Reconfigurable scanner and RFID system using the scanner

Abstract

A scanner has plasma loop or plasma window antennas for selectively scanning for ID tags along distinct radials of the scanner. Scanner elements are made electromagnetically invisible to adjacent elements by removing power or lowering plasma densities so that the scanner elements do not interfere with its own operation. Activatable ID tags and a shipping container suitable for scanning with electromagnetic energy are also disclosed.

1. A reconfigurable scanner for scanning for ID tags containing scannable antennas oriented in multiple directions relative to the scanner, without need for physical movement of the scanner, the reconfigurable scanner comprising:
 a scanning element broadcasting a signal in a selected direction, the scanning element having a plurality of variable conductive elements; 
 control means for electrically controlling and changing the selected direction in which the scanning element broadcasts the signal by powering and unpowering the plurality of variable conductive elements; and 
 transceiver means for generating an electromagnetic wave and receiving a responsive electromagnetic wave signal from a sensed ID tag within an effective range of the scanner, whereby unpowered variable conductive elements do not cause any interference with the scanning signal. 
 
     
     
       2. A reconfigurable scanner according to  claim 1 , wherein the plurality of variable conductive elements are a plurality of plasma loop sensors. 
     
     
       3. A reconfigurable scanner according to  claim 2 , wherein the plasma loop sensors each comprise a loop antenna having at least a portion of which is an arcuate tube section containing an ionizable gas, such that the loop antenna is only conductive when the ionizable gas is ionized. 
     
     
       4. A reconfigurable scanner according to  claim 1 , wherein the scanning element comprises an antenna and an electromagnetic shield formed by the plurality of variable conductive elements, the electromagnetic shield intersecting transmission lobes of the antenna in at least the multiple directions being scanned. 
     
     
       5. A reconfigurable scanner according to  claim 4 , wherein the plurality of variable conductive elements are mounted in an array on a substrate forming the shield. 
     
     
       6. A reconfigurable scanner according to  claim 5 , wherein the substrate is a conductive metal. 
     
     
       7. A reconfigurable scanner according to  claim 4 , wherein the electromagnetic shield is formed by stacked layers of arrays of the variable conductive elements. 
     
     
       8. A scanner system comprising:
 a plurality of electromagnetically scannable ID tags; and 
 a reconfigurable scanner having a scanning element with a plurality of variable conductive elements switchable between electromagnetically active and electromagnetically invisible, control means for switching the variable conductive elements between electromagnetically active and electromagnetically invisible, and a transceiver means for generating and receiving an electromagnetic scanning signal in a direction determined by the control means, the scanning signal interacting with the scannable ID tags located in the direction of the scanning signal. 
 
     
     
       9. A scanner system according to  claim 8 , wherein the variable conductive elements are plasma loop sensors. 
     
     
       10. A scanner system according to  claim 8 , wherein the scanning element comprises an antenna and an electromagnetic shield formed by the plurality of variable conductive elements, the electromagnetic shield intersecting transmission lobes of the antenna in at least the multiple directions being scanned. 
     
     
       11. A scanner system according to  claim 10 , wherein the plurality of variable conductive elements are mounted in an array on a substrate forming the shield. 
     
     
       12. A scanner system according to  claim 11 , wherein the substrate is a conductive metal. 
     
     
       13. A scanner system according to  claim 10 , wherein the electromagnetic shield is formed by stacked layers of arrays of the variable conductive elements. 
     
     
       14. A scanner system according to  claim 8 , wherein at least one of the plurality of ID tags comprise an antenna and a code connected with the antenna for detection and reading by the reconfigurable scanner. 
     
     
       15. A scanner system according to  claim 14 , wherein the at least one ID tag further comprises a power source for powering the antenna into an active state. 
     
     
       16. A scanner system according to  claim 15 , wherein the power source is external of the ID tag. 
     
     
       17. A scanner system according to  claim 14 , wherein the antenna of the at least one ID tag is a plasma loop, and the at least one ID tag further comprises a power source for weakly or partially ionizing a plasma in the plasma loop, whereby the plasma loop remains electromagnetically invisible until external energy is received by the plasma. 
     
     
       18. A scanner system according to  claim 17 , wherein the external energy is provided by the scanning signal. 
     
     
       19. A scanner system for detecting the contents of a shipping container, the system comprising:
 a plurality of slots formed in the shipping container for permitting a selected bandwidth of electromagnetic wave to penetrate the shipping container; 
 at least one electromagnetically scannable ID tag associated with the contents of the shipping container; and 
 a reconfigurable scanner having a scanning element with a plurality of variable conductive elements switchable between electromagnetically active and electromagnetically invisible, control means for switching the variable conductive elements between electromagnetically active and electromagnetically invisible, and a transceiver means for generating and receiving an electromagnetic scanning signal, the scanning signal having a frequency within the selected bandwidth for penetrating the shipping container to detect the at least one ID tag. 
 
     
     
       20. A scanner system according to  claim 19 , wherein the shipping container comprises dielectrics on the interior of the container for damping resonant signals. 
     
     
       21. A scanner system according to  claim 19 , wherein the slots are formed by dielectric materials. 
     
     
       22. A scanner system according to  claim 19 , wherein the slots are formed by one of variable dielectric materials surrounded by conductive material and fixed dielectric materials surrounded by variable conductive material. 
     
