Common Measurement Methods; Quick Adjustment Of Duplexer - Deepace KC901V Manual

Chapter Four Common Measurement Methods

4.1 Quick Adjustment of Duplexer

Duplexer is an important part of a repeater. Its insertion loss and isolation ratio
are related to the performance of the repeater. In frequency band which is used
commonly, KC901V can provide an operation range which is better than 95dB. User
can adjust the duplexer into the best state under its monitoring.
Prepared accessories: a 50Ωdummy load, 2 RF cables, necessary RF adaptors.
Fixing KC901V on the workbench is suggested.
tools: a socket spanner with a center hole, screwdrivers. If it's possible, fix the
duplexer which is under the test on the workbench.
Special settings: In the beginning of the adjustment, user can use middle speed
or high speed (FUNC, Speed). When doing the fine-tuning to the trap frequency point,
user should use Low speed, also insertion loss mode can be used as well.
Take band trap theory's six-cavity duplexer as an example to introduce the ad-
justing steps.
Set KC901V to S21 and then set its center and span to make the frequency range
cover the original frequency and the new frequency of the duplexer. AMP can be set
as 0dB or +10dB (AMP and ordinate range can be switched according to curve's posi-
tion.). After turn on system calibration, move mark1 and mark2 nearby duplexer's
new receiver frequency and transmitter frequency.
Firstly, use the instrument to measure the insertion loss of the RF cable (S21)
and shake the cable and adaptor at the same time to check if the curve shakes as well
to make sure if there is any bad contact. Cable's insertion loss should be as less as it
can be and be steady as well. Cable's quality should be good too so that it can provide
the good shielding layer. User can hang the cable in the air to check the position of
instrument's noise floor. In 450MHz, it's better below -100dB but at least up to -90dB.
Clean up the socket of the duplexer, and then connect one of the instrument's
RF port to duplexer's TX input port (usually noted as high). After that, connect in-
strument's another port to duplexer's ANT (antenna) port. Finally, connect the load to
the rest RX port (usually noted as low).(Chart 4-1).
Adjust three of the screws which near TX port to make the dip move to the posi-
tion which mark1 points at as well as to make them superposition possibly. Fine-tune
the screws step by step under the monitoring of mark1's S reading to make the min-
imum reading. In normal situation, it should be down to -60dB. In this time, what
mark1 indicates is the insulation of the HIGH side. What mark2 indicates is the inser-
tion loss of HIGH side.
Connect KC901V's output port with duplexer's ANT port, and then connect the
input port to RX port. Then connect the load on the TX port. Adjust the three screws
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