R&S RTA4000, Руководство пользователя

Страница: 57 / 861

Waveform setup
R&S
®
RTA4000
57 User Manual 1335.7898.02 ─ 08
To reduce noise, you can set a frequency limit. Higher frequencies are removed from
the signal. Limited bandwidth is indicated by "B
W
" in the waveform label.
For analog applications, the highest signal frequency determines the required oscillo-
scope bandwidth. The oscilloscope bandwidth should be at least 3 times higher than
the maximum frequency included in the analog test signal to measure the amplitude
without aliasing.
Most test signals are more complex than a simple sine wave and include several spec-
tral components. A digital signal, for example, is built up of several odd harmonics. For
digital signals, the oscilloscope bandwidth should be at least 5 times higher than the
clock frequency to be measured.
The oscilloscope is not an autonomous system. You need a probe to measure the sig-
nal, and the probe has a limited bandwidth, too. The combination of oscilloscope and
probe creates a system bandwidth. To reduce the effect of the probe on the system
bandwidth, the probe bandwidth should exceed the bandwidth of the oscilloscope, the
recommended factor is 1.5 x oscilloscope bandwidth.
Remote command:
CHANnel<m>:BANDwidth
on page 438
Vertical Scale
Sets the vertical scale in Volts per division to change the displayed amplitude of the
selected waveform. The current value is shown in the waveform label below the grid.
Vertical scale directly affects the resolution of the waveform amplitude. To get the full
resolution of the ADC, set up the waveforms to cover most of the height of the dia-
gram.
Remote command:
CHANnel<m>:SCALe
on page 436
Offset
Sets the offset voltage, which corrects an offset-affected signal. The vertical center of
the selected channel is shifted by the offset value and the signal is repositioned within
the diagram area. To set the offset automatically, use [Autoset].
Use the offset to measure small AC voltages that are overlaid by higher DC voltages.
Unlike AC coupling, the DC part of the signal is not lost with offset setting.
If an active probe is connected, the offset limit is defined by the probe. Refer to the
documentation of the probe for allowed values.
If an active differential probe is connected, set the common-mode offset to compensate
for a common DC voltage applied to both input sockets (referenced to the ground
socket). Thus, you can measure on differential signals with high common mode levels.
You can measure the common mode input voltage using the R&S ProbeMeter.
If you use a R&S RT-ZM modular probe, the "Offset" is the differential offset. The differ-
ential offset is a DC voltage applied between the positive (V
p
) and the negative (V
n
)
input terminal at the probe tip. The common mode offset is set separately in the
"Probe" menu.
Remote command:
CHANnel<m>:OFFSet
on page 437
Vertical setup