4-15 FM Deviation Accuracy Tests
Performance Verification
4-48
PN: 10370-10386 Rev. B
MG362x1A MM
Int Low Noise FM Accuracy
(Do this test if the optional internal modulation source is installed)
FM deviation measurement is done the same as for the Ext Low Noise FM Accuracy test. Uncertainty of the
FSWP RMS Phase Deviation measurement at mod index = 2000 is 0.020 %. At 1 kHz mod rate, uncertainty of
the DUT deviation setting is determined primarily by control resolution of digital frequency synthesis circuits,
which is roughly 0.01 %. So total uncertainty is roughly 0.022 %. DUT gain drift at 1 kHz mod rate is
negligible, but allow about 0.5 % margin. So a ±2.0 % sales spec would have a test limit of ±1.5 %.
Test Setup
Connect equipment as shown in
FSWP:
If PM Time Domain window is not already displayed, then: Tab Analog Demod, Meas Config / Display
Config / drag “PM Time Domain” to screen center. This will replace FM measurement with Phase Mod
measurement. The “Summary” Display will now show Phase Mod results.
Meas Config / Demod BW 8 MHz, Meas Time = 350 msec.
Demod Config / Demod / AF Coupling = AC
Demod Config / Demod / Unit / Phase Unit = rad
Scale Config = 500 rad/div.
Trace Config:
Trace 1 Clear/Write, Linear, Smoothing = 1 %.
Trigger button:
Set “PM Offline” as the trigger source.
External Function Generator:
Channel OFF
External DVM:
Not used.
MG362x1A:
Low Noise FM mode, Int FM, DC Coupled, FM Deviation = 2 MHz, FM Rate = 1 kHz, FM ON.
Test Procedure
1.
Wait 2sec for FSWP to complete the RMS Phase Deviation measurement. Note RMS Phase Deviation
(radians) shown in the FSWP “Summary” window.
2.
Calculate FM Deviation = sqrt(2)*(RMS phase deviation, rad)*(mod rate, Hz). Record this FM deviation
value for the Int LNFM Accuracy test.
3.
Calculate “% Error” = 100*((Calculated FM Deviation)–2 MHz)/(2 MHz)
4.
Record % Error. If % Error is within ±1.5 % report “Pass”, otherwise report “Fail”.
Ext Wide (unlocked) FM Accuracy
FM Deviation sensitivity accuracy is measured at 5 GHz and 10 GHz RF using 100 MHz/V Ext FM setting with
2Vpp 1 kHz sinewave applied to the Ext FM input. Spectrum width is used to measure FM deviation. A DVM
measures amplitude of the external modulation waveform.
Uncertainty of the measurement
SPA frequency markers are used to measure width of the occupied spectrum. There are 1001 frequency points
per span, which gives marker frequency measurement a quantization-related uncertainty that is uniformly
distributed across ±(½ * Span/1000). Delta-marker measurement, which takes the difference between two
markers then has triangularly distributed uncertainty with peak value = ±Span/1000, and stdev =
Span/(1000*sqrt(6)). Uncertainty at 2 stdev is then Span/(500*sqrt(6)). The 250 MHz span used for this test
gives
Δ
marker uncertainty = ±0.204 MHz at 2stdev.
RBW uncertainty is claimed to be 3 % nominal for FSWP. Assume 1 stdev.
2stdev uncertainty would then be 2*(3 % of 3 MHz RBW) = 0.18 MHz.
Total uncertainty of spectrum –3 dB width measurement = RSS(0.204 MHz, 0.18 MHz) = ±0.27 MHz.
Summary of Contents for Rubidium MG362 1A Series
Page 12: ...Contents 10 PN 10370 10386 Rev B MG362x1A MM ...
Page 16: ...1 9 ESD Requirements General Information 1 4 PN 10370 10386 Rev B MG362x1A MM ...
Page 30: ...2 6 RF Deck Assemblies Functional Description 2 14 PN 10370 10386 Rev B MG362x1A MM ...
Page 66: ...3 11 FM and Phase Modulation Calibration Calibration 3 36 PN 10370 10386 Rev B MG362x1A MM ...
Page 292: ...B 5 Self Test Messages Instrument Messages B 8 PN 10370 10386 Rev B MG362x1A MM ...
Page 293: ......
