ACCEPTANCE TESTING
7-21
Phase modulation
Specification
Range:
0 to 10 radians
Resolution:
3 digits or 0.01 radians
Bandwidth (3 dB):
100 Hz to 10 kHz
Accuracy:
±4% at 1 kHz modulation rate
Distortion:
Less than 3% at 10 radians at 1 kHz modulation rate
Test equipment
Description Minimum specification Example
Modulation meter
ΦM and FM accuracy ±2% at 1 kHz modulation
frequency
Aeroflex 2305
with distortion
option
Phase modulation
Test procedure
(1) Connect the test equipment as shown in Fig. 7-8.
(2) On the UUT set:
[CARR FREQ] 10.5 [MHz]
[RF LEVEL] 0 [dB]
[MENU] 20 [ENTER]
The UUT enters the Modulation Mode menu.
Select
Φ
M int using [NEXT]
[MOD] 10 [rad]
[SOURCE ON/OFF] (to enable modulation source)
[MOD ON/OFF] (to enable modulation)
(3) On the modulation meter, select CAL, ΦM.
(4) Measure the ΦM accuracy and distortion, checking that the results are within the
specification shown in Table 7-28.
Phase modulation flatness
Test procedure
(1) Connect the test equipment as shown in Fig. 7-8.
For this test, the phase modulation figures are calculated from readings taken with the
modulation meter set to FM. No allowances need to be made for the modulation source
frequency accuracy since it is derived from the reference oscillator in the UUT.
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