LoRa/LoRaWAN tutorial 33: VSWR or SWR and Reflection Coefficient or S11

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This is part 33 of the LoRa/LoRaWAN tutorial.

In this video series different topics will be explained which will help you to understand LoRa/LoRaWAN.
It is recommended to watch each video sequentially as I may refer to certain LoRa/LoRaWAN topics explained earlier.

The parameters SWR and S11 are often used to judge the antenna performance.
In this tutorial I will explain what these two parameters are.

The Voltage Standing Wave Ratio (VSWR), pronounced “viswar”, often referred to as SWR is how much of the power offered to the antenna is reflected back.
It is the ratio of power offered to power reflected.
This is the same as how well the antenna impedance (Zload) is matched to the source (Zsource) it is connected to.

The reflection coefficient (Γ) is also known as S11.
The reflection coefficient values: between -1 and 1
The VSWR values, greater or equal than 1.
A VSWR = 1, no power is reflected (ideal situation), that is what we want.

Return loss is how much of the input power is reflected back and it is measured in dB.
If a return loss is 20 dB, it means -20 dB.

If RL = 0 dB: It means 0 dB, the ratio is 1, 100% of Pin is reflected back.
If RL = 3 dB: It means -3 dB, the ratio is 0.5, 50% of Pin is reflected back.
If RL = 10 dB: It means -10 dB, the ratio is 0.1, 10% of Pin is reflected back.
If RL = 20 dB: It means -20 dB, the ratio is 0.01, 1% of Pin is reflected back.
If RL = 30 dB: It means -30 dB, the ratio is 0.001, 0.1% of Pin is reflected back.
A higher return loss value results in a better antenna performance.

In an ideal situation when no power is reflected back, (ZL = ZS) the VSWR = 1.0 or as commonly expressed as a ratio of 1:1.
The higher the impedance mismatch, the higher the VSWR value.
If Zsource is smaller than Zload than power is reflected back, for example VSWR = 1.4 or 1.4:1.

The logged data can be found at:
https://www.mobilefish.com/download/l...

In total there were 4 nearby gateways which were able to receive my transmitted sensor data, see:
https://drive.google.com/open?id=1G-3...

Check out all my other LoRa/LoRaWAN tutorial videos:
   • LoRa/LoRaWAN tutorials  

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The presentation used in this video tutorial can be found at:
https://www.mobilefish.com/developer/...

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