     
       23. A reconfigurable scanner for scanning for ID tags containing scannable antennas oriented in multiple directions relative to the scanner, without need for physical movement of the scanner, the reconfigurable scanner comprising:
 a scanning element broadcasting a signal in a selected direction, the scanning element having a plurality of variable conductive elements;   a switch that electrically controls and changes the selected direction in which the scanning element broadcasts the signal by powering and unpowering the plurality of variable conductive elements; and   a transceiver that generates an electromagnetic wave and receives a responsive electromagnetic wave signal from a sensed ID tag within an effective range of the scanner, whereby unpowered variable conductive elements do not cause any interference with the scanning element.   
     
     
       24. A reconfigurable scanner according to claim 23 wherein the plurality of variable conductive elements are a plurality of plasma loop sensors. 
     
     
       25. A reconfigurable scanner according to claim 24 wherein the plasma loop sensors each comprise a loop antenna having at least a portion of which is an arcuate tube section containing an ionizable gas, such that the loop antenna is only conductive when the ionizable gas is ionized. 
     
     
       26. A reconfigurable scanner according to claim 23 wherein the scanning element comprises an antenna and an electromagnetic shield formed by the plurality of variable conductive elements, the electromagnetic shield intersecting transmission lobes of the antenna in at least the multiple directions being scanned. 
     
     
       27. A reconfigurable scanner according to claim 26 wherein the plurality of variable conductive elements are mounted in an array on a substrate forming the shield. 
     
     
       28. A reconfigurable scanner according to claim 26 wherein the electromagnetic shield is formed by stacked layers of arrays of the variable conductive elements. 
     
     
       29. A reconfigurable scanner according to claim 23 wherein said plurality of variable conductive elements are of at least two dimensional configurations. 
     
     
       30. A steerable antenna for directing the sensitivity of a scanner that scans for ID tags, said steerable antenna comprising:
 an omnidirectional antenna having a first axis,   an annular shield having a longitudinal axis parallel to said first axis, said annular shield positioned a selected distance from said first axis, said annular shield having a plurality of elements, each one of said plurality of elements including a plasma element that is variably conductive between a conducting state and a non-conducting state, said annular shield allowing passage of a signal in a selected radial direction relative to said first axis; and   a switch configured to control each one of said plurality of elements between said conducting state and said non-conducting state.   
     
     
       31. The steerable antenna of claim 30 wherein each said plasma tube has a plasma density sufficient to reflect a signal at a selected frequency, said omnidirectional antenna operable at said selected frequency. 
     
     
       32. The steerable antenna of claim 30 wherein each said plasma tube has a plasma density less than that necessary to reflect a signal at a selected frequency, said omnidirectional antenna operable at said selected frequency. 
     
     
       33. The steerable antenna of claim 30 wherein each said plasma tube has a plasma density less than that necessary to reflect a signal at a selected frequency and said switch operates at a speed wherein said selected radial direction is changeable between a first and a second radial direction in less than a millisecond. 
     
     
       34. The steerable antenna of claim 30 wherein said selected distance is a multiple of one wavelength of a signal to which said omnidirectional antenna is responsive. 
     
     
       35. The steerable antenna of claim 30 wherein said selected distance is greater than one wavelength of a signal to which said omnidirectional antenna is responsive. 
     
     
       36. The steerable antenna of claim 30 wherein said plurality of elements are individually made to conduct at a plurality of frequencies. 
     
     
       37. The steerable antenna of claim 30 wherein each one of said plurality of elements is substantially parallel to said first axis. 
     
     
       38. The steerable antenna of claim 30 wherein each one of said plurality of elements is a ring that encircles said first axis, said rings being stacked to form a cylindrical shape. 
     
     
       39. The steerable antenna of claim 30 wherein said annular shield has a substantially cylindrical shape. 
     
     
       40. The steerable antenna of claim 30 wherein said annular shield has a substantially spherical shape. 
     
     
       41. The steerable antenna of claim 30 wherein said plurality of elements includes a first group of elements and a second group of elements, said first group of elements having a substantially cylindrical shape, said second group of elements having a substantially cylindrical shape, said first group of elements positioned inside said second group of elements. 
     
     
       42. A pulsed scanner for scanning for ID tags containing scannable antennas, said pulsed scanner comprising:
 a scanning element responsive to a signal having a selected bearing, said scanning element having a plurality of variable conductive elements;   a switch configured to electrically control and change a direction to which said scanning element is responsive by powering and unpowering selected ones of said plurality of variable conductive elements, each one of said plurality of variable conductive elements including a plasma element; and   a transceiver connected to said scanning element, said transceiver configured to generate an electromagnetic wave signal and receive a responsive electromagnetic wave signal, said responsive electromagnetic wave signal received by one of said plurality of variable conductive elements when said plasma element is in an afterglow state.   
     
     
       43. The pulsed scanner of claim 42 wherein said plasma element includes an energized state and said afterglow state, said energized state resulting from an ac bipolar pulse applied to said plasma element. 
     
     
       44. The pulsed scanner of claim 43 wherein said ac bipolar pulse has a frequency greater than an ion acoustic wave frequency. 
     
     
       45. A pulsed scanner for scanning for ID tags containing scannable antennas, said pulsed scanner comprising:
 a scanning element receiving a signal from a selected direction, said scanning element having a plurality of variable conductive elements;   a switch that electrically controls and changes a direction to which said scanning element is responsive by powering and unpowering selected ones of said plurality of variable conductive elements, each one of said plurality of variable conductive elements including a plasma element, each said plasma element being powered by a pulse, said pulse being an ac bipolar pulse; and   a transceiver connected to said scanning element, said transceiver configured to generate an electromagnetic wave signal and receive a responsive electromagnetic wave signal.   
     
     
       46. The pulsed scanner of claim 45 wherein said ac bipolar pulse has a frequency greater than an ion acoustic wave frequency.