PowerXpert™ Help : Verifying MA241xxA, MA242x8A Performance : VSWR Pretest
VSWR Pretest
The uncertainty of the VSWR test equipment will affect actual measurement values.
Test Procedure
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.
Before connecting the power sensor to a another device, read the Instrument Care and Preventive Maintenance.
Using required equipment suggested in Table: Required Equipment for MA24108A, MA24118A, MA24126A, follow the manufacturer’s S11 (input return loss) calibration procedure to perform calibration on the network analyzer. Connect the power sensor to the network analyzer test port and measure power sensor input match. Typically, return loss are expressed in dB, which can be interconverted to Reflection coefficient and VSWR as follows:
ρ = 10–RL/20
RL = –20logρ
VSWR = (1 + ρ) / (1 – ρ)
ρ = (VSWR –1) / (VSWR+1)
RL = Return Loss in dB
ρ = Magnitude of the Reflection Coefficient
VSWR = Voltage Standing Wave Ratio
Record the measured data into Table: VSWR Pretest Measurement Result under the Actual Measurement column. The Actual Measurement should be smaller than the Maximum Reflection coefficient. The Maximum Reflection Coefficient is equal to 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: VSWR Pretest Measurement Result, then the sensor is damaged and it is not necessary to perform further testing.
VSWR Pretest Measurement Result
Reflection Coefficient Uncertainty
Maximum Reflection Coefficient
Actual Measurement
10 MHz to 50 MHz
0.310 + 0.013 = 0.323
50 MHz to 150 MHz
0.078 + 0.013 = 0.091
150 MHz to 2 GHz
0.057 + 0.013 = 0.070
2 GHz to 12 GHz
0.099 + 0.020 = 0.119
12 GHz to 18 GHz
0.111 + 0.020 = 0.131
18 GHz to 26 GHz
0.149 + 0.025 = 0.174