[Antennas] Return Loss Bridge Construction
Ronald KA4INM Youvan
[email protected]
2002年5月27日 01:38:38 -0400
> However, it is a precision instrument,
> is expensive because of the precise isolation requirements between the
> ports, and it requires a couple of expensive pieces of test equipment to
> use with it, namely a spectrum analyzer and tracking signal generator.
However, a return loss bridge can be built inexpensively if done with
some care and used with an RF sweep generator, a diode detector, and
a simple oscilloscope, the only caveat is: If the sweep generator
doesn't put out around +20 dBm and you don't use a hot carrier diode
detector, the trace will be too small to be useable. (I suppose you
could follow a lower powered generator with a MMIC amplifier or two.)
When you put an antenna on the DUT port (positioned in the free)
the frequencies where energy is lost TO RADIATION are what show on the scope.
(as a negative bell curve) Great for measuring the bandwidth!
The transmission line in use (match or length) changes this very little
(only as an antenna tuner would) although the match can be measured.
You can use a good directional coupler to observe the same things.
It is the ideal device for antenna tuning and development on a budget.
73 (= Best Regards) de: Ron [email protected]
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