I am building a two-way communication setup based on software defined radios.
Setup: The Tx needs to send a sinusoid to the Rx, and the Rx – after some processing – sends its own sinusoid in return. It is basically a ranging problem.
Problem: What I want is to keep the Tx LO running during this time (without any transmission) so that its phase can be compared with the phase of the incoming signal from the Rx later.
Equipment: Currently I am using HackRF SDRs but I can get USPRs if needed. If a specific hardware is required for this purpose, I would be glad to hear about that as well.
EDIT: I just thought of a simple way to pose the question again. Does a typical LO (in HackRF for example but in other devices as well) maintain phase continuity when switching from Tx to Rx mode?