R&S SMB Test Procedures
1407.0806.82 1.29 E-5
Internal Modulation Generator
Frequency accuracy
The LF-Generator is integrated into an FPGA clocked with the same reference frequency as the
synthesizer. Therefore, the LF frequency has the same accuracy as the RF and has not to be
m
easured.
Distortions
Test equipment Spectrum analyzer (Table 1-1, item 18)
Test method The fundamental and harmonics of the LF-generator are measured
with the analyzer. The analyzer calculates the Total Harmonic
Distortion with the ‘Harmonic Distortion’ function.
Test setup Connect the spectrum analyzer to the LF socket of the DUT
through a 150 V series resistor. This is necessary, because the LF
output can only drive 200 V loads with very good harmonic
distortion. If the instrument is equipped with a RFBOARD
1406.7207.xx switch the LF Gen output impedance to 600 V and
omit the 150 V series resistor.
Measurement of frequency
settings and distortion
Settings on DUT:
LF Output menu:
LF Gen Voltage 1 V
LF Gen Frequency 1 kHz
Settings of the spectrum analyzer:
RF INPUT DC
AMPT REF LEVEL 10 dBm
FREQ CENTER = LF Gen Frequency
MEAS HARMONIC DISTOR
RF ATTEN MANUAL increase by 10 dB
Read the THD
repeat the measurement at the recommended test frequencies by
changing the DUT LF Gen Frequency and the analyzer center
frequency.
Recommended test
frequencies
100 Hz, 300 Hz, 1 kHz, 3 kHz, 10 kHz, 30 kHz, 100 kHz
Level Accuracy and Frequency response
Test equipment AC voltmeter (Table 1-1, item 14)
Test method The output level of the LF Generator is measured direct with an AC
voltmeter.
Test setup Connect the AC voltmeter to the LF socket of the DUT.
Measurement of Level
Accuracy
Settings on DUT:
LF Output menu:
LF Gen Frequency 1 kHz
set LF Output Voltage to recommended levels and measure the
output level
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