Electrical Engineering - phase shifter circuit needed

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Author

phase shifter circuit needed

Patrick

2005-07-04, 4:25 am

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 a
180-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

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