So, I'm struggling to understand what the S-parameter is in real-life terms; I mean, what does the S-parameter tell us about an antenna?
I have designed a microstrip Wi-Fi antenna that should work at around 2.4 GHz
I have simulated it and as the image below shows, the S-parameter seems correct to me with its down peaking at 2.4 GHz
My problem is, practically speaking, what shows me the S-parameter?
I know that the parameter describes how voltages or currents behave in bi or quadripole but I can't understand how to mirror this theoretical description in my specific example with an antenna working on a certain frequency
Best Answer
S-parameters are a way of expressing things with general waves instead of voltages and currents. It describes how much the waves are reflected or transmitted from/through a device.
With a device like an antenna, there‘s not only 1 but 4 S-parameters. The first one S_11 is also known as the the reflection coefficient.
If an antenna is tuned and matched, it is obvious that S_11 should be as small as possible at the operating frequency. (No wave should be reflected when feeding the antenna)
Maybe you don‘t want your antenna to be tuned to 2.4GHz, but to 2.44GHz, because with most radios like ZigBee or Bluetooth, you want to tune the antenna to the center of the frequency band.