RFID-Radar^TM Frequently asked questions(FAQ)

What is the big deal with this technology?

To explain the problems associated with measuring range using RFID-radar technology one can consider a simile.

Imagine you are sitting on a chair at the edge of a large lake on a pitch black night, overcast with no stars. There are no visual references to use for range estimation. A boat somewhere out on the lake flashes a torch briefly and the person on the chair has to calculate the range of the boat from the chair to an accuracy of 1 meter. There are no other people on chairs on the lake that can also give information, just you on your chair, possibly with one eye closed. This highlights the technical challenges we have overcome using this invention.

Now imagine there are 50 boats out there scattered randomly, who all flash their lights briefly and are expecting their location to be identified.

Now imagine all the boats start moving and you have to track their individual paths while sitting on your chair.

How intensive is the computing problem for this invention?

An RFID-radar system tracking 50 targets that are moving can generate a lot of information. The load is most probably similar to that of AWAC aircraft flying above a battlefield. Each target in the zone has to have its own set of complex equations to describe its movement in isolation from all the other targets.

Despite this large amount of source information, the calculations are done in the reader and the reader can condense the information on each target to identity and coordinate details only so as not to overload the computer network.

What are the practical problems with measuring the distance a signal has travelled from a reader to a transponder

Radio waves travel at 300 000 km/sec. Due to there being many users of the radio spectrum trying to share a very limited spectrum, operating bandwidths for practical RFID systems are only tens of kiloHertz wide. This means measuring accuracies for time of travel of the order of 0.1 milliseconds(each tick of the clock). With this resolution for measuring the range of a tag by the time of travel of a signal results in an uncertainty in position measurement of 30 kilometers for each tick of the clock. RFID-radar has overcome this challenge and measures the range from a transponder to a reader.

Does RFID-radar use triangulation to measure range?

The RFID-radar has a single set of antennas mounted next to the radar processing box. From this single location, the radar measures the range to each target and computes the apparent arrival angles at this one antenna location. From this range and bearing information, the RFID-radar can determine the location of multiple targets in the zone. The RFID-radar does not use triangulation, which would require other remote antenna systems. Because of its single antenna set for reading location, RFID radar is suitable for mobile applications, like mounting on a fork lift truck, to identify goods in the vicinity of the fork lift truck.

Does RFID-radar use signal strength variation to measure range?

Signals travelling from a transponder to the reader would dissipate their energy in all directions radiating from the transponder, causing a variation of signal strength as one travels further from the transponder. However any signal hitting any hard object in any location around a transponder(even a floor or a wall), would also cause a radiation signal which would have similar characteristics and which would interfere with the original signal, either reducing or increasing its strength - commonly known as multipath. Multipath corrupts the characteristic of signal strength and reduces its ability to be an indicator of range, especially over long range. To overcome multipath and hear signals that are close, or far at the same time, RFID-radar can accept variations in signal strength of more than 100 000 times. RFID-radar does NOT use signal strength as an indicator of range.

Will RFID-radar work with different brands of transponders?

Initially RFID-radars are being produced to work with Trolleyponder, EcoTag and similar passive transponders.It will also work with certain active transponders to give greater operational range. Later other brands of transponders can be added to the lists of transponders that can be used with this new technology once the RFID-radar reader is adapted to read the other brands of transponders.

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