jeremybirch
Posts: 3
Joined: Tue Jun 05, 2012 2:36 pm

HAT blocks or weakens WIFI

Mon Mar 25, 2019 2:45 pm

I am in the process of developing a HAT design, and my first prototype works OK on a Pi 3B+ but with one major drawback - it seems to block much of the WIFI signal from the board so that it is only visible to other devices from a narrow range of directions.

I suspect this is because my board has quite solid ground planes and of course due to the HAT spec is lying directly over the Pi antenna but 11mm or so away.

Does anyone know how large an aperture I need to make in my HAT design's power planes to allow for a good WIFI signal?

alphanumeric
Posts: 1693
Joined: Tue Jan 19, 2016 2:17 pm
Location: Sydney, Nova Scotia, Canada

Re: HAT blocks or weakens WIFI

Thu Apr 04, 2019 10:52 pm

I can't answer your question directly but may have an alternate solution? Maybe putting more distance between your Hat and the Pi may help?
Maybe a booster header, https://shop.pimoroni.com/products/booster-header
and taller standoffs https://www.adafruit.com/product/2337
Or a stacking header, https://www.adafruit.com/product/1979 and tall standoffs?

hippy
Posts: 4884
Joined: Fri Sep 09, 2011 10:34 pm
Location: UK

Re: HAT blocks or weakens WIFI

Fri Apr 05, 2019 12:40 am

Maybe perforate the ground plane near the antenna, add some holes or slots the radio waves can 'leak through' ?

You can probably prototype and experiment with an un-etched copper clad board tied to 0V.

mattmiller
Posts: 2058
Joined: Thu Feb 05, 2015 11:25 pm

Re: HAT blocks or weakens WIFI

Fri Apr 05, 2019 8:21 am

JAAMOI Where is the wi-fi antenna on a Pi3B+ ?

alphanumeric
Posts: 1693
Joined: Tue Jan 19, 2016 2:17 pm
Location: Sydney, Nova Scotia, Canada

Re: HAT blocks or weakens WIFI

Fri Apr 05, 2019 8:30 am

mattmiller wrote:
Fri Apr 05, 2019 8:21 am
JAAMOI Where is the wi-fi antenna on a Pi3B+ ?
Its that triangle shaped indentation on edge of the board right next to the WIFI chip.

mattmiller
Posts: 2058
Joined: Thu Feb 05, 2015 11:25 pm

Re: HAT blocks or weakens WIFI

Fri Apr 05, 2019 8:48 am

#LOL
I looked for a triangle shape but couldn't find it it (eyesight genuinely not good any more) - what big thing is it near ? :)

hippy
Posts: 4884
Joined: Fri Sep 09, 2011 10:34 pm
Location: UK

Re: HAT blocks or weakens WIFI

Fri Apr 05, 2019 9:05 am

To the left of the metal-cased WiFi module, between the mounting hole and connector. The "Made in the UK" silk-screening passes over it -

https://www.jeffgeerling.com/sites/jeff ... d-logo.jpg

mattmiller
Posts: 2058
Joined: Thu Feb 05, 2015 11:25 pm

Re: HAT blocks or weakens WIFI

Fri Apr 05, 2019 9:25 am

Got it now ta - didn't know the metal thing with raspberry logo was the WiFi chip!

hippy
Posts: 4884
Joined: Fri Sep 09, 2011 10:34 pm
Location: UK

Re: HAT blocks or weakens WIFI

Fri Apr 05, 2019 11:15 am

There's a rather nice x-ray of the 3B+ WiFi module giving an inkling of what's under the hood and showing the antenna off to its left here -

https://blog.pimoroni.com/content/image ... ll-6-1.jpg

I'm sure there was a photo of the WiFi module with its casing removed but can't currently find that.

As I understand it, turning the WiFi into a module meant it could more easily be used on other Pi variants such as the 3A+, can be certified without having to go through a more involved, more costly, testing process.

fruitoftheloom
Posts: 19363
Joined: Tue Mar 25, 2014 12:40 pm
Location: Delightful Dorset

Re: HAT blocks or weakens WIFI

Fri Apr 05, 2019 11:37 am

hippy wrote:
Fri Apr 05, 2019 11:15 am
There's a rather nice x-ray of the 3B+ WiFi module giving an inkling of what's under the hood and showing the antenna off to its left here -

https://blog.pimoroni.com/content/image ... ll-6-1.jpg

I'm sure there was a photo of the WiFi module with its casing removed but can't currently find that.

As I understand it, turning the WiFi into a module meant it could more easily be used on other Pi variants such as the 3A+, can be certified without having to go through a more involved, more costly, testing process.

This blog has good pictures / description:

https://www.google.com/amp/s/blog.pimor ... dware/amp/



https://www.raspberrypi.org/blog/raspbe ... le-now-35/

Dual-band wireless LAN and Bluetooth are provided by the Cypress CYW43455 “combo” chip, connected to a Proant PCB antenna similar to the one used on Raspberry Pi Zero W.
adieu

My other Computer is an Asus CS10 ChromeBit running Chrome Operating System.
HP Envy 4500 Wireless Printer supported by HPLIP software in Raspbian Stretch.

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