ETTC'2003 - SEE

3. NEW METHOD DEVELOPPED FOR IOT SATELLITE GAIN
FREQUENCY RESPONSE MEASUREMENT
The frequency response is measured by performing relative downlink power
measurement in the linear region of TWTA for each frequency of selected
channel.
An uplink carrier, with about 10 dB IBO, is transmitted to the spacecraft at
channel centre frequency (CCF). The received power level is measured directly
with a spectrum analyser (ASA).
The channel center frequency is used as the reference measurement
At each frequency step in the band, the uplink power is adjusted at the same
level corresponding to the back off condition, between each frequency step, the
uplink frequency signal is made at CCF to note the fluctuation of the reference
point.
The following Figure 4 presents the processing methods:
relative Level (dB)
Figure 4 Measurement processing for the new method
3.1 Measurement processing
Preparation
Measurement processing proposed method
-1,6 -1,4 -1,2 -1 -0,8 -0,6 -0,4 -0,2 0 0,2 0,4
0,4
N2
N4
Frequency Offset (MHz)
N3
N1
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0,3
0,2
0,1
0
-0,1
-0,2
-0,3
-0,4
-0,5
-0,6
measurement in band
center frequency correction