4-16.
FM ACCURACY AND FLATNESS
Specification
Table 4-30.
Frequency Modulation Specifications
1 Band 4 only applies to the HP 8340B
FM Accuracy Description
FM Accuracy is measured by observing the modulated RF carrier on a spectrum analyzer. When the
modulation index (Peak Deviation divided by Modulation Rate) is set to exactly 2.404, the power in the
carrier will be at zero. This is called a Bessel Null.
Once the carrier has been nulled, the Peak Deviation is known precisely since the Modulation Rate is
synthesized. Since the Peak Deviation is known, the FM input voltage can be measured to calculate
the FM input sensitivity (1 or 10 MHz/V nominally). The error from nominal is expressed as a percent
and is the FM accuracy. This is measured at a 100 kHz rate.
Equipment
Spectrum Analyzer
HP 8566B
Digital Voltmeter
HP 3456A
Function Generator
HP 3325A
Adapters:
APC 3.5(f) to TYPE N(in)
HP P/N 12S0-1744
(1 required if DUT is HP 8340B) (2 required if DUT is HP 8341 B)
APC 3.S (f) to APC 3.S (f)
HP P/N S061-S311
(1 required if DUT is HP 834GB)
BNC(f) to dual banana
HP P/N 1251 -2277
BNC Tee (in) (f) (f)
HP P/N 12S0.0781
Cables:
Semi-Rigid, (SMA male to SMA male)
HP P/N 08340-20124
BNC
(in)
to BNC
(in)
(2 required)
HP P/N 8120-8140
Performance Tests
FREQUENCY MODULATION
Modulation Rate: 50 kHz to 10 MHz (3 dB Bandwidth)
Peak Deviation:
Bands 0,1:
The lesser of 10
MHz or 5
x modulation rate
Band 2:
The lesser of 10 MHz or 10 x modulation rate
Band 3:
The lesser of 10 MHz or 15 x modulation rate
Band
41:
The lesser of 10 MHz or 20 x modulation rate
Deviation Accuracy (at 100 kHz rate):
±
100/c
Sensitivity: 1 MHz/V and 10 MHz/V
HP 8340B/41B
4-75