Unfortunately FMCW lidar is sweeping the lasers across the same band. You don’t need the exact frequency just a beat frequency that’s within your detection Bw.
Also balanced detectors have something called common mode rejection. This is not infinite. In high volume applications it’s difficult for this to be >25dB but you can buy some devices >35dB.
Given that Lidar dynamic range is ~100dB you will definitely see the DC. I’ve not thought about this too much but it seems like an issue for the AGC as your demodulator won’t be bothered by it.
Also balanced detectors have something called common mode rejection. This is not infinite. In high volume applications it’s difficult for this to be >25dB but you can buy some devices >35dB.
Given that Lidar dynamic range is ~100dB you will definitely see the DC. I’ve not thought about this too much but it seems like an issue for the AGC as your demodulator won’t be bothered by it.