Hi,


what do you mean by "the filter used in the mixer"? Are you deliberately adding a filter, or do you mean just some parasitic RC? Anyway a bandpass filter can be designed to have zero phase shift at the center frequency. Likewise if you mix the signal down to zero IF, the phase shift is zero at DC. I guess its possible (in theory anyway) to design the receiver with zero phase shift at one frequency. The wider your bandwidth, the less the phase variation over frequency.


regards,
Aaron

Hi,


it depends on the bandwidth of your low-pass filter. Definitely the phase shift is not going to be zero, but if the bandwidth is wide enough, then the phase shift will be minimal.

In your case, with a 50 MHz IF, your LPF is probably going to cause considerable phase shift. Off the top of my head you could:

1. Use a bandpass filter instead.

2. Digitize the signal first and use a digital filter. You will need a pretty high sampling rate so that your anti-aliasing filter doesn't cause any phase shift.

3. Choose a lower IF?

When you say you need the exact phase, I assume you mean w.r.t the transmitted signal right? If you describe your application a bit you will probably get better responses.


regards,
Aaron