Chapter 3 95
Making EDGE (with GSM) Measurements
Making the Waveform (Time Domain) Measurement
Make sure the Waveform (Time Domain) measurement is selected under
the
Measure menu. Press the Meas Setup key to access a menu which
allows you to modify the averaging, and trigger source for this
measurement (as described in the “Measurement Setup” section). In
addition, the following parameters can be modified:
•
Sweep Time - This key allows you to select the measurement
acquisition time. It is used to specify the length of the time capture
record. Values between 10 µs and 50 s can be entered, depending
upon the resolution bandwidth setting.
•
Res BW - This key sets the measurement bandwidth. A larger
bandwidth results in a larger number of acquisition points and
reduces the maximum allowed for sweep time. You can enter values
between 10 Hz. and 7.5 MHz.
•
Advanced menu key. This key accesses the features listed below.
Pre-ADC BPF - This key allows you to toggle the pre-ADC
bandpass filter to On or Off states. The pre-ADC bandpass filter
is useful for rejecting nearby signals, so that sensitivity within
the span range can be improved by increasing the ADC range
gain
RBW Filter - This key toggles to select a flat top or a Gaussian
resolution bandwidth filter. A Gaussian filter provides more even
time domain response, particularly for bursts. A flat top filter
provides a flatter bandwidth but is less accurate for pulse
responses. A flat top filter also requires less memory and allows
longer data acquisition times. For most waveform applications,
the Gaussian filter is recommended, and it is the default filter for
waveform measurements.
ADC Range -.Allows you to access the following selection menu to
define one of the following ADC ranging functions:
•
Auto - This key causes the instrument to automatically adjust
the signal range for optimal measurement results.
•
AutoPeak - This key causes the instrument to continuously
seek the highest peak signal.
•
AutoPeakLock - This key causes the instrument to adjust the
range for the highest peak signal it identifies, and retains the
range settings determined by that peak signal, even when the
peak signal is no longer present.
•
Manual - Allows you to access the selection menu: −6 dB, 0 dB,
+6 dB, +12 dB, +18 dB, +24 dB, to set the ADC range level. Also
note that manual ranging is best for CW signals.
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