ESP32 Forum

Hello Mr. and Mrs.,

i don't think Your on-chip antenna-design ist best. The antenna should be a straight line and not criss-cross.

Best regards,

Sven Bieg

Two orthogonal lines okay, but not in the opposite direction.

The antenna design we use on our modules is a meandered printed inverted-F antenna. You seem to be describing either a dipole or a non-meandered inverted F. Can I ask why you believe that to be 'better'?

I don't think electro-magnetic waves can be captured better this way. I would prefer this way:

The longest antenna in the world!

Do you have anything to substantiate that opinion with? Because as far as I can see, an angled antenna like this is not a common design. This means either it is not common because it doesn't function well so no one uses this, or because it works pretty well but you are the very first person to come up with this idea. Given the simplicity of the design and the fact that antenna design by now is a pretty well-established field, I hope you don't mind me for heuristically assuming the former is more likely.

If You open any smartphone and take a look inside, You can see that this is a very common design. I'm wondering who came up with the criss-cross idea. It is simple mathmatics that opposite lines eliminate the signal.

I don't have the tools to open my phone here, so do you perhaps have an image of an actual design like that? I can imagine a non-meandered inverted-F design for higher frequencies or where there is room to expand the antenna to a quarter-lambda, but the 90 degree angle seems very suspect to me, especially if it's not at the feeding point.

And if I learned anything is that yer normal high-school math and physics don't work on antennas, not without taking everything there is about high-frequency waves into account. For instance, not sure if you noticed, but the antenna we have is actually shorted to ground, so logically, there is no ESP module that can actually send/receive WiFi. (It's good that the modules/antennas themselves are unaware of this fact.)

I think a microstrip antenna is a good option. Microstrip antenna also called printed antenna is a recent invention which was designed to incorporate antenna and RF electronics seamlessly on a PCB on a silicon chip.

Sven, this inverted F antenna design is not new and is rather widely used. There are a couple benefits to using this type of antenna:

• It is a small antenna compared to many other designs, which is great for a PCB antenna and for creating small IoT devices.
• The antenna is nearly omnidirectional in 3D. Simple monopole/dipole antennas are omnidirectional in a plane (2D), but are less sensitive out of the plane. For networked devices in buildings, where routers or other connected devices can be above or below as well as to the side, this 3D omnidirectionality can be very useful.

I see one issue with your proposed L-shaped antenna: you are crossing many of the ESP32 pins on the right side, which will interfere with the RF performance. You would need to move the whole antenna up above the top side to avoid interference, which would increase the PCB footprint.

In any case, nearly all of the ESP32 boards come in variants with a connector for an external antenna instead of the PCB antenna, so you are free to use other antenna designs based on your particular needs and space availability.