VSWR Calculator

Here's a simple VSWR calculator. Enter a value for VSWR (remember: VSWR should be a number larger than 1.0 or the results don't mean anything!).

Enter VSWR:

Reflection Coefficient

Reflected Power (%)

Reflected Power (dB)

Mismatch Loss (dB)

Where do these calculations come from? Well, start with the formula for VSWR:

vswr formula

If we invert this formula, we can calculate the reflection coefficient (, or the return loss, s11) from the VSWR:

reflection coefficient as a function of vswr

Now, this reflection coefficient is actually defined in terms of voltage. We really want to know how much power is being reflected. This will be proportional to the square of the voltage (V^2). Hence, the reflected power in percent will be:

reflected power percentage

We can convert reflected power to decibels simply:

reflected power dB, or return loss

Finally, the power is either reflected or delivered to the antenna. The amount delivered to the antenna is written as (), and is simply (1-^2). This is known as mismatch loss. This is the amount of power that is lost due to impedance mismatch, and we can calculate that fairly easily:

mismatch loss in dB

And that's all we need to know to go back and forth between VSWR, s11/return loss, and mismatch loss. I hope you've had as great of a time as I've had.

Full Explanation on VSWR: VSWR

Antenna Definitions

Home: Antenna-Theory.com (Home)

This VSWR calculator is copyrighted. Please don't reproduce it, unless you link back to the page and have permission. Copyright antenna-theory.com, 2009-2013.