Antenna matching network on ESP32-PICO-D4

Baoshi
Posts: 14
Joined: Sun Nov 22, 2015 3:30 am

Antenna matching network on ESP32-PICO-D4

Postby Baoshi » Tue Oct 17, 2017 2:40 pm

Hi,

In the ESP32-Pico-D4 datasheet, the reference schematic shows a matching network after antenna.
matching.png
matching.png (11.23 KiB) Viewed 189 times

But the values are all TBD.
I notice that on the many development boards made by Microwavemont the LNA_IN pin is directly connected to the PCB antenna.
Currently I have some "W3008C" https://www.digikey.com/product-detail/ ... ND/2543332 ceramic antenna (50ohm impedance). Can I also omit the matching network?

Thanks

Baoshi

Lucas.Hutchinson
Posts: 66
Joined: Tue Apr 26, 2016 5:10 am

Re: Antenna matching network on ESP32-PICO-D4

Postby Lucas.Hutchinson » Tue Oct 17, 2017 7:21 pm

Antenna matching is very dependant on your specific board and board design, hence the TBD values.

(edit: i realise this paragraph relates to the normal esp32 chip and not the pico-d4)
A 50ohm antenna is not a perfect match for what the ESP32 outputs, i belive is it something like 30+ j??.
However it is a relatively close match and to a 50ohm antenna would only experience about 0.6dB of insertion loss from the antenna mis-match.

If you want the best range possible, you would need to manually tune the antenna using either a spectrum analyser or a vector network analyser to ensure a perfect antenna match.
Last edited by Lucas.Hutchinson on Wed Oct 18, 2017 9:19 pm, edited 1 time in total.

WiFive
Posts: 1164
Joined: Tue Dec 01, 2015 7:35 am

Re: Antenna matching network on ESP32-PICO-D4

Postby WiFive » Tue Oct 17, 2017 10:29 pm

ESP32-PICO-D4 integrates all peripheral components seamlessly, including a crystal oscillator, flash, filter capacitors and RF matching links in one single package.


So it should be 50ohm matched already. Additional external matching or filtering elements may or may not be needed depending on antenna and layout. Sometimes you will see a 0ohm resistor used and the caps unpopulated but they are designed in to give the option for tuning.

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