Atec Rohde-Schwarz-UPL - Manual (Page 6)

6 Audio Analyzer UPL
Fig. 8: Tolerance curves enable fast go/nogo tests
Spectrum analysis
With its FFT analyzer, UPL is also capa-
ble of spectrum analysis. The number of
samples for fast Fourier transform can
be selected between 256 and 16k in
binary steps (Fig. 5). A special feature
is zoom FFT. The signal to be measured
is digitally preprocessed to increase the
frequency resolution by a factor of 2 to
128 over a selectable range. In this
way, a maximum resolution of 0.05 Hz
is attained. It should be emphasized
that this is not just a scale expansion
but the measurement is really made at
a higher resolution (Fig. 6).
Programmable filters
The filters of UPL are software-imple-
mented so that the user can define any
number of filters. The most common
weighting filters are provided as
standard. Further filters can be pro-
grammed in a few seconds by enter-
ing the type (lowpass, highpass, band-
pass, bandstop, notch, third octave or
octave), frequency and attenuation
(Fig. 7). The instrument’s open archi-
tecture shows its strength in particular
where special requirements have to be
met: special filters can be imple-
mented using commercial filter design
programs. The data are transferred to
UPL and the created filter is looped
into the signal path.
A variety of sweep functions
For continuous variation of the test
signals, UPL offers amplitude and fre-
quency sweeps and for bursts addi-
tionally sweeps of interval and on-
time. Sweeps are defined either by
means of a table or via parameters
such as start value, number of steps,
linear/ log stepping or time interval. It
is also possible to sweep two variab-
les simultaneously.
In measurements of external signals,
these can be used for analyzer sweeps
(external sweeps). Many different start
conditions can be set, allowing mea-
surements to be triggered by a variety
of events. Results will be stable even
for DUTs with unknown or unstable
transient response thanks to the
settling function.
Fig. 7: Filters can be defined by entering just a few
parameters
All-in package
Fig. 5: FFT spectrum of two-tone signal shown on full screen
Fig. 6: With the zoom FFT function, sidebands spaced only a
few hertz from the signal can be displayed