Agilent Technologies 75000 Series C, E1445A Agilent E1445A Service Manual Verification Tests 65

Test 2-9: Total Harmonic Distortion (cont’d)
Test Procedure
1. Reset the AFG:
*RST;*CLS Reset AFG and clear
status registers
2. Set the AFG to output a sine wave with the 10 MHz filter enabled:
VOLT 24DBM Set AFG amplitude
OUTP:FILT:FREQ 10 MHZ Set filter to 10 MHz
OUTP:FILT ON Enable filter
INIT:IMM Initiate wave form
Perform steps 3 - 6 for each frequency listed in Table 2- 9:
3. Set AFG output frequency:
FREQ <frequency> Set frequency
where <frequency> is the value sp ecified in Table 2-9.
4. Set the Spectrum Analyzer ce nter frequency to the output frequency
of the AFG. Measure the peak amplitude of th e fundamental in dBm.
Note the result for use in step 6.
5. Set the Spectrum Analyzer center frequency to the second harmonic (
2 × fundamental frequency ). Measure the peak a mpl itude of the
second harmonic in dBm.
6. Repeat step 5 for third through ninth harmonics. Calcula te tota l
harmonic distortion as shown below:
thd (dBc) = 20 ⋅ log æ
è √
result2 2 + result3 2 + … +result 9 2 ö
ø
where
resultn (volts) = 10 [ (nth Harmonic (dBm) − Fundamental (dBm))/20 ]
Agilent E1445A Service Manual Verification Tests 65