Cart-based visibility system

Abstract

A cart has at least three wheels. It has one or more loop antennas, and a radio transceiver connected with the antennas. The antennas and transceiver operate at a frequency lower than 1 megahertz. The loop antennas are each at least 0.2 square meters in area. The cart is moved to an area such as a room, and the transceiver communicates with various RF tags in the room. Because of the antenna configuration, the portion of spectrum employed, and the power levels used, the cart is able to communicate with most if not all of the RF tags in the room. The cart can then be moved to another area such as another room, and the process repeated. In this way an inventory of tags can be made without expensive permanently installed infrastructure. The system is robust against interferers such as large metal objects and intervening objects.

1 . A method for use with a building comprising at least first second, and third rooms, the method comprising the steps of:
 providing a cart, the cart having at least three wheels, the cart having a first first loop antenna and a radio transceiver, the first loop antenna communicatively coupled with the radio transceiver, the radio transceiver operating at a frequency lower than 1 megahertz, the first first loop antenna having an area greater than 0.2 square meters;   placing the cart in the first room;   while the cart is in the first room, communicating by means of the first loop antenna with at least first, second, and third tags, each of the first, second, and third tags being at least five feet from the cart, the communication with the first, second, and third tags achieved without reorienting the first loop antenna, the communication with the first, second, and third tags each yielding an identification of each of the first, second, and third tags;   moving the cart to the second room;   while the cart is in the second room, communicating by means of the first loop antenna with at least fourth, fifth, and sixth tags, each of the fourth, fifth, and sixth tags being at least five feet from the cart, the communication with the fourth, fifth, and sixth tags achieved without reorienting the first loop antenna, the communication with the fourth, fifth, and sixth tags each yielding an identification of each of the fourth, fifth, and sixth tags;   moving the cart to the third room;   while the cart is in the third room, communicating by means of the first loop antenna with at least seventh, eighth, and ninth tags, each of the seventh, eighth, and ninth tags being at least five feet from the cart, the communication with the seventh, eighth, and ninth tags achieved without reorienting the   
   
   
       1 . A method for use with a building comprising at least first second, and third rooms, the method comprising the steps of:
 providing a cart, the cart having at least three wheels, the cart having a first first loop antenna and a radio transceiver, the first loop antenna communicatively coupled with the radio transceiver, the radio transceiver operating at a frequency lower than 1 megahertz, the first first loop antenna having an area greater than 0.2 square meters;   placing the cart in the first room;   while the cart is in the first room, communicating by means of the first loop antenna with at least first, second, and third tags, each of the first, second, and third tags being at least five feet from the cart, the communication with the first, second, and third tags achieved without reorienting the first loop antenna, the communication with the first, second, and third tags each yielding an identification of each of the first, second, and third tags;   moving the cart to the second room;   while the cart is in the second room, communicating by means of the first loop antenna with at least fourth, fifth, and sixth tags, each of the fourth, fifth, and sixth tags being at least five feet from the cart, the communication with the fourth, fifth, and sixth tags achieved without reorienting the first loop antenna, the communication with the fourth, fifth, and sixth tags each yielding an identification of each of the fourth, fifth, and sixth tags;   moving the cart to the third room;   while the cart is in the third room, communicating by means of the first loop antenna with at least seventh, eighth, and ninth tags, each of the seventh, eighth, and ninth tags being at least five feet from the cart, the communication with the seventh, eighth, and ninth tags achieved without reorienting the first loop antenna, the communication with the seventh, eighth, and ninth tags each yielding an identification of each of the seventh, eighth, and ninth tags.   
   
   
       2 . The method of  claim 1  wherein the first, fourth, and seventh tags are each fixed respectively to the first, second, and third rooms, and wherein the second, third, fifth, sixth, eighth, and ninth tags are each attached to respective movable objects. 
   
   
       3 . The method of  claim 1  wherein the cart further comprises a second loop antenna not coplanar with the first loop antenna, the second loop antenna communicatively coupled with the radio transceiver, the method further comprising the steps of:
 selectively operatively coupling the first loop antenna and not the second loop antenna to the transceiver; and   selectively operatively coupling the second loop antenna and not the first loop antenna to the transceiver.   
   
   
       4 . The method of  claim 1  further comprising the steps of:
 when the cart is in the first room, cleaning the first room;   when the cart is in the second room, cleaning the second room; and   when the cart is in the third room, cleaning the third room.   
   
   
       5 . A system for use in a building, the building having at least first, second, and third rooms, the system comprising:
 a cart, the cart having at least three wheels, the cart having a first first loop antenna and a radio transceiver, the first loop antenna communicatively coupled with the radio transceiver, the radio transceiver operating at a frequency lower than 1 megahertz, the first first loop antenna having an area greater than 0.2 square meters; in the first room, at least first, second, and third radio tags, each disposed to receive signals from the cart at a frequency lower than 1 megahertz, each of the first, second, and third radio tags in radio communication with the cart when the cart is in the first room;   in the second room, at least fourth, fifth, and sixth radio tags, each disposed to receive signals from the cart at a frequency lower than 1 megahertz, each of the fourth, fifth, and sixth radio tags in radio communication with the cart when the cart is in the second room;   in the third room, at least sixth, seventh, and eighth radio tags, each disposed to receive signals from the cart at a frequency lower than 1 megahertz, each of the sixth, seventh, and eighth radio tags in radio communication with the cart when the cart is in the third room.   
   
   
       6 . The system of  claim 5  wherein the first, fourth, and seventh tags are each fixed respectively to the first, second, and third rooms, and wherein the second, third, fifth, sixth, eighth, and ninth tags are each attached to respective movable objects. 
   
   
       7 . The system of  claim 5  wherein the cart further comprises cleaning supplies. 
   
   
       8 . The system of  claim 5  wherein the cart further comprises a holder for a trash bag.