DC offset cancellation in WLAN

In direct convertion (Zero-IF) RX system RX DC offset must removed. In such an WLAN receiver high pass filter with low cornner frequendcy is often used to remove the DC offset. There are two ways to realize the high pass filter. (1) using AC couple directly to remove the DC offset. (2) using a negitive feedback with low pass filter to extract the DC offset and remove it. In WLAN receiver I only find (2) is used in some papers. Why no (1) is used in WLAN receiver?

IF you are ac coupled, what happens to the dc level after the capacitor if you receive the following sequence:

"1111111111111111111111111111111111111111111111111 11111111111111111111111111111111111111111111111111 1111111111111111111111111110" ?

Infact this will not happen...

I mean, there is OFDM modulation in between.
It has been proven that, cutting few kHz around DC in the overall WIFI signal spectrum there is only a negligible degradation in SNR.

The main reason of DC cancellation respect to high pass filtering is that the latter choice will need the use of non-integrated RC filters.

I hope it can help.

Mazz