Amplitude Modulation Test - HP 8340B Manual

4-15. AMPLITUDE MODULATION TEST

Specification
The following specifications apply when the HP 8340B/41B are internally leveled, for waveforms
whose envelope peak is at least 1 dB below maximum specified power. Unless noted pulse modula-
tion must be OFF; however, the HP 83408/418 are capable of simultaneous amplitude and pulse
modulation. See Section III, Operation.
AM Depth: 0 to 90%
AM Sensitivity at 1 kHz rate and
AM Bandwidth relative to a 1 kHz rate at 30% depth: DC coupled 3 dB point
AM Frequency Response (Flatness) Relative to a 1 kHz rate at 30% depth, DC to 10 kHz:
c0.20 dB
Description
AM sensitivity and accuracy is determined by simulating a modulation signal (i.e., setting the function
generator to a dc voltage). The uninodulated DUT RF output is measured using a power meter. A dc
voltage representing
meter indication should change by:
(dc voltage
20 log (1 4-
The sensitivity and accuracy is tested at several CW frequencies.
The AM frequency response and bandwidth is measured by down converting the DUT's RF frequency
to an IF frequency within the range of the modulation analyzer. The DUT is amplitude modulated using
a function generator. The modulation analyzer is set to indicate 0 dB at the reference modulation
frequency of 1 kHz. The modulation frequency is varied and the flatness is indicated on the modulation
analyzer. The modulating frequency is then set to the bandwidth specification (100 kHz) and the
modulation analyzer should indicate
frequency >100 kHz.
Finally, the function generator output level is increased to obtain >90% modulation depth.
Equipment
Local Oscillator
Modulation Analyzer
Function Generator
Digital Voltmeter
Amplifier
Power Meter
Power Sensor
1. Usable only with HP 8341B OUT.
HP 8340B/41B
Table 4-29. Amplitude Modulation Test Specifications
depth: 100%/Volt
300/o
modulation (±0.3 Vdc) is applied to the DUT's AM input. The power
±300/a
times the dc voltage)))
(0.05
±
—3 dB. this shows that the actual 3 dB point will occur at a
>
±
5O/o
100 kHz
=
HP 8340A Opt. 001 or any HP 8341A/B1
Performance Tests
HP 8901A
HP 3325A
HP 3455A
HP 8447F
HP 436A
HP 8485A
4-71