ACCEPTANCE TESTING
7-20 46882/439
Phase modulation
Specification
Range:
0 to 10 radians.
Resolution:
3 digits or 0.01 radians.
Accuracy:
±5% at 1 kHz modulation rate, excluding residual phase modulation.
Bandwidth (3 dB):
100 Hz to 10 kHz.
Distortion:
Less than 3% at 10 radians at 1 kHz modulation rate.
Typically less than 0.5% for deviations up to 1 radian at 1 kHz.
Test equipment
Description Minimum specification Example
Modulation meter
ΦM and FM accuracy ±2% at 1 kHz modulation
frequency
IFR 2305 with
Distortion Option
Phase modulation
Test procedure
(1) Connect the test equipment as shown in Fig. 7-9.
(2) On the UUT set source A to:
[Carrier Freq] 10.5 [MHz]
[RF Level] 0 [dB]
[
Φ
M] [
Φ
M Devn] 10 [rad]
[ΦM ON/OFF]
(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 7-36.
(5
) Repeat (2) to (4) for source B and, if Option 1 is fitted, source C.
Phase modulation flatness
Test procedure
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’s frequency accuracy,
since it is derived from the reference oscillator in the UUT.
(1) Connect the test equipment as shown in Fig. 7-9.
(2) On the UUT set source A to:
[Carrier Freq] 15 [MHz]
[RF Level] 0 [dB]
[
Φ
M] [
Φ
M Devn] 10 [rad]
[ΦM ON/OFF]
(3) On the modulation meter, select CAL, FM, 50 Hz ⇒ 15 kHz LF filter.
(4) Measure the deviation on the modulation meter and calculate the phase modulation using
the formula:
ΦM = FM dev
(Hz)
mod freq (Hz)
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General