VSWR Pretest

The uncertainty of the VSWR test equipment will affect actual measurement values.

Test Procedure

Caution | Do not apply power greater than the power sensor specifications or permanent damage may result. Connect a fixed attenuator to the output connector when power exceeds +20 dBm. |

Caution | Before connecting the power sensor to a another device, read the Instrument Care and Preventive Maintenance. |

Using required equipment suggested in Table: Required Equipment, follow the manufacturer’s S11 (or return loss) calibration procedure to perform calibration on a network analyzer. Connect the power sensor to the network analyzer test port and measure power sensor input match. Typically, matches are measured in terms of return loss in dB. Return loss and magnitude of the reflection coefficient conversion equations are as follows:

ρ = 10–RL/20

RL = –20logρ

where

RL = Return Loss in dB

ρ = Magnitude of the Reflection Coefficient

VSWR and magnitude of the reflection coefficient conversion equations are as follows:

VSWR = (1 + ρ) / (1 – ρ)

ρ = (VSWR – 1) / (VSWR + 1)

where

VSWR = Voltage Standing Wave Ratio

ρ = Magnitude of the Reflection Coefficient

Record the measured data to Table: Pretest Measurement Result in the Actual Measurement column. The Actual Measurement should be smaller than the Maximum Reflection Coefficient. The Maximum Reflection Coefficient is the measurement system uncertainty added to the sensor’s reflection coefficient specification. If the Actual Measurement reflection coefficient is larger than the Maximum Reflection Coefficient, then the power sensor may be defective. If the actual reflection coefficient is significantly larger than the maximum values in Table: Pretest Measurement Result, then the sensor is damaged and it is not necessary to perform further testing.

Frequency | MS4642B Reflection Coefficient Uncertainty | Maximum Reflection Coefficient | Actual Measurement |

350 MHz to 3 GHz | 0.013 | 0.033 + 0.013 = 0.046 | |

3 GHz to 4 GHz | 0.020 | 0.047 + 0.020 = 0.067 |