A good impedance matching network should match a load to within a maximum SWR (typically less than 2?).
But with a varying load (i.e. Antenna in varying surroundings), are there any techniques that match a widely varying load to a less widely varying match?
In other words, if the plotted range of a given antenn's loads on a Smith chart were the size, so to speak, of an SWR circle of 3.5, is there a matching technique that results in a matched impedance that is always less than 2?
UPDATE
In my particular case, I'm working with a Maxim 7044 transmitter at 320MHz in a wireless sensor. So large SWR voltages aren't the problem. I want to maintain an SWR < 2 under all conditions, with an antenna that occupies most of a quadrant of the Smith chart.
Best Answer
You can use a stripline return loss DC20 directional coupler to tap -20dB of the reflected power into an RSSI chip or a Schottky diode amp and measure the reflected energy due to antenna loading effects on standing waves.
In the old days I did this to tune a small dipole in VHF band and discovered this method is a great motion sensor for over 10 wave lengths (size of lab)
What you do with the variable phase and amplitude feedback is up to you. It would be theoretically possible to inject the conjugate feedback signal to modulate the Tx, but I doubt it is worth it.