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small PCB request for an open source project - RF Cafe Forums

Because of the high maintenance needed to monitor and filter spammers from the RF Cafe Forums, I decided that it would be best to just archive the pages to make all the good information posted in the past available for review. It is unfortunate that the scumbags of the world ruin an otherwise useful venue for people wanting to exchanged useful ideas and views. It seems that the more formal social media like Facebook pretty much dominate this kind of venue anymore anyway, so if you would like to post something on RF Cafe's Facebook page, please do.

Below are all of the forum threads, including all the responses to the original posts.


ZigDCC
Post subject: small PCB request for an open source project
Unread postPosted: Thu Jun 02, 2005 6:27 am

Hello folks,

May one of you develop a small 2x3cm PCB design for an RF headend including RF chip itself and optionnal space for SMT ceramic antenna?




Here is an idea of what this project would need to start using RF:

Image


From the middle to the left you can see Chipcon's cc2420, an IEEE 802.15.4 CoS working in the 2.4GHz ISM band.

On the bottom of this design (outside of this PCB) an antenna can be wired.

On the right side is a microprocessor and its cristal. That one is not needed anymore.


The new PCB must be designed as module which can be soldered on a motherboard which will be equipped with its own processor (Atmel, Microchip or what ever else is needed behind the head end).

The new PCB should also provide options to either SMT ceramic antenna onboard or for external (in house) antenna.


The cc2420 documentation is here:
http://www.chipcon.com/files/CC2420_Data_Sheet_1_2.pdf

With something like 6x8cm its reference design is a way too big to fit in small embedded applications and is also a way too expensive ($540 in Chipcon's webshop).

The cc2420 can be found for $4 and an SMT antenna costs not much more.

Objectives would be to meet $20 - maybe much less - for assembled cc2420 RF headend.



One of the issues I see (for costs) is that Chipcon's ref. design is based on a quad layer PCB.

I would expect a more standard dual layer PCB. Can this be acheived?



The chip itself features up to 100m RF range.

The project requirements will be to set up connexions from 4cm - only - to some 10th of meters.

From 4cm - only - to some 5 to 10 meters will be welcome if there are issues with huger ranges.



I could make several attempts by my own with Cadsoft's Eagle PCB design tool but this will probably not be the best way for RF and power efficiency.

Any volunter to take this over or does such a headend already exist and I missed it?


Best regards


Top


ZigDCC
Post subject:
Unread postPosted: Thu Jun 02, 2005 6:40 am

Here is a closest view of the chip on its ref. design:

Image


Top


Guest
Post subject:
Unread postPosted: Thu Jun 02, 2005 8:14 am

How much$$$$$$


Top


ZigDCC
Post subject:
Unread postPosted: Thu Jun 02, 2005 8:36 am

I have currently none, my last are gone in a cheap AVR JTAG programmer :)


What should I think from this:

http://www.egr.msu.edu/classes/ece480/g ... ctures.htm


Does it mean mimics of the ref design provide acceptable results?

Image


Regards


Top


ZigDCC
Post subject:
Unread postPosted: Thu Jun 02, 2005 10:41 am

I can add following regarding $$$

All ZigDCC related materials including the hardware designs will be made available under GNU GPL license.


for more informations see project aim at Sourceforge:
https://sourceforge.net/docman/display_doc.php?docid=28698&group_id=140277

Regards[/i]


Top


ZigDCC
Post subject:
Unread postPosted: Thu Jun 02, 2005 1:22 pm

I will leave that cc2420 aside because prototyping is too expensive due to quad layer PCB.

cc2500 is much more interesting as its ref design is only 2 layer PCB based. cc2500 differs also in the way it doesn't provide hardware encryption. A later cc2520 may feature this.



So the question is still open.

May one just mimic a ref. design and acheive honorous performances?

