ESP8266 Community Forum

i have designed a circuit using esp8266 01 module. In my final design i just want to use the esp8266ex chip along with the antenna excluding the flash and crystal from the module. I need help for the antenna design. what should be done for impedance matching of the antenna? please help.

Thanks in advance.

I just went through this for the design of my Arachnio (obligatory plug: now on Kickstarter https://www.kickstarter.com/projects/lo ... o/arachnio), and it worked out pretty well.

This is extra-easy for the ESP8266, since the antenna pin is a single-ended 50 ohm line. Therefore, the only matching network you really need is a single blocking cap of 5.6 pF. Make sure it's an RF capacitor with a self-resonant frequency well above 2.4 GHz. It will cost more than you are used to paying for a chip capacitor, but not too much.

The cheapest way to do the antenna (at least on a per board basis -- this is more work) is to slavishly copy someone else's printed antenna design. This is what I did for the Arachnio. If you have a microscope set up for measuring or a set of gerbers, you could directly copy the antenna from an existing ESP module. They mostly seem to be pretty good. Another possibility is copying one of the designs from another company's app note. Both TI and Freescale have published excellent app notes discussing different antenna designs. If you use them, treat all dimensions as critical, especially ground spacing and PCB thickness/material and copper weight. Those things really do matter to get the antenna performance the designer intended.

If you are willing to spend more money per board in exchange for doing less work, there are a variety of chip antennas available. My favorite by far is this one from Molex (http://www.digikey.com/product-detail/e ... ND/2683663), because it's got relatively good performance and is admirably unfussy about where it's installed, so it gives you lots of design flexibility. It also costs almost as much as the ESP8266 itself does, so you may not want it. Regular chip antennas tend to be a little bit fussy about how they are installed. Read the manufacturer's data sheets and app notes and unless you are experienced with antenna design, follow them without question.

Thank you for the detailed guidance. It would be very helpful if u guide me to the gerber files of the esp8266 and also selection criteria for choosing the pcb material.

The gerbers will be released when the first boards come back from production. In the mean time, check out the following app note from TI: http://www.ti.com/lit/an/swra161b/swra161b.pdf. It goes into a lot more depth than I could in a comment and it has links to the specific reference designs. As for material selection, follow the instructions in the design you are using.