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Okay, so I've got an UHFReader18 UHF RFID Reader from China, which can be seen here: http://www.aliexpress.com/store/product/Popular-800mm-UHF-RFID-Desktop-Reader-6B-6C/413622_598715812.html. The unit I have is not the exact model shown on the website, since my unit's antenna is extended outside of the main body. Here's a picture: enter image description here

The red bar is the antenna.

I've tested the device using the provided RFID cards, and using the provided software sample I was able to reliably read the RFID cards at a range of 30-40 cm. However, I'd like to know if it is possible in any way to increase the range of the RFID reading at one point or area, at the cost of minimising its coverage. The reader is intended to be used in a factory setting.

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  • \$\begingroup\$ I was just playing around with a UHF RFID unit for the first time today. It is a RFIDSecu RS-RI01 that was cheaper than that with a six meter range and the in-built antenna seems fairly directional. If buying a different unit was on the cards ping me in EE chat if you want to know anything more about it. \$\endgroup\$
    – PeterJ
    Commented Dec 17, 2014 at 6:51

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There's plenty of material (academic and otherwise) on this topic. My light reading of a bit of it suggested that it's pretty straightforward to used a phased array to read RFID tags, but you still need to energize them by delivering sufficient energy in the right band, and that's something that phased arrays just aren't very good at (they have good gain performance for reception, but have no benefit for transmission; you need different types of antenna for transmit gain).

A description of a commercial system that I read (sorry, I don't have a link) talked about using a phased array to read RFID cards at ~300m at a trade show in a big hall, but they had to have an energizer near the card. I've heard of energizers working at up to a couple of meters, but the inverse square law (2x distance, 1/4 power) is pretty hard to get around for power delivery - you need to transmit massive amounts of power in the right band to get any range out of your energizer.

In your context, part of your range problem is almost certainly that the reason you get only 30-40cm is that's as far as the RFID tag can be and still receive enough energy to operate, because the energizer in your reader just doesn't put out much power.

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  • \$\begingroup\$ 300m is waaaay bigger than my factory floor. I was actually aiming to get around 1m... \$\endgroup\$
    – Sodrohu
    Commented Dec 17, 2014 at 6:37
  • \$\begingroup\$ I wouldn't be surprised if your system there can pick up a tag at 1m, but what it can't do is power the tag at that range. Ramp up its output power by a factor of 10 and see what you get in the way of range. \$\endgroup\$
    – markt
    Commented Dec 17, 2014 at 6:50
  • \$\begingroup\$ I'm not sure yet how to do that; the output power is controlled by the device, and my end only sends commands to change its output to the max level. What about using some kind of parabolic antenna to somewhat focus the read in one direction? \$\endgroup\$
    – Sodrohu
    Commented Dec 17, 2014 at 8:05
  • \$\begingroup\$ I'm no RF guru, so my ability to help with the specifics is pretty limited. There are some people on here that most certainly can help there though. I'd suggest that a functional parabolic antenna in the UHF band is going to be pretty large though; look at the size of a high gain 2.4GHz dish and extrapolate... \$\endgroup\$
    – markt
    Commented Dec 17, 2014 at 8:49

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