Tektronix AFG3000 Series - Page 93

Performance Verification
AFG3000 Series Arbitrary/Function Generators Service Manual 4-31
6. Measure and record each level (A
1
to A
7
) to the seventh harmonics of the
20 kHz sine wave.
7. Calculate the each B
1
to B
7
, C
1
to C
7
value and the THD.
8. Verify that the THD is less than 0.2%.
9. (AFG3xx2 only) Repeat steps 2 through 8 for the channel 2 output.
AFG3xxx Measurement
Function Frequency Fundamental
= reference
2nd 3rd 4th 5th 6th 7th
sine 20.00 kHz 20 kHz 40 kHz 60 kHz 80 kHz 100 kHz 120 kHz 140 kHz
reading (dBm) A
1
= A
2
=A
3
= A
4
=A
5
=A
6
=A
7
=
reading – reference
B
n
= A
n
– A
1
(dBc)
B
1
= 0 B
2
=B
3
=B
4
=B
5
=B
6
=B
7
=
C
n
= 10
Bn/20
C
1
= 1 C
2
=C
3
=C
4
=C
5
=C
6
=C
7
=
THD =
Limit
< 0.2%
Sample: reading 1.5 dBm –58.5 dBm –58.5 dBm –63.5 dBm –58.5 dBm –63.5 dBm –63.5 dBm
reading – reference 0 –60 dBm –60 dBm –65 dBm –60 dBm –65 dBm –65 dBm
C
n
= 1.000 0.001 0.001 0.000562 0.001 0.000562 0.000562
0.1987%
Limit
< 0.2%
THD
C
n
2
n2=
∑
C
1
-----------------------=
THD
C
n
2
n2=
∑
C
1
-----------------------=
NOTE. When all the harmonic components are –62dBm or less, the calculation of
THD can be skipped because it is THD<0.2%.