Post on 30-Oct-2015
Kathrein T. Wulff 08/2002
VSWR Calculation
Kathrein-Werke KGRosenheimPO Box 10 04 44Phone:+ 49 (0)8031 184 - 0Fax: +49 (0)8031 184 991antennas.mobilcom@kathrein.dewww.kathrein.de
Torsten Wulff
Kathrein-Werke KGRosenheimGermany
www.kathrein.dePhone: +049 8031 184 - 0
VSWR Calculation
Rule of Thumb Calculation
Advanced Calculation
Conclusion
Site Calculations
Improper Calculation
Adding different VSWR values
Kathrein T. Wulff 08/2002
How to add different VSWRs
VSWR, Antenna1.5
VSWR, Feeder Cable / Jumper Cable1.1
Total VSWR???
VSWR Calculation
Rule of Thumb Calculation
Advanced Calculation
Conclusion
Site Calculations
Improper Calculation
Adding different VSWR values
Kathrein T. Wulff 08/2002
VSWR Calculation
How to add VSWR values
Re-calculate the reflection coefficient out of a given VSWR value
Add two reflection coefficients to recover a new reflection coefficient
Re-calculate VSWR value out of the new reflection coefficient
n
nn VSWR 1
1 - VSWR r +=
21total r r r +=
total
totaltotal r - 1
r 1 VSWR +=
VSWR Calculation
Rule of Thumb Calculation
Advanced Calculation
Conclusion
Site Calculations
Improper Calculation
Adding different VSWR values
Kathrein T. Wulff 08/2002
VSWR Calculation
Which values are required to calculate the overall VSWR of a site installation?
VSWR, Antenna
VSWR, Feeder Cable
Insertion loss, Feeder Cable
VSWR Calculation
Rule of Thumb Calculation
Advanced Calculation
Conclusion
Site Calculations
Improper Calculation
Adding different VSWR values
Kathrein T. Wulff 08/2002
VSWR Calculation
Example of an improper calculation
VSWR, Antenna (1.5)
VSWR, Feeder Cable (1.1)
VSWR 1.1 + VSWR 1.5 = VSWR 1,66 (worst case)This equals a return loss of 12.2 dB
This calculation considers a lossless cable and is incorrect for a site measurement!
VSWR Calculation
Rule of Thumb Calculation
Advanced Calculation
Conclusion
Site Calculations
Improper Calculation
Adding different VSWR values
Kathrein T. Wulff 08/2002
VSWR Calculation
Rule of thumb calculation
VSWR, Antenna (1.5) Cable attenuation 3 dB (one way)
VSWR 1.5 = 14 dB return loss
Total cable attenuation: 2 x 3 dB insertion loss plus 14 dB = 20 dB
20 dB return loss equals a VSWR of 1.22
This calculation considers a lossy cable witha perfect impedance match!
VSWR Calculation
Rule of Thumb Calculation
Advanced Calculation
Conclusion
Site Calculations
Improper Calculation
Adding different VSWR values
Kathrein T. Wulff 08/2002
VSWR Calculation
Example of an advanced site calculation
VSWR, Antenna (1.5)
VSWR, Cable Connector (1.1)
Jumper cable attenuation of 0.5 dB (one way)
Cable attenuation 2.5 dB (one way), return loss considered of being better than VSWR 1.05
VSWR, Cable Connector (1.1)
Kathrein T. Wulff 08/2002
VSWR CalculationExample of an advanced site calculationVSWR, Antenna (1.5) + VSWR, Cable Connector (1.1)Calculate the total VSWR at the end of the cable to the antenna:VSWR 1.5 + VSWR 1.1 = VSWR total 1,65VSWR 1.65 = 12.2 dB return loss
Jumper CableAdd the cable attenuation twice, since the signal has to pass the cable up to theantenna and down to the connector. Add this attenuation to the upper return loss:12.2 dB + 1 dB = 13.2 dB
Feeder CableAdd the cable attenuation twice13.2 dB + 5 dB = 18.2 dB
Re-calculate the new VSWR value out of the new return loss:18.2 dB = VSWR 1.28
VSWR measurement at the input connector - WORST CASE CALCULATION !Add connector VSWR to VSWR of antenna-cable-assembly:VSWR site = VSWR 1.28 + VSWR 1.1 = 1.45 = 14.8 dB return loss
Kathrein T. Wulff 08/2002
VSWR Calculation
Conclusion
A rule of thumb site calculation is being considered as
an appropriated step to get an idea about the
expected VSWR performance!
Run this calculation prior to a site measurement.
Kathrein T. Wulff 08/2002
VSWR Calculation
VSWR 1.5 versus VSWR 1.3
VSWR 1.5 1.4 1.3Missmatch loss (dB) 0.18 0.13 0.08
A difference of only 0.1 dB results comparing a VSWR of 1.5 versus a VSWR of 1.3
- 0.1 dB equals a increased loss of 2%
This value is insignificant small and marginal!
VSWR Calculation
Rule of Thumb Calculation
Advanced Calculation
Conclusion
Site Calculations
Improper Calculation
Adding different VSWR values
Kathrein T. Wulff 08/2002
VSWR Statement
Conclusion
VSWR of better 1.5 is required for- broadband antennas- antennas with adjustable electrical down tilt
All major antenna suppliers are focused on broadband IMT 2000/UMTS antennas
VSWR of 1.5 is the world wide standard
VSWR Calculation
Rule of Thumb Calculation
Advanced Calculation
Conclusion
Site Calculations
Improper Calculation
Adding different VSWR values