I'm looking to build to a phase shifter circuit that can supply about 60 degrees of phase shift at 70 MHz (bandwidth not important). The phase shift needs to be adjustable in real time, ie, with a variable R or C.
The catch is that the input and output of the network needs to remain matched to 50 ohms.
Can this even be done with purely passive components?
(Specifically, what I have is a transmission line that needs to provide a180-degree shift from the start of the line to the end. The problem is we have no way to precisely measure the length of the TL. So we need a way to adjust the "length" of the line in real time. Now, I'm aware of the trombone method, wherein a piece of TL is slid in and out to provide a variable lenght. However, this is a mechanical solution and not suited for the application; ergo I need a way simulate this behaviour)
Thanks very kindly