Video Bandwidth (VBW) Measurements

Overview

Concept

Video Bandwidth (VBW) is an important Figure Of Merit for modern RF amplifier design. It represents the frequency spacing at which the IMDs are unbalanced. VBW defines the amplifier ability to decouple the DC and the modulated frequency. Higher the VBW is, wider the instantaneous signal bandwidth can be. Maximizing VBW and increasing the decoupling band allows to decrease the drain voltage fluctuation (Low Frequency Memory effect) leading to an improvement of the DPD efficiency. VBW characterization is critical to evaluate the low frequency memory effect related to the biasing circuit.

During this measurement, the 2-tones spacing increases while maintaining a constant and balanced input power.

Finally the C/I_n will be analyzed in order to highlight the low frequency resonance.

Requirements

Available measurements are linked to the Schematic configuration and the selected Calibrations. In order to get access to Video Bandwidth measurements, ONE of the following configurations must be respected:

Vector Network Analyzer needs to be enabled in the Schematic
1-Port Enhanced Calibration or Full 2-Ports & Absolute Power Calibration needs to be enabled
OR
Scalar Setup including RF Source, two (2) or three (3) Power Meter and Vector Signal Analyzer
Scalar Calibration using 2 Power Sensors or Scalar Calibration using 3 Power Sensors needs to be enabled.

To run Video Bandwidth measurements, the bench must be correctly set and calibrated. Once these steps are done, it's possible to initialize the system ( ) and access VBW tab:

Note: If the Schematic is Composed of a Vector Network Analyzer, two (2) or three (3) Power Meter, and a Vector Signal Analyzer and both a Scalar Calibration and Vectorial VNA Calibration are selected, IQSTAR will then automatically choose the Vector Network Analyzer to perform the 2-Tone measurements.