•−•  ••−•    −•−•  •−  ••−•  •
RF Cafe Morse Code >Hear It<

Job Board

About RF Cafe™


>10,000 Unique Pages!

RF Cafe Software

RF Cascade Worbook
 RF Cascade Workbook 2005 - RF Cafe
Calculator Workbook
RF Workbench
Smith Chart™ for Visio
Smith Chart™ for Excel
RF & EE Symbols Word
RF Stencils for Visio

Your RF Cafe
Progenitor & Webmaster

Click here to read about RF CafeKirt Blattenberger

Carpe Diem!
(Seize the Day!)

5th MOB:
My USAF radar shop

Airplanes and Rockets:
My personal hobby website

Equine Kingdom:
My daughter Sally's horse riding website

  VSWR Mismatch Errors

VSWR Mismatch Errors - RF CafeBoth amplitude and phase errors are introduced when mismatched impedances are present at an electrical interface. When an ideal match is not encountered by the incident (forward) wave, part of it is coupled to the load and part is reflected back to the source. Upon arriving back at the source, part of the reflected wave is coupled back to the source and the rest is reflected back again to the load. The process iterates until the amplitude of the wave is attenuated to an insignificant level due to the loss of the interface (cable, connector, waveguide, etc.). Each time a reverse and forward reflection occurs, the amplitude and phase of all the signal components traversing the path between the source and the load add vectorially. The result is ripple across the frequency band (since the VSWR of each interface typically varies with frequency), as well as a portion of the incident power being reflected back to the source. What begins as a pure sinewave can look like a real mess when viewed on an oscilloscope.


Amplitude Error

Note: Only enter values in the yellow cells or risk overwriting formulas!

εA = +20 * log (1 + |ΓA * ΓB|)  [dB]

        -20 * log (1 - |ΓA * ΓB|)  [dB]

Phase Error

εΦ = ±(180 / π) *| ΓA| * |ΓB|  [°]

Note: This formula has also been seen
            written as

εΦ= ±(180 / π) * sin-1 (|ΓA| * |ΓB|)  [°]

  but for small angles, the difference
  is negligible.

See a derivation of this equation as provided by Haris Tabakovic

Resultant MIN and MAX
Cascaded VSWR




SA = larger of the two VSWRs
SB = smaller of the two VSWRs


VSWRA = 2.5:1  -->  SA = 2.5
VSWRB = 2.0:1  -->  SB = 2.0
VSWRMAX = 2.5 * 2.0 = 5.0  = 5.0:1
VSWRMIN = 2.5 / 2.0 = 1.25  = 1.25:1

Here is a JavaScript calculator for VSWR / Return Loss / Reflection Coefficient / Mismatch Error / Improvement

SEARCH More Than 10,000 Pages Indexed on RF Cafe

Copyright 1996 - 2016
Webmaster:  Kirt Blattenberger, BSEE - KB3UON
Family Websites:  Airplanes and Rockets | Equine Kingdom

All trademarks, copyrights, patents, and other rights of ownership to images
and text used on the RF Cafe website are hereby acknowledged.