Timing control circuit for guided wave radar level transmitter

A guided wave radar (GWR) level transmitter comprising:

• a timing circuit including a first oscillator circuit and a second oscillator circuit, wherein the first oscillator circuit is configured to produce a first signal having a first frequency to be transmitted along a waveguide probe toward a media surface, and wherein the second oscillator is configured to produce a second signal having a second frequency;
• a coincidence circuit configured to produce a coincidence signal indicative of phase shifts created by a difference between the first and second frequencies;
• and
• a microcontroller configured to:
• determine a stretching factor based on the coincidence signal and at least one of the first and second signals;
• calculate, in response to a determination that the stretching factor is within a first range, a distance between the media surface and a proximal end of the waveguide probe using the stretching factor;
• and
• adjust, in response to a determination that the stretching factor is outside of a second range, at least one of the first and second oscillator circuits to adjust the difference between the first and second frequencies.