Interface between radio receiver and baseband receiver and a method for converting RF-signals to BB-signals

1. A receiver system comprising an interface between a radio receiver on a radio frequency (RF)-side and a baseband receiver on a baseband (BB)-side, wherein the receiver comprises means for receiving radio frequency signals and an analogue-to-digital converter for converting received analogue signals to digital signals, wherein the digital signals are further processed in the baseband receiver by a digital signal processing unit, and wherein the analogue-to-digital converter is a sigma-delta converter comprising a sigma-delta modulator on the RF-side and a decimation filter on the BB-side, wherein the sigma-delta modulator and the decimation filter are connected only by single-bit in-phase (I) and quadrature (Q) streams output lines, where no additional control of the RF side is necessary and a splitting between the RF/BB interface gives full control of a decimation filter design.

2. The receiver system comprising an interface between a radio receiver on the RF-side and a baseband receiver on a BB-side according to claim 1 , wherein the decimation filter has a sampling rate and a FFT-length and the decimation filter is operable for selecting its sampling rate and its FFT-length according to a signal-to-noise ratio of the radio receiver.

3. The receiver system comprising an interface between a radio receiver on the RF-side and a baseband receiver on a BB-side according to claim 1 , wherein the sigma-delta modulator is a multi-bit analog sigma-delta modulator.

4. The receiver system comprising an interface between a radio receiver on the RF-side and a baseband receiver on a BB-side according to claim 1 , wherein the sigma-delta modulator comprises single-bit I and Q streams output lines connected to the baseband receiver.

5. The receiver system comprising an interface between a radio receiver on the RF-side and a baseband receiver on a BB-side according to claim 1 , wherein the decimation filter is operable for selecting various output sampling frequencies.

6. The receiver system comprising an interface between a radio receiver on the RF-side and a baseband receiver on a BB-side according to claim 1 , wherein the baseband receiver includes a signal-to-noise estimator.

7. The receiver system comprising an interface between a radio receiver on the RF-side and a baseband receiver on a BB-side according to claim 6 , wherein the signal-to-noise estimator is connected to switches for selectable switching between different decimation filters and an output switch for outputting the digital signal.

8. A method for converting an analog radio-frequency signal received by a radio receiver on a radio-frequency side to a digital baseband signal in a baseband receiver on a baseband side using a sigma-delta modulator on the radio frequency (RF) side and a decimation filter on the baseband (BB) side, wherein the sigma-delta modulator and the decimation filter are connected only by single-bit in-phase (I) and quadrature (Q) streams output lines, wherein a signal-to-noise ratio of the radio receiver is estimated and according to the signal-to-noise ratio a decimation filter on the baseband side is selected.

9. The method for converting a radio-frequency signal received by a radio receiver on a radio-frequency side to a baseband signal in a baseband receiver on a baseband side according to claim 8 , wherein a sampling rate and a FFT-length of the decimation filter is selected.

10. The method for converting a radio-frequency signal received by a radio receiver on a radio-frequency side to a baseband signal in a baseband receiver on a baseband side according to claim 8 , wherein at a low signal-to-noise ratio the sampling rate is decimate to a smallest sampling frequency of the decimation filter and do decimation before the FFT.

11. The method for converting a radio-frequency signal received by a radio receiver on a radio-frequency side to a baseband signal in a baseband receiver on a baseband side according to claim 8 , wherein at a high signal-to-noise ratio the sampling rate is decimate to a higher sampling frequency of the decimation filter and do part of a decimation inside the FFT.

12. The receiver system comprising an interface between a radio receiver on the RF-side and a baseband receiver on a BB-side according to claim 2 , wherein the sigma-delta modulator is a multi-bit analog sigma-delta modulator.

13. The receiver system comprising an interface between a radio receiver on the RF-side and a baseband receiver on a BB-side according to claim 12 , wherein the sigma-delta modulator comprises single-bit I and Q streams output lines connected to the baseband receiver.

14. The receiver system comprising an interface between a radio receiver on the RF-side and a baseband receiver on a BB-side according to claim 13 , wherein the decimation filter is operable for selecting various output sampling frequencies.

15. The receiver system comprising an interface between a radio receiver on the RF-side and a baseband receiver on a BB-side according to claim 14 , wherein the baseband receiver includes a signal-to-noise estimator.

16. The method for converting a radio-frequency signal received by a radio receiver on a radio-frequency side to a baseband signal in a baseband receiver on a baseband side according to claim 9 , wherein at a low signal-to-noise ratio the sampling rate is decimate to a smallest sampling frequency of the decimation filter and do decimation before the FFT.

17. The method for converting a radio-frequency signal received by a radio receiver on a radio-frequency side to a baseband signal in a baseband receiver on a baseband side according to claim 16 , wherein at a high signal-to-noise ratio the sampling rate is decimate to a higher sampling frequency of the decimation filter and do part of a decimation inside the FFT.