency (RF) front-end, said shared RF front-end receiving said wide band signal during at least one period of operation and downconverting, in a single downconversion, said wide band signal directly to baseband, said shared RF front-end receiving said narrow band signal during at least another period of operation and downconverting, in a single downconversion, said narrow band signal to a low intermediate frequency (Low-IF) no more than a few times the bandwidth of the narrow band signal;

a baseband processing chain coupled to said shared RF front-end and operating on said downconverted wide band signal to extract desired data from said downconverted wide band signal; and

a Low-IF processing chain, separate from the baseband processing chain, coupled to said shared RF front-end in parallel to said baseband processing chain and operating on said downconverted narrow band signal to extract desired data from said downconverted narrow band signal.

2. The apparatus of claim 1 wherein said wide band signal is a wide band code division multiple access (WCDMA) type signal.

3. The apparatus of claim 1 wherein said narrow band signal is a Global System for Mobile Communications (GSM) type signal.

4. The apparatus of claim 1 wherein said downconverted wide band signal is a quadrature signal having an I channel and a Q channel.

5. The apparatus of claim 1 wherein said downconverted narrow band signal is a quadrature signal having an I channel and a Q channel.

6. The apparatus of claim 1 wherein said baseband processing chain and said Low-IF processing chain are formed on a single integrated circuit.

7. The apparatus of claim 6 wherein said shared RF front-end is formed on a different integrated circuit.

8. The apparatus of claim 1 wherein said shared RE front-end, baseband processing chain and Low-IF processing chain are formed on a single integrated circuit.

9. The apparatus of claim 1 wherein said shared RF front-end, baseband processing chain and Low-IF processing chain are formed using CMOS technology.

10. The apparatus of claim 1 wherein said shared RF front-end, baseband processing chain and Low-IF processing chain are formed using BiCMOS technology.

11. The apparatus of claim 1 wherein said shared RF front-end, baseband processing chain and Low-IF processing chain are formed using Silicon Germanium (SiGe) technology.

12. The apparatus of claim 1 wherein said shared RF front-end, baseband processing chain and Low-IF processing chain are formed using Gallium Arsenide (GaAs) technology.

13. The apparatus of claim 1 wherein said shared RF front-end further comprises: a plurality of low noise amplifiers (LNA) in parallel connection with one another; a mixer connected in series with said plurality of LNAs; a voltage controlled oscillator (VCO) providing a oscillating reference signal to said mixer; and a pre-filter block connected in series with said mixer, said pre-filter block performing amplification and filtering functions.

14. The apparatus of claim 13 wherein each of said plurality of LNAs is capable of amplifying a different frequency range of RF signals.

15. The apparatus of claim 1 , said baseband processing chain further comprising: a baseband blocker filter; a DC offset control circuit connected in series with said baseband blocker filter; and an analog to digital converter connected in series with said DC offset control circuit.

16. A radio receiver for receiving signals of at least two different communication standards, including a narrow band signal having a narrow bandwidth and a wide band signal having a wide bandwidth, comprising:

a shared radio frequency (RE) front-end, said shared RF front-end receiving said wide band signal during at least one period of operation and downconverting, in a single downconversion, said wide band signal directly to baseband, said shared RE front-end receiving said narrow band signal during at least another period of operation and downconverting, in a single downconversion, said narrow band signal to a low intermediate frequency (Low-IF) no more than a few times the bandwidth of the narrow band signal:

a baseband processing chain coupled to said shared RE front-end and operating on said downconverted wide band signal to extract desired data from said downconverted wide band signal, said baseband processing chain comprising: a first and a second baseband blocker filter; a first and a second DC offset control circuit connected in series with said first and second baseband blocker filters, respectively; and a first and a second analog to digital converter connected in series with said first and second DC offset control circuits, respectively, wherein said first baseband blocker filter, first DC offset control circuit, and first analog to digital converter form an I channel path of said baseband processing chain, and wherein said second baseband blocker filter, second DC offset control circuit, and second analog to digital converter form a Q channel path of said baseband processing chain; and

a Low-IF processing chain coupled to said shared RF front-end and operating on said downconverted narrow band signal to extract desired data from said downconverted narrow band signal.

