Procedure and arrangement for DC offset compensation in a direct conversion receiver

摘要

The circuit comprises a mixer (1) and pass-band filter (3) prior to direct and indirect circuit branches leading to a summator providing an output signal in which compensation has been provided for the variable shift occurring within the direct conversion receiver. The circuit comprises a mixer (1) receiving an input signal (RF(t)) from an aerial, having been processed by a pass-band filter and or a low noise HF amplifier. Another mixer inputs receives a square signal input (LO(t)) from a local oscillator (2). The signal from the mixer output (Vout(t)) is passed through a pass-band filter (3), a programmable gain amplifier (4) and a low-pass filter (5). The output from this filter is applied to an analogue-digital converter linked to a memory (7). The memory output is applied to a summator (8) whose output (9) forms the output of the circuit. This forms the direct path. There is also an indirect path provided by a further loop (11-17). This provides a variable compensation for interference.