To access the MEASURE menu go to main menu in the vector voltmeter (VVM) application. The MEASURE menu described below is unique to TABLE view.

This technique measures the S11 reflected signal on a component or cable, and depends upon the procedure in which the far end of the cable is deliberately mismatched, either shorted or left open-circuited. This reflects virtually 100% of the input signal, and the phase delay of the measured reflected signal is therefore equal to twice the one-way phase of the cable. Likewise, the cable attenuation is twice the one-way loss. This technique is especially useful for situations in which you must manually create multiple phase matched cables. This would be done by carefully snipping small amounts of cable with a diagonal cutters, perhaps 3 mm at a time, and re-measuring the effect on the 2-way phase. This technique is most often used for cable trimming, but it can also be used to validate the proper electrical length of any low loss DUT. It is most often used with a reference measurement (golden DUT) which is stored into memory, then subsequent DUTs may be measured and compared against the stored reference. As an option, the measurement port may be vector error corrected (via the calibration process) to provide optimal results. This is the simplest and most convenient VVM measurement. Best results are obtained when the DUT loss is < 20 dB. For a very lossy DUT, use the Transmission Measurement type.

Figure: Vector Voltmeter Reflection Measurement shows a block diagram comparison of the test configuration for the Vector Voltmeter instrument method (left) and the and the equivalent measurement capability integrated within the Site Master in VVM mode right) when the MS208xA is used for S11 reflection measurement. The Vector Voltmeter (when equipped with Option 15) contains not only the Vector Voltmeter receiver, but also the signal source and couplers that are necessary for conducting both 1‑port measurements at a selected CW frequency.

While phase sensitive cabling is used primarily in lower frequency applications that are typical in air navigation systems such as VOR (VHF Omnirange), the Option 15 software VVM procedures are applicable for the entire frequency coverage of the Vector Voltmeter.

Refers to the reflection S-parameter (S11) measured at Port 1 of the Vector Voltmeter. It quantifies how much of an incident signal is reflected back due to impedance mismatch at the port.

S11 can be defined as:

where ZLis the load impedance and Z0 is the characteristic impedance of the system (usually 50Ω)

It is the length of a transmission line or cable measured in terms of the signal wavelength at a specific frequency. It accounts for the phase shift introduced by the length of the line.

The electrical length can be expressed in degrees and is calculated as:

where d is the physical length of the line and λ is the wavelength of the signal.

This technique uses the VVM function in a straightforward manner with its 2‑port setup. The transmission response of the DUT is measured from port 1 to port 2. The DUT amplitude and phase shift are measured by the highly sensitive port 2 receiver. The high dynamic range of this measurement is ideal when the DUT loss is high.

Figure: Vector Voltmeter Port 1–>2 Transmission Measurement shows a block diagram comparison of the test configuration for the Vector Voltmeter instrument method (left) and the equivalent measurement capability integrated within the Site Master in VVM mode (right) when the MS2085A/89A is used for a transmission measurement.

The S21 quantifies how much of the incident signal at Port 1 is transmitted to Port 2. S21 is defined as:

Where Vin is the voltage at Port 1 and Vout is the voltage at Port 2.

For Reflection or Transmission measurements, the MS2085A/89A VVM function can replace the entire setup of source, VVM, and couplers, as shown in Figure: Vector Voltmeter Reflection Measurement and Figure: Vector Voltmeter Port 1–>2 Transmission Measurement. If the measurement setup still requires the use of an external source and couplers, however, then the MS2085A/89A VVM function can replace only the original Vector Voltmeter by using the A/B or B/A measurement selection. The B/A setup is shown in Figure: Vector Voltmeter B/A Measurement with External CW Source with the traditional Vector Voltmeter instrument method (left) and the equivalent measurement using the Site Master in VVM mode (right). For these measurements, the reference signal is received on one port of the MS2085A/89A (Port 1 for B/A and Port 2 for A/B) while the signal transmitted through or reflected from the DUT is received on the other port.

B/A Measurement

 

A/B ratio refers to the comparison of two input signals (often labeled as Signal A and Signal B). It can be expressed in terms of ratio of the amplitude magnitude and phase difference of the two signals.

The A/B receiver ratio can be expressed as:

Wherein, A and B are magnitudes of signals |A| and |B|, and (ΦA and ΦB) are their respective phases.

B/A ratio refers to the comparison of two input signals (often labeled as Signal B and Signal A). It can be expressed in terms of ratio of the amplitude magnitude and phase difference of the two signals.

The B/A receiver ratio can be expressed as:

 

The MS2085A/89A in VVM mode can be used to measure the two ports of a splitter and compare them.

 

 

 

 

Often, absolute phase measurement of a DUT (cable in the following example) is not as important as the phase relationships among multiple DUTs. For the following example application, the Vector Voltmeter is used to make relative phase measurements.

The operations for relative measurements are described in the following steps.

If you are making many measurements, the display format can be set to Table. Refer to This completes the procedure for relative measurements..

This completes the procedure for relative measurements.

The Vector Voltmeter supports four different measurement formats such as Log Magnitude/Phase, Linear Magnitude/Phase, Voltage Standing Wave Ratio (VSWR) and Impedance, to facilitate the easier interpretation of the voltage levels and phase relationships in electrical grids, for example.

The magnitude of the voltage is expressed on a logarithmic scale and usually measured in dB. The Phase angle of the voltage is measured relative to a reference signal, typically expressed in degrees, as shown in Figure: Log Mag/Phase Measurement Format.

The magnitude of the voltage is expressed in linear amplitude, without any logarithmic transformation. The phase angle of the voltage is measured relative to a reference signal, typically expressed in degrees, as shown in the Figure: Linear Mag/Phase Measurement Format.

The Voltage Standing Wave Ratio (VSWR) measurement format is essential for assessing the efficiency of transmission lines and antennas. VSWR indicates how well a load is matched to a transmission line, with implications for signal integrity and power transmission.The VSWR displays the ratio in the upper window only as shown in Figure: VSWR Measurement Format.

The impedance measurement format in a vector voltmeter provides essential data on how a circuit or device interacts with AC signals. By measuring voltage, current, and phase relationships, it allows for the calculation of complex impedance, which is critical for optimizing circuit performance in various applications. The Impedance measurement results are displayed as real impedance in the upper window, and as imaginary impedance in the lower window as shown in the Figure: Impedance Measurement Format.