The Ratios submenu selects and defines ratios of wave quantities.
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.
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.
Remote control: |
CALCulate<Ch>:PARameter:MEASure
"<Trace_Name>", "B2/A1"
| ... Create
new trace and select name and measurement parameter: |
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.
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.
The measurement process for external generators Gen 1, Gen2... in the Source Port list differs fromthe measurement process for internal source ports:
An external generator always represents a permanent signal source that is switched on for all partial measurements. In contrast, an analyzer port is switched off for partial measurements that do not require a source signal. Exception: Internal ports can be configured as permanent sources (see Gen setting in theSourcesection of the Port Configuration dialog).
The external source is measured in the first partial measurement where an internal source is active. This means that no separate partial measurement for the external generator signal is needed. If no internal source is needed at all, the external source is measured in the first partial measurement.
Ratios of single-ended and balanced wave quantities
If a balanced port configuration is selected and the True Differential Mode is active, the left Numerator and Denominator pull-down lists contain the following wave types:
as, bs: Single-ended incident (a) or outgoing (b) wave. To select this wave type, the selected port must be unbalanced. If the port configuration contains no unbalanced ports, the single-ended wave quantities are hidden.
ad, ac, bd, bc: Balanced incident (a) or outgoing (b) waves. d and c distinguish between the differential and common mode; see Wave Quantities and Ratios.
Remote control: |
CALCulate<Ch>:PARameter:MEASure
"<Trace_Name>", "B2/A1" | ... Create
new trace and select name and measurement parameter: |
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:
R&S ZVA and R&S ZVT analyzers provide the following additional detectors for ratios and wave quantities:
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 . The AVG, Peak, and RMS detector settings appear in the trace line.
The detector setting in the More Ratios menu affects the ratio of a numerator and a denominator wave quantity. This does not place any restrictions on the measurement functionality of the analyzer, because ratios can also be formed by measuring the numerator and denominator individually and using the trace functions. A possible application is the comparison of different detector settings for a particular trace.
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.
Remote control: |
CALCulate<Ch>:PARameter:MEASure
"<Trace_Name>", "<Par>"
|
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 second analyzer and the quantities a'1, b'1, a's1, a'c1,... are suited for a comparison of two signals or signal components at different frequencies (two tone signals). Typical examples are:
Measurement of intermodulation products
Adjacent Channel Power (ACP) measurements
The maximum frequency offset between primed and unprimed waves is limited by the cutoff frequency of the analog low-pass filer. The minimum frequency offset is determined by the bandwidth of the digital IF filters (Channel Power Bandwidth Average Meas Bandwidth). It is recommended to use IF filters with high selectivity.
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).
Remote control: |
SENSe<Ch>:FREQuency<Pt>:OFFSet:PWAVes
|