Before conducting a measurement in VVM mode, set an appropriate CW frequency and perform a calibration. During calibration, choose between a 1‑port or 2‑port calibration depending upon whether return or insertion type measurements (respectively) are desired.
The choice of whether to use a 1-port or a 2-port measurement is usually dictated by the physical site configuration. If the DUT (device under test) is compact, such as cables or amplifiers or filters, then the 2-port measurement may be used because both ends are available near the Vector Voltmeter. If a cable is already installed permanently, then the 1-port methods are indicated because only the one end of the DUT is convenient to the test port.
When making a 1‑port connection to the DUT, select the Return measurement type and perform a 1‑port calibration. When making a 2‑port connection to the DUT, select the Insertion measurement type and perform a 2‑port calibration. The following paragraphs further explain these steps.
How the VVM Function Works
The Vector Voltmeter supports 6 measurement types such as: 1-Port Reflection/Electrical Length, 1-Port Transmission, A/B (Port 1/Port 2), B/A (Port 2/Port 1) Receiver Ratio, A and B. With Option 15 in the MS2085A/89A, you can measure relative magnitude and phase of a DUT either directly (using the built-in source and couplers) or as a ratio function (A/B or B/A) using appropriate external accessories such as a CW signal source and either a power splitter or a coupler. Direct measurements can be 1-port (reflection) or 2-port (transmission) and may also be vector error corrected, thereby providing absolute measured values versus relative measured values. Option 15 is a stand-alone option in the MS2085A/89A and does not require the VNA Mode (Option 904/906) to provide full A/B and B/A ratio capability. All measurements made with Option15 are based on CW signals. They are not swept frequency measurements.