17. The apparatus of claim 1 , said Low-IF processing chain further comprising: a Low-IF blocker filter; an automatic gain control (AGC) filter connected in series with said Low-IF blocker filter; a DC offset control circuit connected in series with said AGC filter; and a demodulator connected in series with said DC offset control circuit.

18. A radio receiver for receiving signals of at least two different communication standards, including a narrow band signal having a narrow bandwidth and a wide band signal having a wide bandwidth, comprising:

a shared radio frequency (RF) front-end, said shared RF front-end receiving said wide band signal during at least one period of operation and downconverting, in a single downconversion, said wide band signal directly to baseband, said shared RF front-end receiving said narrow band signal during at least another period of operation and downconverting, in a single downconversion, said narrow band signal to a low intermediate frequency (Low-IF) no more than a few times the bandwidth of the narrow band signal;

a baseband processing chain coupled to said shared RF front-end and operating on said downconverted wide band signal to extract desired data from said downconverted wide band signal; and

a Low-IF processing chain coupled to said shared RE front-end and operating on said downconverted narrow band signal, operable to extract desired data from said downconverted narrow band signal, said Low-IF processing chain comprising: a first and a second Low-IF blocker filter; a first and a second automatic gain control (AGC) filter connected in series with said first and second Low-IF blocker filters, respectively; a first and a second DC offset control circuit connected in series with said first and second AGC filters, respectively; and a first and a second demodulator connected in series with said first and second DC offset control circuits, respectively, wherein said first Low-IF blocker filter, first AGC filter, first DC offset control circuit, and first demodulator form an I channel path of said Low-IF processing chain, and wherein said second Low-IF blocker filter, second AGC filter, second DC offset control circuit, and second demodulator form a Q channel path of said Low-IF processing chain.

19. A method for receiving signals of at least two different communication standards, including a narrow band signal having a narrow bandwidth and a wide band signal having a wide bandwidth, comprising:

receiving said wide band signal during at least one period of operation at a shared radio frequency (RF) front-end;

downconverting at said shared RF front-end, in a single downconversion, said wide band signal directly to baseband;

receiving said narrow band signal during at least another period of operation at said shared RF front-end receiving;

downconverting at said shared RF front-end, in a single downconversion, said narrow band signal to a low intermediate frequency (Low-IF) no more than a few times the bandwidth of the narrow band signal;

at a baseband processing chain coupled to said shared RF front-end, operating on said downconverted wide band signal to extract desired data from said downconverted wide band signal; and

at a Low-IF processing chain separate from said baseband processing chain and coupled to said shared RE front-end in parallel with said baseband processing chain, operating on said downconverted narrow band signal to extract desired data from said downconverted narrow band signal.

20. A system for receiving signals of at least two different communication standards, including a narrow band signal having a narrow bandwidth and a wide band signal having a wide bandwidth, comprising:

means for receiving said wide band signal during at least one period of operation at a shared radio frequency (RF) front-end; means for downconverting at said shared RF front-end, in a single downconversion, said wide band signal directly to baseband; means for receiving said narrow band signal during at least another period of operation at said shared RF front-end receiving; means for downconverting at said shared RF front-end, in a single downconversion, said narrow band signal to a low intermediate frequency (Low-IF) no more than a few times the bandwidth of the narrow band signal;

means for a baseband processing chain coupled to said shared RF front-end, operating on said downconverted, wide band signal to extract desired data from said downconverted wide band signal; and

means for a Low-IF processing chain, separate from said means for baseband processing, coupled to said shared RF frontend in parallel with said baseband processing chain, operating on said downconverted narrow band signal to extract desired data from said downconverted narrow band signal.