Aeroflex 2025 - Amplitude Modulation; AM Depth and Distortion

ACCEPTANCE TESTING
7-23
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
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.
ΦM 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
Aeroflex 2305
with distortion
option
DVM DC voltage measurement Solartron 7150+
50 Ω load
(termination)
1 W, 50 Ω nominal impedance, DC to 2.51 GHz
Lucas Weinschel
M1404N
Audio analyzer Capable of measuring THD of 0.01% from 100 Hz
to 20 kHz
Rohde & Schwarz
UPA3
Function
generator
DC to 30 kHz sine, ±0.6 dB flatness
Agilent 3325B
AM depth and distortion
Test procedure
(1) Connect the test equipment as shown in Fig. 7-8.
(2) On the UUT set:
[CARR FREQ] 1.5 [MHz]
[RF LEVEL]
−4 [dB]
[MENU] 20 [ENTER]
The UUT enters the Modulation Mode menu
Select AM int
[MOD] 30 [%]
[SOURCE ON/OFF] (to enable modulation source)
[MOD ON/OFF] (to enable modulation)
(3) On the modulation meter, select CAL, AM, 300 Hz ⇒ 3.4 kHz LF filter.
(4) Measure the AM accuracy and distortion at the frequencies shown in Table 7-30, checking
th
at the results are within specification
(5) Set the UUT to [MOD] 80% and repeat (4).
(6) Set the UUT to [RF LEVEL] 0 dBm and repeat (2) to (5) using Table 7-31.
(7
) Set the UUT to [RF LEVEL] +7 dBm and repeat (2) to (5) using Table 7-32.