EMI consideration for Microwave Sensor Module
I guess 1.5cm is just a guideline so that customers do not come back to ask why it isn't working as expected. But 15cm for such sensors are really long. Ideally, we should have an amplifier as close to the IF as possible so that the desired IF signal is always larger than any impinging interferer. If you have a shielded coax, it would definitely work better.