Auto hang tag with radio transponder

Abstract

There is disclosed an automobile hang tag for use in parking control and the like with an integral radio transponder, together with interrogator apparatus associated therewith in a system for parking control or other purposes. The detection range for the RFID interrogator and transponder is at least about six meters (20 feet) to enable rapid control monitoring of parking facilities from a moving vehicle through the back window or front windshield of parked vehicles. Reliable and trouble-free monitoring of the hang tags in a customary rear view mirror location is facilitated by employing directional antennas in the RFID hang tags, increasing the antenna gain while suppressing false signals and noise and improving the range-to-power ratio for the system. The RFID hang tags may be battery powered but are preferably unpowered RFID transponders. Suitable directional antennas employed may include Yagi antennas, log periodic antennas, stacked dipole antennas, spiral or slot antennas or other monodirectional or bidirectional antennas, preferably those suitable for selected frequencies within the 1,000 megahertz to 10,000 megahertz range.

1. Vehicle monitoring apparatus using radio frequency identification technology comprising:
 a transportable RFID interrogator having a transceiver with a transmitting antenna;  
 a plurality of individually encoded auto hang tags incorporating RFID transponders and suitable for affixing temporarily in a vehicle interior, each of said hang tags having at least one flat surface area with visible indicia thereon and configured to be affixed with the normal to said flat surface generally along a horizontal sight path through a window of said vehicle;  
 each said RFID transponder including a memory element having encoded readable data, a controller microcircuit connected to read from said memory element, a modulator configured to be operated by said controller microcircuit, a receiver with at least one directional antenna coupled to provide a received signal to said control microcircuit, and a coupling between said modulator and said at least one horizontally directional antenna for causing transmission therefrom to be modulated in response to data read from said memory element.  
 
     
     
       2. Apparatus as recited in  claim 1  wherein said at least one directional antenna has directionality favoring the direction of a normal to said flat surface and disfavoring directions 45 degrees or more horizontally from said normal. 
     
     
       3. Apparatus as recited in  claim 2  wherein one said directional antenna also has vertical directionality favoring a horizontal direction and disfavoring a vertical or partially vertical direction. 
     
     
       4. Apparatus as recited in  claim 1  wherein said directional antenna comprises an active dipole element and, at least one director element horizontally spaced from said active dipole element. 
     
     
       5. Apparatus as recited in  claim 1  wherein said directional antenna comprises a plurality of active dipole elements. 
     
     
       6. Apparatus as recited in  claim 1  wherein said directional antenna comprises an elongated conductive element having a convoluted shape in a plane perpendicular to the favored direction of directionality. 
     
     
       7. Vehicle monitoring apparatus using radio frequency identification technology comprising:
 a transportable RFID interrogator having a transceiver with a directional transmitting antenna;  
 a plurality of individually encoded auto hang tags incorporating RFID transponders and suitable for affixing in a vehicle near a rear view mirror, each of said hang tags having at least one flat surface area with visible indicia thereon and configured to be affixed with the normal to said flat surface generally parallel to the vehicle longitudinal axis;  
 each said RFID transponder including a micro-circuit memory having encoded readable data, a controller microcircuit connected to read from said memory, a modulator configured to be operated by said controller microcircuit, a receiver with a horizontally directional antenna coupled to provide a received signal to said control microcircuit, and a coupling between said modulator and said horizontally directional antenna for causing transmission therefrom to be modulated in response to data read from said memory element.  
 
     
     
       8. Apparatus as recited in  claim 7  wherein one said horizontally directional antenna is horizontally polarized favoring a direction normal to said flat surface and disfavoring directions 45 degrees horizontally from the normal. 
     
     
       9. Apparatus as recited in  claim 8  wherein one said horizontally directional antenna also has vertical directionality favoring a horizontal direction and disfavoring a vertical or partially vertical direction. 
     
     
       10. Apparatus as recited in  claim 7  wherein one said horizontally directional antenna also has vertical directionality favoring a horizontal direction and disfavoring a vertical or partially vertical direction. 
     
     
       11. Apparatus as recited in  claim 7  wherein said horizontally directional antenna comprises an active dipole element and at least one director element horizontally spaced from said active dipole element. 
     
     
       12. Apparatus as recited in  claim 7  wherein said horizontally directional antenna comprises a plurality of active dipole elements. 
     
     
       13. Apparatus as recited in  claim 7  wherein said horizontally directional antenna comprises an elongated conductive element having a convoluted shape in a plane perpendicular to the favored horizontal direction of directionality. 
     
     
       14. In a vehicle monitoring apparatus using radio frequency identification technology an auto hang  identification tag with radio transponder comprising:
 a hang  tag body having at least one flat surface area with visible indicia thereon and configured to reside at a rear view mirror  be oriented with the normal to said flat surface generally parallel to the  a vehicle longitudinal  horizontal axis;  
 an RFID transponder embodied in said hang tag body including a microcircuit memory element having encoded readable data, a controller microcircuit connected to read from said memory, a modulator configured to be operated by said controller microcircuit, a receiver coupled to provide a received signal to said controller microcircuit, said receiver having a directional antenna with horizontal directionality favoring the  a first direction of a normal  relative to said flat surface and disfavoring directions 45 degrees or more horizontally from said normal  first direction, and a coupling of said modulator to said at least one directional antenna for causing transmission therefrom to be modulated in response to data read from said memory.  
 
     
     
       15. Apparatus as recited in  claim 14  wherein one  said directional antenna also has vertical directionality favoring a horizontal direction and disfavoring a vertical or partially vertical direction. 
     
     
       16. Apparatus as recited in  claim 15  wherein said directional antenna comprises a plurality of dipole elements. 
     
     
       17. Apparatus as recited in claim  14    15  wherein said directional antenna comprises an active dipole element and at least one director element horizontally spaced from said active dipole element. 
     
     
       18. Apparatus as recited in claim  14    15  wherein said directional antenna comprises a plurality of active dipole elements. 
     
     
       19. Apparatus as recited in claim  14    15  wherein said directional antenna comprises an elongated conductive element having a convoluted shape in a plane perpendicular to the favored direction of directionality. 
     
     
       20. Apparatus as recited in  claim 15  wherein said directional antenna includes at least three dipole elements with at least one being active and at least one being inactive.