On Nov 2, 11:22*pm, ashwanthh
wrote:
Hi all,

For my project, I want to perform Distance to fault measurement in the
cable connecting the antenna. The principle is that a signal should be
sent to the cable and using the forward and reflected voltage VSWR
should be calculated and should be viewed in a spectrum analyzer. My
question is

1. *What transducer is used to detect the transmitted/reflected signals
from the cable?

2. Should the transducer be connected in series or parallel?

Anyone, Please help

--
ashwanthh

Forward and reverse power are normally resolved using a "directional
coupler." Such a coupler can also be thought of as a bridge circuit.
Directional couplers can be built in various ways. For example, the
free-ware RFSim99 program, under tools--component--coupler shows
five different ways to build a directional coupler. That program
doesn't show the Wheatstone bridge form of directional coupler, but
those are also common, especially where a wide range of frequencies is
to be covered. Wheatstone bridges are generally used with equal (e.g.
50 ohm) arms in test and measurement equipment that runs low RF power
(because such a bridge must dissipate most of the RF power fed to it),
and with very unequal arms when high power is to be handled (resulting
in a low coupling factor; -40dB is common). Please note that
directional couplers must be designed for the impedance line they are
used with (and ideally, the calibration should be verified).

In your project to locate faults, you may wish to consider not only
the ratio of forward and reverse power (e.g., SWR), but also the phase
relationship between the two. The rate of change of phase as
frequency is changed should tell you how far away a single fault is;
multiple faults are more complicated.

Cheers,
Tom