Help to identify small pcb trace wifi antenna

[Nightreaver]

I been trying to create a small pcb with an esp and expressLRS, for fun and practice.
And upon researching and creating my own pcb I'm mainly stuck at the antenna part.

I just found that there are similar products around using some interesting concepts.
Of course I know the "big" pcb trace antennas on all esp packages, but this trace antenna seem to be very small in comparison, I think its only around 5mm*3mm and still being for wifi.

I did some reasearch but could not found a similar design anywhere.
Maybe one of you guys can help to identify the design (hopefully not patented) so it can be replicated.

Original Product: GEPRC ELRS Nano SE Receiver (2.4HGhz)
As product size is only 12*10mm, the wifi antenna must be very small and different from regular esp pcb antennas
(I am not talking about the "SMD antenna", I really mean the pcb trace one)

This wifi antenna is mainly used for the initial setup/configuration/OTA, so no long ranges or big throughput required.

Cheers

[uer166]

It's an off-the-shelf SMD helical antenna for 2.4GHz, nothing weird. Plenty like this on DigiKey, but also it's not the smallest, this is relatively big compared to ceramic antennas, however this should have better efficiency (usually efficiency is inversely proportional to size).

[Nightreaver]

I dont mean that antenna, this is the one for eLRS signal, I mean the antenna in the picture, marked as "Wifi Antenna".

I have attached another picturse with a similar antenna ( I guess). As they are on the PCB side with the ESP, I suspect them to be 2.4Ghz

[uer166]

Ah, that looks like an exceptionally bad meander PCB antenna. It will probably work if you're right next to the AP, but considering how close it is to the GND plane (and due to lack of matching components), it's probably like 1% efficient and not tuned to the correct impedance.

[uer166]

You'd have much better performance even with a relatively poor chip antenna.

[Miek]

It's pretty common on these ELRS boards for the designers to not care too much about the wifi antenna and prioritise saving space instead. As you say, it doesn't need long range or throughput, so they place something down that resembles an antenna and works well enough, but isn't anywhere near optimal.

[Randy222]

The goal is to make a resonant antenna for 2.4GHz?
Stripline or co-planar feed-pad is pretty simple to do direct on PCB.
Or is the question more about sourcing an antenna that you can just solder to the board?

[Nightreaver]

I would like to clone/extend specific existing boards for special usecase where I need small board size but not so long range (speaking of 2 3 meters).
As my board is already quite cramped Im looking for alternatives that dont need a lot of clearance, and it seemed that antenna doesnt need it, but obviously it does as well, they just dont care

[Randy222]

This wifi antenna is mainly used for the initial setup/configuration/OTA, so no long ranges or big throughput required.

Cheers

I think you need to start by defining the actual distance you need this to work at.

If your "programmer" Tx is like 3ft away, then you might not need an antenna at all. Or in crude way, just a 50ohm stripline about 1.5" long should suffice.

Or skip pcb style antenna, just install a discrete off-the-shelf smd antenna, done.

https://www.antennacompany.com/product/ac10300-wifi-6-6e-7-bluetooth-embedded-surface-mount-ceramic-chip-antenna/

[tszaboo]

Ah, that looks like an exceptionally bad meander PCB antenna. It will probably work if you're right next to the AP, but considering how close it is to the GND plane (and due to lack of matching components), it's probably like 1% efficient and not tuned to the correct impedance.

Not only that, but the ESP8266 and ESP32 chips with default TX power are quite above the legal limits for Europe. With that much power, even a paperclip would work as an "OK antenna".

[Nightreaver]

I have created a separate topic for the implementation here https://www.eevblog.com/forum/rf-microwave/how-to-implement-antennaantenna-tuning-(is-it-required)/