I just began working on a new project that involves reading RFID tags, especiall UHF RFID tags. After doing some research on the available solutions, I came across the Cottonwood reader board. (here's the wiki: http://linksprite.com/wiki/index.php5?title=Cottonwood:_UHF_Long_distance_RFID_reader_module)

The cottonwood reader board (uses external antenna)

I found the schematic for the board and was shocked to see that:

  1. The AS3992 costs $65 on digikey and seems to be older, and less available.
  2. The coupler, RCP890A05, is so old that I can only find it on aliexpress. And it costs $8 or so.

I have done a few PCB design projects in eagle in the past few years, so I think I can lay out a design, but I'm looking for pointers that would help me reduce my cost to $50 for the components on this board and strip it down to the bare minimum.

It looks like there is another chip on here that acts as a generic microcontroller. At this point I plan to use a different chip so I can use wifi/bluetooth with this device, so that part is basically eliminated.

So I guess this all boils down to, what I can switch out to reduce costs and make parts more available?

Cheers, David

  • 1
    \$\begingroup\$ The directional coupler looks like it could be any generic part. The analog-front-end (the AS3992) will probably be the hardest part to replace. Also, if you haven't done RF PCB layout before, I'd suggest reading all the app-notes you can find, there's a lot of caveats and constraints to be aware of. \$\endgroup\$ Nov 19, 2016 at 5:08

1 Answer 1


The only UHF RFID Reader IC makers I know of are AMS, EM Micro, NXP and Impinj. (AMS recently sold RFID assets to ST Micro)

To use any of these ICs, you have to design RF hardware and then invest in thousands of lines of code to configure the IC, read the tags and output the data.

AMS has done the best job of publishing reference design boards and code, which is exactly why you are seeing designs using their AS3992 IC.

I therefore conclude that it's unlikely that you will come up with a cheaper board in a reasonable amount of time.

In fact, I would recommend that you seriously consider at least starting with a good reference reader such as the Thingmagic readers and OEM modules. You will probably find an AS3992 IC inside!


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