Regards



cc2500 specs can be found here:

http://www.chipcon.com/index.cfm?kat_id ... dok_id=183


PCB design is much more simple as shown here, on page 2:

http://www.chipcon.com/files/CC2500_221204_LoRes.pdf


Top


ZigDCC
Post subject:
Unread postPosted: Fri Jun 03, 2005 9:54 am

ZigDCC wrote:
So the question is still open.

May one just mimic a ref. design and acheive honorous performances?



not sure... I'd like to use standard 1.6mm FR4.

http://ieeexplore.ieee.org/iel4/5437/14 ... ber=667012

http://www.rogerscorporation.com/mwu/techtip4.htm



But all and every RF blocks are built inside the cc2420 so how could the substrate interact with the chip internals? Are such chips designed to be used exclusively on quad layers RO4000 substrates?


The loss throught strips to the antenna seems acceptable on RF4 knowing a ceramic chip antenna could be placed some 1/3 inch away from the RF chip itself:

Image



So why would one use expensive quad layer RO4000 substrate where FR4 may approx do the job?

What is approx, will it be close or less than 1dB or should several 10dB loss be more resonnable expectations?

Some WUSB components are qualified to work on standard FR4:
http://www.fractus.com/2-4.htm


Why should one use quad layer RO4000 where two layers FR4 may do the job?



The components and layout between the chip and the antenna may be an issue but everything can be wired really close and even unmatched according to chipcon's datasheet:

Quote:
The antenna should be connected as close as possible to the IC. If the antenna is located away from the RF pins the antenna should be matched to the feeding transmission line (50 ?).





I think I will give it a try in dual layer FR4 with a small ceramic chip antenna close to the RF CoS.

Dear Guest, have you an opinion about my chances? :wink:


Top


CK
Post subject:
Unread postPosted: Thu Jun 09, 2005 5:10 pm

Why Chipcon?
I've already seen early designs of this size on .8mm board material with F antenna on double sided FR4 using the Freescale MC13192 chip and 9S08 family processor with estimated costs lower than what you want.


Top


ck
Post subject: zigbee
Unread postPosted: Sat Jun 25, 2005 3:11 pm

CK wrote:
Why Chipcon?
I've already seen early designs of this size on .8mm board material with F antenna on double sided FR4 using the Freescale MC13192 chip and 9S08 family processor with estimated costs lower than what you want.

have you experience on zigbee?


Top


ZigDCC
Post subject:
Unread postPosted: Sat Jun 25, 2005 3:23 pm

ZigDCC wrote:
ZigDCC wrote:
So the question is still open.

HAVE YOU EXPERIENCE ON ZIGBEE?


May one just mimic a ref. design and acheive honorous performances?



not sure... I'd like to use standard 1.6mm FR4.

http://ieeexplore.ieee.org/iel4/5437/14 ... ber=667012

http://www.rogerscorporation.com/mwu/techtip4.htm



But all and every RF blocks are built inside the cc2420 so how could the substrate interact with the chip internals? Are such chips designed to be used exclusively on quad layers RO4000 substrates?


The loss throught strips to the antenna seems acceptable on RF4 knowing a ceramic chip antenna could be placed some 1/3 inch away from the RF chip itself:

Image



So why would one use expensive quad layer RO4000 substrate where FR4 may approx do the job?

What is approx, will it be close or less than 1dB or should several 10dB loss be more resonnable expectations?

Some WUSB components are qualified to work on standard FR4:
http://www.fractus.com/2-4.htm


Why should one use quad layer RO4000 where two layers FR4 may do the job?



The components and layout between the chip and the antenna may be an issue but everything can be wired really close and even unmatched according to chipcon's datasheet:

Quote:
The antenna should be connected as close as possible to the IC. If the antenna is located away from the RF pins the antenna should be matched to the feeding transmission line (50 ?).





I think I will give it a try in dual layer FR4 with a small ceramic chip antenna close to the RF CoS.

Dear Guest, have you an opinion about my chances? :wink:



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