RF Wireless Application

Hi, These RF ID tags are often SAW resonator, passive parts. You send a RF that is near to their tunning frequency then you get a reflected or resonant component back with signature. It requires RF source and RF analyzer instrument to get signature. RF ID is simply life a sticker with very tuny SAW resonator crystal (often made of Quartz) is pasted on to box or injected into (animals). You can buy these tags and also instrument. Why to rediscover the wheel once again?

Your idea sounds very similiar to existing "active" RFID designs which use quiescent power the same way described. Active RFID systems offer greater distances between transceivers (up to 30ft currently and still expanding that proximity). The tank circuit you refer to equtes to a type of SAW resonator, and is designed in some RF discrimminating circuits for RFID at an extra cost. It's possible to false trigger low cost RFID devices, however, like ethernet technologies (statistical collision data acknowledgement), the unique ID differentiates the transponder from all others and assures validity of the data received.

I am more interested in the technology that spawned RFID, namely RF-EAS. These are 'dumb' tags and labels that simply reflect an 8.2 MHz signal between antennas, or near transceiver antennas. The challenge is to come up with a design that is cost effective enough to be applied to individual, inexpensive items for security only. The current designs generally cost US$.06 per reusable tag, and US$.008 per disposable label to manufacture. There will obviously be an increase in cost, but if one can be designed that improves upon the current model significantly enough, a portion of the increased cost can be justified. My understanding of most RFID tags is that they are SIGNIFICANTLY higher in cost, and ultimately do much more than is needed in this application. Do any of you know anything about ulta capacitors? www.maxwell.com Perhaps these could improve detection distances in the re-usable type of EAS tags? Thanks for your input.

I used to work for a company that does the 8.2 MHz EAS. "Nature is a Mutha!" We are between a rock and a hard place. Since these are passive tags, we are limited by fundamental physics. The FCC only allows a certain amount of interrogator field strength, and thermal / environmental noise limits the detection threshold. What is needed is a HOT tag. We found that the return signature is proportional to area squared. Thus, increasing area helps quite a bit, but no one likes a big tag, especially for materials cost reasons. The Q of the resonance has a big effect. The capacitor is about as good as it gets using the typical poly propolene dielectric and is way better than the Q of the inductance. The conductor part of the tag is the limitation. Aluminum is used for the inductance as its conductivity for the price is the best trade off. Copper helps a bit, but its too expensive. What we really need is room temperature super conductors. This would revolutionize the whole thing, not to mention a whole host of other more important things. We d been doing tags for decades and theyre about as good as they can ever be. As for going active, standby battery power / life is a big insurmountable problem, cost being paramount. Best wishes with your search. We ve been there and done that!

Al, whom did you used to work for? I'm very interested.

You can email me if you like.

Kagansentry@aol.com

Thank you for your input Al. I'm curious, could an ultra-capacitor be used to boost the Q, or return signature. Forgive me if my terminology is off. I am not an engineer and not literate in the technology. Anyway, my understanding is that by changing the Capacitance in the circuit, you would end up with a different resonant frequency, unless, you altered impedance accordingly. But could a separate ultra capacitor be used somehow in or attached to the existing circuit to improve or boost the return signature? In understand, that like a battery, there would be added cost. Perhaps the improvement in performance for this type of system would be enough to offset that cost marketwise. Your thoughts?