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

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.