Harris DiamondCD Series, Техническое руководство

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4-34 888-2463-001 3/6/08
WARNING: Disconnect primary power prior to servicing.
Diamond Series™
Section 4 Theory of Operation
The rules for the operation of 3 dB quadrature hybrids are listed below. Rules number 4
and beyond may be derived from the first three. Other types of hybrids follow similar
sets of rules.
4.9.4.1 Splitting
a. A signal incident upon any one of the four symmetrical ports will split equally
between the opposite and cross ports.
b.
In a 3 dB hybrid, each output terminated in Z
o
(normally 50 Ohms) will receive
an amount of power 3 dB below the power into the input port. If both outputs are
terminated in 50 Ohms, half of the input power will be passed to each output port.
In this case, the voltage amplitude at each output port will be 0.707 times that at
the input port.
c. The signal at the opposite port will be in phase with the input, while the signal at
the cross (diagonal) port will be in quadrature (phase shifted by -90
o
).
d. Any mismatch at an output port will result in power reflected back into the
hybrid. Signals reflected back into the hybrid by a mismatch are treated in the
same manner as input signals incident upon that port.
4.9.4.2 Combining
a.
Two equal-amplitude signals applied in quadrature to adjacent ports will sum and
reappear at one opposite port.
b.
The sum port will be the port directly opposite the input port with lagging relative
phase, and diagonally across from the input port with leading phase.
c.
Any amplitude difference, or any phase difference other than 90
o
between the two
input signals, will result in power appearing at the fourth, or “reject,” port.
4.9.4.3 Hybrids In Attenuators
A special case occurs if a signal is input to port 1, and the two output ports see
mismatches whose impedances are identical in magnitude and phase. By rule 1, the
power is split and appears in quadrature at ports 2 and 3. Since the impedances at ports
2 and 3 are identical, the signals reflected back into ports 2 and 3 have the same
amplitude and are still in quadrature. By rule 5, the reflected signals add together, with
the sum appearing at port 4, the reject port. This is the basis for attenuator and phase-
shifter operation.