Ratios   

The Ratios submenu selects and defines ratios of wave quantities.

Ratios

• b2/a1 Src Port 1, b1/a1 Src Port 1, b2/b1 Src Port 1, and b1/b2 Scr Port 1 select predefined ratios of the standard 2-port wave quantities a1, a2, b1, and b2, to be measured in forward direction with port 1 providing the stimulus signal.

• More Ratios opens a dialog to define and select arbitrary ratios of wave quantities for different detectors and source ports or higher port numbers or frequency offsets. In true differential mode, the dialog also offers ratios of balanced wave quantities.

In contrast to S-parameters, ratios are not system error corrected. A power calibration can be applied to ratios; see Data Flow.

b2/a1 Src Port 1, b1/a1 Src Port 1, b2/b1 Src Port 1, b1/b2 Src Port 1

Select predefined complex ratios of the standard 2-port wave quantities a1, a2, b1, and b2:

The predefined wave quantities are all obtained with the same test set configuration, port 1 providing the stimulus signal (source port 1, forward measurement if the stimulus signal is fed to the input of the DUT).

• b2/a1 Src Port 1 is the ratio of the wave quantities b2 and a1 and corresponds to the S-parameter S21 (forward transmission coefficient).

• b1/a1 Src Port 1 is the ratio of the wave quantities b1 and a1, measured at PORT 1, and corresponds to the S-parameter S11 (input reflection coefficient).

• b2/b1 Src Port 1 is the ratio of the transmitted to the reflected wave quantities in a forward measurement.

• b1/b2 Src Port 1 is the inverse of b2/a1 Src Port 1.

The analyzer can also measure arbitrary ratios for other source ports; see More Ratios.

More Ratios

Opens a dialog to select arbitrary ratios of wave quantities, e.g. for different source ports or higher port numbers. In true differential mode, the dialog also offers ratios of balanced wave quantities.

The notation for ratios and the functionality of the More Ratios dialog is analogous to the definition of S-parameters.

• Numerator selects the type (left pull-down list) and the port number assignment (right pull-down list) of the wave that forms the numerator of the ratio. Ratios of balanced wave quantities are only available if the True Differential Mode is active; see background information below. The input (stimulus) or output (response) port number is selected in the right pull-down list. The range of output and input port numbers depends on the analyzer model.

• Denominator selects the type (left pull-down list) and the port number assignment (right pull-down list) of the wave that forms the denominator of the ratio. The same waves as for the Numerator are available.

• Ratio indicates the selected ratio.

• Source Port contains all analyzer ports or external generators which can be used as a source for the stimulus signal. The list contains all analyzer ports Port 1 to Port n. Generators (Gen 1, Gen 2, ...) must be configured explicitly in the System Configuration – External Generators dialog before they appear in the list.  

• Detector selects the algorithm that is used to calculate the displayed trace from the individual measurement points. In the Max. and RMS detector modes, it is possible to define the detector observation time (Meas. Time) for a single measurement point. The Detector and Meas. Time controls are both unavailable in true differential mode, because only the Normal detector provides consistent phase information.

External generators

Ratios of single-ended and balanced wave quantities

Detector

Selects the algorithm that is used to calculate the displayed measurement points from the raw data. The Detector can be selected in the More S-Parameters, More Ratios and More Wave Quantities dialogs.

The following detectors are available:

• Normal selects the default detector mode where each measurement point is displayed without modification as soon as it is recognized to be valid. The analyzer then proceeds to the next sweep point. Normal detector mode ensures that the measurement is performed at maximum speed and that a meaningful complex result is obtained.  

• AVG collects all valid results at each sweep point during the Meas. Time set in the More S-Parameters,More Ratios or More Wave Quantities dialog and calculates the complex arithmetic mean value of these results. This yields the complex average of the wave quantities or ratios. Averaging tends to remove statistical fluctuations (e.g. noise contributions) from the measured signal.
  The average(AVG) detector is also used for the noise figure measurement.  

R&S ZVA and R&S ZVT analyzers provide the following additional detectors for ratios and wave quantities:

• Peak collects all valid results at each sweep point during the Meas. Time set in the More Ratios or More Wave Quantities dialog and selects the result with the maximum magnitude (maximum power) as the measurement point. Note that the phase is not evaluated in this process so that complex conversions (e. g. the calculation of real and imaginary values) do not really make sense.  

• RMS collects all valid results at each sweep point during the Meas. Time set in the More Ratios or More Wave Quantities dialog and calculates the root mean square (RMS) of the linear magnitude of these results. This yields the magnitude of the measurement point. Note that the phase is not evaluated in this process so that complex conversions (e. g. the calculation of real and imaginary values) do not really make sense.  

The detector settings have an influence on the displayed trace. They do not affect the number of measurement points in a sweep (or in a subset of the sweep range) but may increase the sweep time In the Peak,RMS, and AVG detector settings, the sweep time cannot be smaller than the detector observation time (Meas. Time) set in the More Ratios or More Wave Quantities dialogs. The sweep time can be larger if additional delays are taken into account. Changing the Meas. Time affects the sweep time. On the other hand, increasing the Sweep Time in the Channel – Sweep menu leaves the Meas. Time unchanged. The AVG, Peak, and RMS detector settings appear in the trace line.

Combining different detectors

The analyzer generates a warning if the selected measurement time for AVG, Peak or RMS detectors is too long. At the same time, bit no. 15 in the ...INTegrity:HARDware status register is set. Reduce the measurement time and/or reduce the IF bandwidth until the warning disappears.
A warning also appears if the measurement time for RMS detectors is too short. Increase the measurement time and/or increase the IF bandwidth until the warning disappears.

Measurements at Two Different Frequencies

The More Ratios and More Wave Quantities dialogs provide the wave quantities a1, b1... These wave quantities are measured at the common receiver frequency, which is equal for all ports: If no frequency-converting mode is active, the common receiver frequency is equal to the stimulus frequency of the NWA source (channel base frequency fb).

With option ZVA-K4, Arbitrary Generator and Receiver Frequencies, the network analyzer provides an additional set of "primed" wave quantities a'1, b'1..., to be measured at fixed, but port-specific frequency offsets from the common receiver frequency. Primed wave quantities can also be used to calculate ratios.

The basic and the primed results are measured in two different analyzer paths. The two signals are separated in the digital part of the receiver, after down-conversion of the RF input signal in the first mixer, a low-pass filter stage, and analog/digital conversion. The digital paths contain mixer stages with two independent numerically controlled oscillators NCO 1 and NCO 2. Each of the NCOs converts one signal component to the analyzer frequency.

The port-specific frequency offset between primed and unprimed waves can be set in the Receiver section of the Port Configuration dialog (D Freq a', b').   

Measurement application, bandwidth considerations

The port-specific frequency offset extends the receiver frequency conversion in the Receiver Frequency dialog, which is equal for all analyzer ports.
In remote control, it is possible to define an additional port-specific offset to the basic frequencies; see remote control commands below. The additional offset is not displayed in the Port Configuration dialog. The total frequency offset between primed and basic wave quantities is equal to (D Freq a', b' – D Freq a, b).