ESP32 Forum

I'm currently in the making of a small control module for my WiRGBulb32 (not sure about this name yet though ) smart-light bulb project, which will be an open source project currently in development phase (will be shared in Showcase section next month when functioning prototype is ready).

I'm planning to use the PICO-D4 as the brain, with the same antenna as on the PICO-KIT (Proant 440).
I have trouble figuring out the ground plane and layer arrangement from looking at the PICO-KIT pictures.
I'm not an antenna expert, but I know that ground plane arrangement for the antenna is critical, and I want to get it right.

The module will be very small (15x20mm) which will contain just the antenna, matching circuit, and a PICO-D4. It will be mounted perpendicular at the center of the LED carrier.

I would be very grateful if you guys could provide some ideas, drawings, snapshots, of how I should design it, I that I can make sure that at least this part of my deisgn is good ... and to not screw up the Wifi performance, which is the essential part of this project.

Thanks in Advance.
Vader [BEN]

I thought you were using a chip antenna. Check the datasheet and app notes https://www.digikey.com/product-detail/ ... ND/4895684

I'm so glad that you asked this question. I've been looking for a solution like this and now I have one. Thanks Vader_Mester!

WiFive wrote:I thought you were using a chip antenna. Check the datasheet and app notes https://www.digikey.com/product-detail/ ... ND/4895684

Already did it from A to Z like 10 times this is the reason i am here.
I also seen through several others app notes as well like some from molex.

But antenna design is not exact. The presence of an IC and narrow ground plane have effects many things.
Espressif made some test models and I'm sure they found that out the hard way with great result

... or I just make some test models and hope for the best

If you haven't already, have a look at the ESP32-PICO-KIT, schematics that I just stumbled on myself: https://dl.espressif.com/dl/schematics/ ... ematic.pdf

It actually uses the Proant 440.

http://esp-idf.readthedocs.io/en/latest ... ico-kit-v4

Yeah, this was the idea. I studied it a lot, and I wanted to design according to this, because it is given, but now I realized, I have much much worse space requirements than before...
Additionally the stuff will be inside a smart bulb, and since it's not a low profile antenna, I'm worried it's gonna cause incorrect reflections.

I sort-of dumped the idea, and want to use a chip antenna instead...cause the design is given and it's... cheap so maybe I'll make a prototype, just to get everything else right, and then I correct the RF section later.

Still... I have to admit, that antenna design sux, and I literaly read half the internet for proper info, even though I'm an electrical engineering student, and this knowledge is fresh

Vader [BEN]

But doesn't a chip antenna suffer the same limitations?

It depends... A chip antenna in profile is smaller, but it needs to have a proper ground plane. But very sensitive to GND plane design placement (price of beign small)

Also the bandwidths are rather small, so... needs a lot of research.

It has pros though with the PICO, like no need for matching cirtuit, just a properly sized 50ohm feed line (which is difficult to do with OSH-park for example, since to achieve a good 50ohm feed line, you need 0.7mm wide trace with 0.1mm GND plane gap, but OSHpark offers 0.157mm for 2 layer and 0.127mm for 4 layer.

Below you see some mechanical studies on the subject.
White arc on the picture supposed to be the LED bulb lighshade (the first prototype has this type), which is the maximum mechanical constraint, but still wanna aviod too big modules, to not disturbe the light coming from the bulb.
1st Prototype will be OSHpark (with OSHpark's purple solder resist, but almost full PCB silk screen, to make it white).
Next prototype will be from Seeedstudio with White solder resist.

From most of these deisgns, all of them are almost flat, except for the Proant, where the antenna would protrude from the modules surface 3-4 mm, probably causing some incorrection in the light beam.

PCB will also has (on the PICO side and on the back side) a 3.3V LDO, some caps, and 2 transistors with resistors for level shifting to 5V. Will be soldered to the LED-board of the buld, using castellated edge pads (like on the ESP modules)