The Power Bandwidth Average menu defines the power of the internal signal source, sets the step attenuators and the IF bandwidths, and configures the sweep average.
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Power defines the power of the internal signal source.
RF Off switches the internal and external power sources off (if checked) or on.
Meas. Bandwidth selects the bandwidth of the IF measurement filter.
Average On activates or de-activates the sweep average. With average on the measurement results are averaged over a selected number of consecutive sweeps (Average Factor).
Average Factor defines the number of consecutive sweeps to be averaged.
Restart Average starts a new average cycle, clearing all previous results and thus eliminating their effect on the new cycle. The new cycle is started as fast as possible; an ongoing sweep is terminated immediately.
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Remote control |
DIAGnostic:SERVice:RFPower |
Opens the numeric entry bar to set the power of the internal signal source (channel power).
The channel power determines the output power at the test ports if a Frequency Sweep, Time Sweep or CW Mode Sweep is active; see info below. The setting has no effect in Power Sweep mode, where the source power is varied over a continuous range.
The selected channel power applies to all source ports
used in the active channel. Use the Port
Configuration
dialog to modify the output power ranges for the individual analyzer ports.
Output power at the test ports
Power sets the output power at the test port that supplies the stimulus for the active channel. The channel power can be varied over a wide dynamic range. This leaves enough flexibility to include an attenuation or gain in the test setup.
The channel power can be modified by the following settings:
The Source section of the Port Configuration dialog provides a port-specific constant power offset (for arbitrary sweeps) and a port and frequency-dependent power slope factor (for frequency sweeps).
A generator (source) power calibration generally modifies the channel power so that Power is equal to the power at the calibrated reference plane.
The Port <port_no> Source Powerdialog gives an overview of all power settings.
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Remote control: |
RF Off switches the internal and external power sources off (if checked) or on. Switching off the RF power helps to prevent overheating of a connected DUT while no measurement results are taken. The exact behavior of RF Off is part of the system configuration; refer to the description of the Power tab.
After the RF power is switched on, the start
of the measurement is delayed by approx. 1 s while the amplifier stages
of the analyzer are allowed to settle. To avoid this delay, reduce the
base channel power setting or turn off the drive ports in the Port
Configuration
dialog instead of using RF Off.
Switching off the internal
RF generator while an external generator is used can improve the measurement
accuracy. RF Off also deactivates
external generators, so you have to use the settings in the Source
section of the Port Configuration
dialog (with option R&S ZVA-K4).
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Remote control: |
Sets the measurement bandwidth of the IF filter. Meas Bandwidth opens a submenu to select bandwidths between 10 Hz and 1 MHz:
Fine Adjust... opens a dialog where you can modify the selected measurement bandwidth and the selectivity of the IF filter.
The numeric entry field shows the last IF filter bandwidth selected. The arrow buttons increment and decrement the bandwidth in 1-2-5 steps for each decade. Entered values between the steps will be rounded up, values exceeding the maximum bandwidth rounded down.
Selectivity selects between two types of IF filters: Filters with Normal selectivity and short settling time, and filters with High selectivity but larger settling time.
The selected bandwidth applies to all filters used in the current channel. This makes sense because the measurement speed is limited by the slowest filter in the channel. In Segmented Frequency sweeps, the bandwidth and selectivity can be set independently for each segment; see Define Segments.
Optimizing the filter settings
A high selectivity and a small filter bandwidth both suppress the noise level around the measurement frequency and thus increase the dynamic range. On the other hand the time needed to acquire a single measurement point increases for small filter bandwidths and high selectivity. For small bandwidths, the filter settling time, which is inversely proportional to the bandwidth, is responsible for the predominant part of the measurement time.
The characteristics of the high selectivity filter makes it particularly suitable for isolating unexpected spurious responses or known mixer products.
In general, the
system error correction is no longer valid after a change of the IF filter
bandwidth. The message Cal? appears
in the trace list.
Optimizing
the measurement speed
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Remote control: |
[SENSe<Ch>:]BANDwidth|BWIDth[:RESolution] |
Opens the numeric entry bar to define the number of consecutive sweeps to be averaged.
An average over several sweeps reduces the influence of random effects in the measurement and therefore minimizes the noise level. The effect increases with the average factor, however, obtaining an averaged result requires several sweeps and therefore increases the measurement time.
In contrast to the sweep
count
(for single sweep mode), averaging is always channel-specific. Both features
are completely independent from each other.
The average factor is also valid for calibration sweeps: The calculation
of system correction data is based on the averaged trace.
Smoothing
is an alternative method of compensating for random effects on the trace
by averaging adjacent measurement points. Compared to the sweep average,
smoothing does not significantly increase the measurement time but can
eliminate narrow peaks and thus produce misleading results.
The sweep average is not frequency selective. To eliminate a spurious signal in the vicinity of the measurement frequency, alternative techniques (e.g. a smaller filter bandwidth) must be used.
The average trace is obtained as follows:
Let c be the Average Factor and assume that n sweeps have been measured since the start of the average cycle (start of the measurement or Restart Average). The following two situations are distinguished:
n < c: At each sweep point, the average trace no. n is calculated from the average trace no. n 1 and the current trace no. n according to the following recurrence:
The average trace represents the arithmetic mean value over all n sweeps.
n > c: At each sweep point, the average trace no. n is calculated from the average trace no. n 1 and the current trace no. n according to:
The formulas hold for Average Factor n = 1 where the average trace becomes equal to the current trace.
Optimizing
the measurement speed
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Remote control: |
[SENSe<Ch>:]AVERage[:STATe]
ON | OFF |
