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ACCEPTANCE TESTING
7-24
Amplitude modulation
Specification
Range: 0
to
99.9%
Resolution: 0.1%
Carrier frequency range:
<500 MHz, usable to 1.5 GHz
Bandwidth (1 dB):
DC to 30 kHz (DC coupled)
10 Hz to 30 kHz (AC coupled)
20 Hz to 30 kHz (AC coupled with ALC)
Accuracy:
±
5% of set depth at 1 kHz modulation rate for output levels not
exc10 dBm (
−
22 dBm at combiner output).
Distortion:
For modulation depths up to 80%, less than 2.5% at 1 kHz rate
For modulation depths up to 30%, less than 1.5% at 1 kHz rate
Φ
M on AM:
Typically 0.1 radians at 30% depth at 470 MHz
Test equipment
Description Minimum
specification Example
Modulation meter
AM accuracy
±
1% at 1 kHz modulation frequency
IFR 2305 with
Distortion Option
DVM
DC voltage measurement
Solartron 7150+
50
Ω
load
(termination)
1 W, 50
Ω
nominal impedance, DC to 2.4 GHz
Lucas Weinschel
M1404N
Audio analyzer
Capable of measuring THD of 0.01% from 100 Hz
to 20 kHz
Rhode &
Schwarz UPA3
Function
generator
DC to 30 kHz sine,
±
0.6 dB flatness
HP 3325B
AM depth and distortion
Test procedure
(1) Connect the test equipment as shown in
Fig. 7-8.
(2)
On the UUT set source A to:
[Carr
Freq]
1.5
[MHz]
[RF
Level]
−
4 [dB]
[AM] [AM Depth]
30
[%]
[AM
ON/OFF]
(3)
On the modulation meter, select CAL, AM, 300 Hz
Þ
3.4 kHz LF filter.
(4) Measure the AM accuracy and distortion at the frequencies shown in
Table 7-36
checking
that the results are within specification.
(5)
Set the UUT to
[AM Depth]
80% and repeat (4).
(6) Set the UUT to
[RF Level]
0 dBm and repeat (4) to (5) using
Table 7-37.
(7) Set the UUT to
[RF Level]
+7 dBm and repeat (4) to (5) using
Table 7-38
.
(8) Set the UUT to
[RF Level]
+10 dBm and repeat (4) to (5) using
Table 7-39
.
(9)
Repeat (2) to (8) for source B.