A Direct Conversion Receiver with Fast-Settling DC Offset Canceller

In direct conversion receivers, which down-convert RF signal to baseband directly, DC offset in the baseband signal significantly degrades receiver performance and thus the DC offset cancellation is one of the most important issues regarding the achievement of high receiving performance. This paper proposes a fast-settling DC offset canceller that eliminates DC offset using stored DC data estimated in advance so as to cancel residual DC offset by a feedback loop. Experimental results and computer simulation results show that the DC offset canceller can eliminate a DC offset within 5 [musec], although it does not remove the desired signal component so as not to degrade BER (bit error rate) performance, because cut-off frequency in the HPF (high-pass filter) characteristic due to DC offset cancellation can remain low.