how to decide the corner frequency?

I am designing a ZIF receiver based on DVB-S and plan to use a loop to handle the dc offset problem. the loop can be considered a high-pass filter, but how to decide the BW of the high-pass circuit?

Take a look at the DVB-S Specification. If it's OFDM, then see if any carriers are suppressed in the center of the signal. From that information, you can determine how wide the "dead spot" in the middle is, and determing your DC Offset compensation from that.

Dave
www.keystoneradio.com

It is certainly not OFDM, rather QPSK or higher order phase modulations I would say. Using a slicer is ok if it's bandwidth is substantially lower than the lowest modulation bandwidth so that's a first criterion. Another issue is if it's bursted communication or not. That can complicate things.