Typical size of a Creditcard version operating in the 850-930MHz
The ISOcard uses only 0.20 milliwatt of power and is simple
Extract from newsletter
Passive RFID transponder technology is driven by the need for RF
efficiency as wasted energy means larger readers, and less range; while
local regulations limit reader's power and hence system performance.
Trolley Scan have been world leaders in the past in developing extremely
low power RFID technology for very low cost RFID transponder systems, primarily
through their patented EcoTag(r) technology.
The measure of success used to monitor progress is a factor called "RF
sensitivity", that is how much RF energy has to land in the antenna
aperture of the transponder for it to operate reliably. For a typical dipole
based transponder at 915MHz the aperture is 134sq cms.
The reasoning for using RFsensitivity is
RFreader power is proportional to RF sensitivity/(Range*ramge)
Therefore improving the RFsensitivity by a factor of say 10 means the range
of the system will be 3.15 times more OR the reader power can be reduced
by a factor of 10 meaning smaller readers and longer battery life.
As as benchmark a 5volt logic circuit attached to dipole antenna on a transponder
would need 55 milliwatts to be collected in its antenna aperture to operate.
A perceived disadvantage of UHF RFID by some potential users has been the
length of the antenna. Typically the length is 160mm at 915MHz (slightly
longer for 869MHz for the EU) but this is needed in order to get high efficiency.
Taking a 160 mm long dipole and cutting off 40mm from each end would throw
away 97% of the efficiency of the system, that is the standard benchmark
transponder would need 1833mW to operate - obviously not a practical solution.
The wonders of EcoTag technology now come to the rescue for Trolley Scan
Using EcoTag patented technology, Trolley Scan have developed a simply
designed 80 mm long antenna system THAT OPERATES ON AN AMAZING 0.20mW (comma
two milliwatt) RF sensitivity, a 7000 times power improvement compared
to the shortened dipole, or 220 times improvement even compared to the
full length dipole.
The design allows the entire transponder to be packaged in an 80 by 33mm
area, and particularly into the standard ISOcard formats that are requested
by users particularly for access control cards or smart labels. (Credit
The new antenna design means that it is quite practical to read an ISOcard
sized transponder at 11 meters.
The Isocard version is suitable for attaching to metal and wood objects with minimal performance reduction
(PS Despite offering 11 meter range the sensitivity is so low that the new
EcoTag ISOcard transponder operates 1000 times below the power levels recommended
in the RF health guidelines).