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Application:
Four (4) Port Directional couples are
typically used to accurately and conveniently measure incident and reflected
power so as to determine;
VSWR
LOSS POWER SPLITTING & COMBINING
SIGNAL
SAMPLING SIGNAL INJECTION POWER FLOW
MONITORING
These are all very important parameters,
particularly in the Telecommunications market today. 3dB Hybrid couplers are
now frequently used for combining applications for in-building distribution.
Characteristics:
The output signals are unequal in
amplitude. The larger signal is at the main-line output port. The smaller
signal is in the coupled port (except for the 3 dB coupler).
The Main line insertion loss depends
upon the coupled port, coupling value.
There is high isolation between the
coupled port and the output of the main line.
The Key characteristics of a directional
coupler include coupling coefficient, coupling flatness, main-line loss and
directivity.
Explanation of Terms:
Coupling Coefficient
Coupling Flatness
Main-line Insertion Loss
Directivity
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The nominal coupling is the ratio in dB of the coupled port power relative to the input power level.
The peak to peak variation of coupling in dB.
The average
value over the frequency range.
The net
unrecoverable power loss in dB based on one way transmission through the
coupler.
The
ratio in dB of power at the coupled port when fed in the forward direction to
the power at the coupled port when fed in the reverse direction at the same
power level.
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