Directional couplers are intended to measure the signals (produced by the forward and reverse waves) in between an amplifier and load. Yet there are also several other directional coupler applications. We will consider these here.
Phase Measuring Between Forward and Reverse Waves
It is one thing to measure signals that exist between the reverse and forward waves. Yet the directional couplers can also quantify the phase between them. Why would this information be useful to have? You are able to calculate the load’s complex impedance utilizing this data. A real world example of this practicality can be found with VNA’s Vectoriell Network Analyzers.
This matters as it is critical to hold the reflections as low as can be when the amplifier’s power transfers over to the load. The quantified signals from the directional coupler can be utilized to control a match box. This changes the unpredictable and potentially dangerous impedance from the load to a precise 50 Ω as measured by the amplifier.
Using the Forward Wave Signals for Regulation Systems
Yet another helpful application from direction couplers pertains to utilizing signals from the forward wave as a system of regulation. This allows you to ensure that the forward power remains constant. It means that the conditions can be kept consistent for thermal, physical, or chemical processes of the load itself. You might also regulate the load’s voltage directly.
Employing the Signals for Safeguarding the Entire System
The advantage with the reverse wave’s signal is that this can be employed to safeguard the entire system. Should the amplitude reach critical values that are too high then the forward power may be auto shut down or down-regulated. Real examples of this are after there is an arc in the coupler line or when an antenna gets flushed.
There would also be a harmonics of the reverse wave change in the event of a load mismatch of significance. This is why a higher level of harmonics could be utilized for the input of any protection system. It would be quantified on the reverse coupling port of the directional coupler via a high pass filter.