Multiplexing Multiple RFID Antennas

Thanks Josh!

That's a huge help, much appreciated. As a follow up, I was looking at the PE42440 (http://www.psemi.com/pdf/datasheets/pe42440ds.pdf) and noticed that there's also an evaluation kit that uses coaxial cables. Would I be able to use the basic PE42440 alone to multiplex between coax antennas? The PE42440 is around ~$3.00 where as the evaluation kit is over $100, so I want to make sure I order the right one :P

Parker -

i used the 42440 and the 4257 eval boards for proof of concept myself - then built the actual boards. (i cascaded them even in the final example, to support 16 antennas from one reader)

just in case you use Eagle - i made the footprints for these parts, too. just let me know.

Hey Josh,

Thanks for the quick reply! And the Eagle files woud be a huge 

Thanks again,

Parker

Parker -

the PE42440 package is in the texas.lbr zip file (attached)

8080.texas.zip

the PE4257 is in the RFID Automotive library zip file.

1030.RFID_Automotive.zip

Hi, Josh,

Thanks for this very useful reference design. My question is, to build a 1:16 MUX, what would be the benefit of your design over cascading 5 SP4T like PE42440/PE42641?

I am trying to build a 1:100+ multiplexer, when I went through your design, I realized if I go with your design, like cascade 32 antenna board, I will not be able to find any microcontroller that has enough GPIOs.

Please forgive my ignorance, I am a total newbie.

Thanks,

ZLi

ZLi,

I couldnt get hold of any Peregrin switches, but managed get some Skyworks devices. Skyworks also seem to offer higher count switches.

I'm using multiple SKY13412-487LF (SP12T) switches to switch to 20 coils, and they seem to work fine. Each switch takes 4 IO to switch, but you could be clever with your switching to get your required pin count right down (to 8 pins) - use 10 switches to switch your coils (all with identical control IO connections) and an 11th switch switches RF to those 10.

Just a thought...

Carefully check out the app notes from Skyworks and Psemi -- some of their parts require blocking caps (if dc is present) and discharge resistors.

BR,

Eric Hooker

RF Consultant