Anritsu Rubidium MG362 1A Series, Руководство по обслуживанию

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Performance Verification 4-14 FM Flatness Tests
MG362x1A MM PN: 10370-10386 Rev. B 4-41
To measure FM flatness and 3 dB BW within the same test, FSWP phase demod is used instead of FM demod,
as traceability of the FSWP phase demod function is not limited to mod rates
≤ 1 MHz. FM deviation for the
test is set at 2 MHz so 3.3*(FM dev 10 MHz max rate) stays within the chosen 40 MHz demod BW. The
lowest mod rate used is 1 kHz, which at 2 MHz deviation gives mod index = 2000, which is within the FSWP
max limit of 5000 radians. RMS phase deviation, rather than peak, is measured to reduce noise sensitivity.
From the RMS phase deviation measurement of sinusoidal FM:
FM mod index = (peak phase deviation) = sqrt(2)*(RMS phase deviation)
FM deviation = (mod index)*(mod rate)
Mod rate is precisely known, so FM deviation can be accurately calculated.
FM flatness dB = 20*log((FM deviation)/(FM deviation at 1 kHz rate))
Measurement Uncertainties and Test Limits:
The following formulas are used to generate the test limits in Table 4-6 .
Mod index at 2 MHz peak (sinusoidal) FM deviation = (Peak FM deviation)/(2 MHz)
FSWP phase demod uncertainty, %, i.e. “demod%unc” = 0.02*(1+mod index)/(mod index)
FSWP demod flatness uncertainty, dB, relative to 1 kHz:
demod_flat_unc_dB = 20*LOG(1+SQRT((demod%unc)^2+(demod%unc at 1 kHz)^2)/100)
Func Gen flatness (spec) relative to 1 kHz rate = 0.1 dB to < 100 kHz, 0.15 dB to < 5 MHz, 0.3 dB to < 20 MHz.
Total uncertainty dB = sqrt((demod_flat_unc_dB)^2 + (func gen flatness dB)^2)
DUT margin = 1 % = 0.086 dB margin for DUT variation
1 dB test limit = 1 dB – (Total uncertainty dB) – (DUT margin dB) Record the value in
Table 4-6 .
–1 dB test limit = –1*(1 dB test limit)
3 dB test limit = 2 dB+(1 dB test limit)
–3 dB test limit = –1* (3 dB test limit)
Measured FM deviations that differ considerably from the 2 MHz target deviation will cause FSWP demod
uncertainty to vary somewhat from the table value, but the effect on test limits is negligible.
Measurement Uncertainties and Test Limits Table - for the Ext Low Noise FM flatness test is shown in
Table 4-6 .
Table 4-6.
Ext Low Noise FM Flatness Test
mod rate
Hz
mod
index at 2
MHz pk
dev FSWP
phase
demod
unc %
FSWP
unc vs.
1kHz dB
func gen
flat
vs.1kHz
dB
total unc
dB
1dB
test
limit dB
–1dB
test
limit,
dB
3dB
test
limit dB –3dB
test
limit dB
1.00E+03 2.00E+03 0.02 0 0 0 n/a n/a
3.00E+03 6.67E+02 0.02 0.002 0.10 0.10 0.81 –0.81
1.00E+04 2.00E+02 0.02 0.002 0.10 0.10 0.81 –0.81
3.00E+04 6.67E+01 0.02 0.002 0.10 0.10 0.81 –0.81
5.00E+04 4.00E+01 0.02 0.002 0.10 0.10 0.81 –0.81
7.00E+04 2.86E+01 0.02 0.003 0.10 0.10 0.81 –0.81
1.00E+05 2.00E+01 0.02 0.003 0.15 0.15 0.76 –0.76
1.50E+05 1.33E+01 0.02 0.003 0.15 0.15 0.76 –0.76