Chapter 2 59
One-Button Measurement Functions
MEASURE (Spectrum Analysis Mode)
One-Button Measurement Functions
When a DVB-T radio standard is selected, this measurement will also compare the input
signal against a pre-defined spectrum mask. The mask amplitudes defined in the DVB-T
specification (ETSI EN 300 744 V1.4.1) range from 0 dB to 100 dB. This is for power
measured in a 4kHz bandwidth therefore an adjustment to these values will need to be
made as the measurement is made in a 7.61MHz bandwidth.
The measurement makes two sweeps, one in a 4kHz bandwidth and one in a 7.61MHz
bandwidth, then computes the difference between the two. This value will be used to
adjust the mask settings. As this value is calculated as part of the measurement setup, it is
expected that the DVB-T signal to be measured will be present prior to the standard being
selected. The mask will be positioned relative to the power measured in the 7.61MHz
bandwidth. The pass/fail indicator will be used to determine if the input signal exceeds the
mask or not.
If the current span setting is narrower than the mask width, the mask will not be
displayed and the message 10191 displayed in error que. Increase the span to at least the
mask width to display the mask. When the mask is not displayed, the pass/fail
functionality will not be executed therefore no pass/fail flag will be displayed.
To ensure accuracy this measurement requires a specific minimum Sweep Point to Span
ratio. This is calculated using; Sweep Points = Span / (Closest Mask Breakpoint / 2), then
rounded off.
For DVB-T measurements using 24 MHz Span, the number of Sweep Points is 2001. If the
Sweep Point to Span ratio is changed to a value less than the value obtained using the
above algorithm, the message 10192 is then displayed, although the measurement is still
made using the new sweep point to span ratio.
Key Path: MEASURE
Remote Command:
Remote Command Notes: The main channel power is returned in the current amplitude
units, and the density value is returned in current amplitude units/Hz
Measurement Results Available
Command Results Returned
:CONFigure:CHPower
:INITiate:CHPower
Not Applicable
:FETCh:CHPower?
:MEASure:CHPower?
:READ:CHPower?
Returns two values that correspond to the Channel
Power and Power Spectral Density.
:FETCh:CHPower:CHPower?
:MEASure:CHPower:CHPower?
:READ:CHPower:CHPower?
Returns a single value that corresponds to the Channel
Power.
:FETCh:CHPower:DENSity?
:MEASure:CHPower:DENSity?
:READ:CHPower:DENSity?
Returns a single value that corresponds to the Power
Spectral Density.