Common Measurement Methods; Quick Adjustment Of Duplexer - Deepace KC901M User 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, KC901M can provide an operation range better than 95dB. User can
adjust the duplexer into the best state under its monitoring.
Prepared accessories: a 50Ω load, 2 RF cables, necessary RF adaptors
Fixing KC901M on the workbench
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 adjust to Low Speed; or the insertion loss mode can work as well.
Take band trap theory's six-cavity duplexer as an example to introduce the
adjusting steps.
Set KC901M to S21 and then set its center and span so that the frequency range
covers the original and the new frequencies of the duplexer. AMP can be set as 0dB or
+10dB (AMP and ordinate range can be switched according to the curve's position.).
After turning on the system calibration, move mark1 and mark2 nearby duplexer's
new receiver frequency and transmitter frequency.
To begin with, measure the insertion loss of the RF cable (S21); slightly shake the
cable and adaptor, and see if the curve shakes as well: if it does, double check the
contact point. Cable's insertion loss should be neglectably small and be steady as well.
Choose a cable of adequate quality. User can hang the cable in the air to check the
position of instrument's noise floor. In 450MHz, it should be at least up to -90dB
though, better below -100dB.
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
instrument's another port to duplexer's ANT (antenna) port. Finally, connect the
dummy load to the remaining RX port (usually noted as low)(Chart 4-1).
- 23 -