Measurements and Results
R&S
®
FSVA3000/ R&S
®
FSV3000
288
User Manual 1178.8520.02 ─ 01
The maximum harmonic distortion is obtained if the level of the harmonic equals the
intrinsic noise level of the receiver. The level applied to the mixer, according to (2), is:
At a resolution bandwidth of 10 Hz (noise level -143 dBm, S.H.I. = 40 dBm), the opti-
mum mixer level is – 51.5 dBm. According to (1) a maximum measurable harmonic dis-
tortion of 91.5 dB minus a minimum S/N ratio of 4 dB is obtained.
Detecting the origin of harmonics
If the harmonic emerges from noise sufficiently (approx. >15 dB), it is easy to check (by
changing the RF attenuation) whether the harmonics originate from the DUT or are
generated internally by the signal analyzer. If a harmonic originates from the DUT, its
level remains constant if the RF attenuation is increased by 10 dB. Only the displayed
noise is increased by 10 dB due to the additional attenuation. If the harmonic is exclu-
sively generated by the signal analyzer, the level of the harmonic is reduced by 20 dB
or is lost in noise. If both – the DUT and the signal analyzer – contribute to the har-
monic, the reduction in the harmonic level is correspondingly smaller.
High-sensitivity harmonics measurements
If harmonics have very small levels, the resolution bandwidth required to measure
them must be reduced considerably. The sweep time is, therefore, also increased con-
siderably. In this case, the measurement of individual harmonics is carried out with the
R&S
FSV/A set to a small span. Only the frequency range around the harmonics will
then be measured with a small resolution bandwidth.
Required measurement time
During the harmonics measurement, zero span sweeps are performed at the center
frequency and at each harmonic. The duration of each sweep ( "Harmonic Sweep
Time" ,
SWT
) and the "Number of Harmonics" (n) are defined in the "Harmonic Distor-
tion" configuration dialog box. Thus, the required measurement time for the harmonic
distortion measurement (
Cumulated Measurement Time
,
CMT
) is:
CMT = n*SWT
The required measurement time is indicated as "CMT" in the channel bar.
7.10.3
Harmonic Distortion Results
As a result of the harmonics distortion measurement, the zero span sweeps of all
detected harmonics are shown in the diagram, separated by red display lines. This pro-
vides a very good overview of the measurement.
Harmonic Distortion Measurement
