Questions about CC2500 and other RF

I do not do `hard' rf much but the antenna is critical. Not only the size but also the right shape (if it is a PCB antenna), matching, etc (we discovered that even the kind of FR4 matters). Also the placement of the rf portion relative to the rest of the circuit is important (like placing a folded dipole over a ground plane will not work). It is fun ... unless you are on a deadline. The kind of signal you are transmitting and the `cleanliness' of the channel are perhaps even more important. So ... whiten, interleave, listen, and hop! I still have not managed to get 50m performance the datasheet claims with their eZ430-RF2500 kit (even the preloaded app that came with it only gave us about 30 ft). Good luck!

Hej Robert!

My suggestion would be to buy the CC2510 Mini kit (http://focus.ti.com/docs/toolsw/folders/print/cc2510dk-mini.html) and do some practical measurement. I know customers who bought this kit measured over 300m LOS range! The CC2510 have more or less exactly the same RF performance as the CC2500 but it also have an MCU (8051) integrated. So, for $75 you will get everything you need to do some testing/fast prototyping!

Robert Åkerblom-Andersson said:

Hi, I just wonder what range can I get if I embedded an CC2500 chip into one of our products? How critical is the antenna? How big does it have to be?

Then I also would like to ask some general questions about RF worldwide, is it 2.4 GHz that is one to go with if I want my product to work all over the world? Or how do companies usually solve this with different frequency ranges in the US and Europe and the rest of the world? Is it common to use different chip for different part of the world? (Example on TI ICs for a setup like this would be nice).

Our application does not need to send that much information, range has higher priority, but we also want to use a free band (is about home automation). Do you have any general tips? We are looking at the CC2500 + an cheep MCU like an MSP430F2013 e.g. (I have read a little about CC430 but they are not as cheep or available at the moment right?)

 

Sincerely

So, there are a lot of apps notes that help answer these questions:

Antenna Selection guide: http://focus.ti.com/general/docs/litabsmultiplefilelist.tsp?literatureNumber=swra161a

Synopsis is that the antenna wants to be 1/4 wavelength, and a whip one is best, can do PCB ones or chip ones, they are not as good, but smaller.  There are layouts for different antennas that you can get from TI for our parts.

Range measurements:

http://focus.ti.com/general/docs/litabsmultiplefilelist.tsp?literatureNumber=swra169a

Here the big thing here is data rate.  Lower the data rate the further the range.  Other things also affect range, but this is the biggie.

2.4GHz is pretty much universally free to use.  Sub 1GHz are different bands in different countries (433, 868, 915, 950 to name a few) and while they all offer more range (lower frequency = more range), you can not have a single solution for all these bands (matching networks at a minimum will not allow it).  If you look at the sub-1 GHz band, TI has offerings for both the 433/868/915 band (CC1101) and a chip for the 480/950 band (CC1100E), so for these bands you need multiple chips and multiple PCBs to best match.  Range is better, but regulations are more varied and time consuming to get a product verified okay for all the different markets.

Are you aware of the RF4CE home automation market that is coming out, a similar system to ZigBee but for remote controls and other home automation things.  This http://focus.ti.com/docs/solution/folders/print/518.html tells more about it and TI has a solution including the software (though since the standard is not set in stone yet, it might vary some).  Remember too the CC430 is sub-1 GHz, so that will be for the 433/868/915 bands only.

This is Chris Pinter with Pinter Electronics Consulting. I am an RF Engineer and will offer you some suggestions. If you need to get a hold of me directly please visit http://www.pinterec.ca/contacthtml.html

I was able to get a range of over 200 meters line of site using an evaluation kit.  It is critical to choose the right antenna and make sure the impedance matching of the balun is very good.   In addition if you like you can design a circuit using the CC2500 that will have a range greater than 3 Km.   However, you will need an low noise amplifier, Power amplifier and a reasonable antenna to do this.

The TI devices are made for 2.4GHz so that the device can remain small.  The antenna can be a inch long and have good radiation.  If you want better range then you need to lower the frequency.

Since you have some requirements that are specific to your application it might be worthwhile to develop a specification document that outlines the best solution to meet you application.  If you like I can help you define the technical specification and provide you a design concept to meet your requirements.

If you are interested and require more information please do not hesitate to contact me directly.   http://www.pinterec.ca/contacthtml.html

Chris Pinter

http://www.pinterec.ca