Ceyear 3943B, Руководство по эксплуатации

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8 Technical indicators and testing methods
8.5 Performance characteristics test
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signal generator until the audio analyzer shows a stable SINAD value of about 30 dB, reduce the signal
power until the SINAD value drops to 12 dB, and record the corresponding power value read out from
the signal generator at this time in the auxiliary table B.7. power value read on the signal generator at
this time.
d) Recording and data processing
The test results recorded in the auxiliary table B.7 are recorded in the functional performance test record
table A.1 as a summary of AM demodulation sensitivity for the corresponding band.
8.5.1.8 FM demodulation sensitivity
a) Description of the test items
This test is to examine the FM audio demodulation sensitivity of the device to be tested, using the ITU-R
SM.1840 proposal method. The device to be tested has FM demodulation function, providing a total of
34 demodulation bandwidths in the range of 100Hz to 20MHz. This test uses a synthesized signal
generator to generate an FM signal, the device to be tested performs FM demodulation of the signal, and
then tests the demodulated signal output from the headphone interface of the device to be tested.
b) Test diagram and test instruments and equipment
Synthetic Signal Generator ....................................... Recommend 1464/E8257D
Audio analyzer ........................................... Recommend U8903A/U8903B
Fig. 8.8 Schematic diagram of FM demodulation sensitivity test
c) Test procedure
1) Connect the test equipment according to Fig. 8.8, the equipment to be tested and the synthesized
signal generator common time base; the headphone interface of the equipment to be tested is
connected to the input channel interface of the audio analyzer.
2) According to the performance test auxiliary table B.8 performance test form of the test frequency set
synthetic signal generator frequency, power -70dBm, select FM modulation, set the modulation rate
1kHz, frequency bias 5kHz, when the demodulation frequency is not greater than 30MHz, set the
frequency bias 3kHz.
3) Reset the device to be tested. Set the device to be tested as fixed frequency reception mode (FFM),
set the center frequency according to the test frequency of auxiliary table B.8, set the frequency width to
50kHz, demodulation mode to FM, demodulation bandwidth to 15kHz, when the demodulation frequency
is not greater than 30MHz, set the demodulation bandwidth to 9kHz, attenuator off and audio output on.
4) Select the analysis channel of the audio analyzer, set the measurement function of Function1 to
frequency, set the measurement function of Function2 to "SINAD" mode, set the weighting option of the
filter function (Filter) in the measurement configuration (Meas. Weighting) option in the filter function
(Filter) of the measurement configuration (Meas. Config) is set to "CCITT", adjust the output power of the
signal generator until the audio analyzer shows a stable SINAD value of about 30 dB, reduce the signal
power until the SINAD value drops to 20 dB, and record the corresponding power value read out from
the signal generator at this time in the auxiliary table B.8. power value read on the signal generator at
this time.
d) Recording and data processing