What is VVM?
A VVM (Vector Voltmeter) is a precision electronic instrument that measures the amplitude (voltage) and phase relationship between two input signals at the same frequency. By providing both magnitude and phase information, a VVM enables vector characterisation of RF components, networks, and antennas. While largely superseded by modern vector network analysers (VNA) for most applications, VVM-type measurements remain relevant in specific calibration and antenna measurement scenarios.
How Does VVM Work?
A VVM measures two input signals simultaneously and reports: the voltage amplitude of each signal (in dBm or mV), and the phase difference between them (in degrees). This is achieved using synchronous detection (homodyne or heterodyne) referenced to one of the input signals. The VVM’s ability to measure phase with high accuracy (typically ±1° or better) makes it valuable for characterising transmission line phase shifts, antenna element phase calibration, and reflection coefficient measurements. In modern practice, VNA instruments provide equivalent functionality with greater automation and wider frequency coverage, but the VVM concept underlies many calibration and measurement techniques.
Use Cases
Antenna phase calibration, transmission line phase measurement, reflection coefficient measurement, RF component characterisation, and interferometric measurement systems.
3GPP / Standards Reference
IEEE Std 1658 (Terminology for vector measurements), applicable metrology standards
Related Terms
VSWR | DUT | EIRP | OTA | Phased array antenna
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