Deepace KC901M User Manual page 28

influences from the coax on the result. In such cases, users can "wipe out" the cable
by inputting the cable's length into the instrument to get the antenna's RF
parameters.
There are two items in FUNC menu, which are "Cable Length" and "Cable Loss".
Cable length is the actual length of the cable divided by the velocity coefficient. With
cable length, cable loss can be predicted according to the loss per unit length which is
provided by cable technical manual.
Both two items above are the one -way -travel parameters.
The operation of cable canceling is only suitable on low frequency, for instance,
under 30MHz. Thus as long as permitted, users are highly suggested to do the user
calibration on the end of the cable so that the instrument can remove the cable's
influences precisely.
4.2.3 Antenna Impedance Measurement
KC901M can calculate antenna's impedance by testing RF signal, amplitude
differences of reflection signal and the phase differences. Since amplitude and phase
differences are related with the feeder line, the user calibration must be performed
on the end of the feeder line unless the antenna connects to instrument directly.
As for the antenna based of the PCB, if there is no coaxial interface, users can
disconnect the antenna from the PCB, and then connect the thin coaxial cable to the
instrument. Perform calibration before any measurement. Follow the instruction by
the screen to operate an open/short circuit at the end of the coaxial cable accordingly.
Then skip the load calibration (SKIP).
Antenna's installation environment has a great impact on antenna's impedance.
For the sake of a more accurate measurement, make sure the antenna system setup
is as close to the application environment as possible. Antennas installed on devices
such as handheld device and routers are integrated with the devices' metallic
conductive casing, thus they should be tested with the case. For example, to test the
antenna of the router, the router ant's host device case should be tested together,
and the original coax need to be disconnected from router's PCB for the antenna. The
end of the testing cable, which is near the antenna, needs to go through the toroid
ring. During the calibration, make sure that this cable is included.
Under the low frequency, if it's not able to do the calibration on the cable, user
can set cable length in FUNC menu to remove its influence. But it is not applicable to
the occasion when the frequency is relatively high (for example, 2400MHz).
4.2.4 Simple Measurement of Antenna's Gain and Antenna Pattern
KC901M can test antenna's horizontal pattern or the front-to-back ratio with S21
(or insertion loss) function with another set of antenna; it can even test the antenna
gain adding one more set of antenna whose gain is known.
Measurement environment: RF anechoic Chamber or standard measurement
site. For engineering measurement, choose somewhere open-air and flat, with the
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