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Autocalibration of BiStatix® RFID Tag Read Range Test Disclosure Number: IPCOM000005602D
Original Publication Date: 2001-Oct-18
Included in the Prior Art Database: 2001-Oct-18
Document File: 4 page(s) / 157K

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James G. Quaderer: AUTHOR


Autocalibration of BiStatix® RFID Tag Read Range Test

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Autocalibration of BiStatix® RFID Tag Read Range Test

By James G. Quaderer

                    In order to maintain quality during the manufacture of RFID tags, it is necessary to have at least an attribute (pass/fail) test of outgoing product before it is shipped to the final customer.  Inductive RFID tags are almost entirely produced in electronics manufacturing facilities where RF test engineers are readily available.  Because of the use of standard coils, most inductive RFID tags are of a standard size and performance so that changes in the test are few, it is good enough to have an RF test engineer design the final outgoing test equipment and not have to change that equipment for possibly years at a time. 

Figure 1

                    Capacitively-coupled BiStatix® tags do not contain a coil; their printed conductive ink antennae can be of nearly any shape and size to suit a large variety of applications not possible with coil antennae.  These applications are implemented by the printer converters and will require frequent final read range test changes as new applications develop.  BiStatix® tags are produced by simply adhering a thin prefabricated interposer (RF transponder) to the printed ink tag antennae by printing converter factories so there is no need for any conventional electronic assembly.  It would be a significant cost savings if an RF test engineer was not retained on a full time basis in a printing converter factory.  Hence there is a need for tag read range test equipment that can automatically calibrate itself to adapt to a large variety of tag shapes.

                    Figure 1 illustrates a typical attribute read range test for either inductively-coupled tags or capacitively-coupled (BiStatix®) tags.  In this example, the reader 2 contains an AC excitation source 4 which is set at it’s maximum continuous exciter amplitude A4 resulting in a maximum exciter field F4 produced by an exciter antenna 3.  The AC amplitude vs. time graph on the right of Figure 1 illustrates that the exciter amplitude A4 does not change over time.  The tag under test 1 is placed at a specified distance within the excitation field F4 from the reader 2 which results in a “pass” indication if the tag 1 is within specification.


Figure 2


 Figure 3

                    Figure 2 illustrates that if the reader excitation source 4 is reduced to an amplitude A3 an attribute read range test may be performed if the tag under test 1 is moved closer to the reader excitation antenna 3 and within the excitation field F3.  The graph on the right side of Figure 2 illustrates that again the reader AC excitation source 4 output at the antenna 3 is kept constant over time.

                    Figure 3 illustrates the basic concepts of read range test autocalibration.  The purpose of the autocalibration sequence is to allow the reader 2 to automatically select the correct excitation amplitude to be generated by the excitation source 4 for a particular style of tag 1.  The procedure for autocalibration is outlined:

1.       A reference tag is chosen from an early prototype lot of tags...