Inventory control system using r.f. object identification

Abstract

An inventory control system for keeping track of inventory objects stored in a storage location. Each inventory object has an object circuit with a receiving antenna, a crystal with a specific resonant frequency, a rectifier for deriving D.C. power from R.F. signals of the same frequency received by the antenna, a unique identifier stored in non-volatile memory, a decoder for decoding identifier information contained in the received R.F signals, a transmitter and antenna for generating acknowledgment signals when an R.F signal of the same frequency as the crystal contains a matching identifier, and a microprocessor for controlling the active elements of the object circuit. A system generator generates search signals having a frequency component which specifies the class of objects under search and one or more identifier components which identify the objects being sought. A plurality of acknowledgment signal detectors distributed throughout the storage space feed back the acknowledgment signals to a system computer which correlates the acknowledgment signals with the storage areas of the object circuits generating the acknowledgment signals.

What is claimed is:  
     
         1 . An inventory control system comprising: 
 a signal generator for generating search signals containing a frequency component and an identifier component, said frequency component specifying a class of inventory objects and said identifier component specifying a particular inventory object in said class;    a plurality of system transmitting antennas coupled to said signal generator for broadcasting said search signals to storage areas for said objects:    a plurality of object circuits each associated to a different one of a plurality of inventory objects, each said object circuit having a receiving antenna, a crystal coupled to said receiving antenna with a resonant frequency equal to the class frequency assigned to the associated inventory object, a unique identifier for the associated inventory object permanently stored therein, means for comparing said unique identifier with the identifier component of a received signal of the resonant frequency of said crystal, and means for generating an acknowledgment signal when the stored identifier matches the received identifier component;    means for detecting an acknowledgment signal; and    means for correlating a detected acknowledgment signal with the location of the object circuit which generates the acknowledgment signal.    
     
     
         2 . The inventory control system of  claim 1  wherein said plurality of system transmitting antennas is grouped into a number of location groups each associated to a different storage area for said inventory objects; wherein said system generator includes means for coupling said search signals to individual ones of said location groups; and wherein said correlating means comprises means for detecting the location group to which said search signals are currently coupled when an acknowledgment signal is detected.  
     
     
         3 . The inventory control system of  claim 1  wherein each said object circuit includes a non-volatile memory for storing said unique identifier.  
     
     
         4 . The inventory control circuit of  claim 1  wherein each said comparing means includes a microprocessor.  
     
     
         5 . The inventory control system of  claim 1  wherein said storage areas are grouped in a number of storage compartments each having boundary wall regions; and wherein said system transmitting antennas are positioned at said boundary wall regions.  
     
     
         6 . A method of locating inventory objects in a storage region, said method comprising the steps of: 
 (a) generating search signals containing a frequency component and an identifier component, said frequency component specifying a class of inventory objects and said identifier component specifying a particular inventory object in said class;    (b) broadcasting said search signals to storage areas for said inventory objects;    (c) providing a plurality of object circuits each associated to a different one of a plurality of inventory objects, each said object circuit having a receiving antenna, a crystal coupled to said receiving antenna with a resonant frequency equal to the class frequency assigned to the associated inventory object, a unique identifier for the associated inventory object permanently stored therein, means for comparing said unique identifier object with the identifier component of a received signal of the resonant frequency of said crystal, and means for generating an acknowledgment signal when the stored identifier matches the received identifier component    (d) using each object circuit to generate an acknowledgment signal when the identifier stored therein matches the identifier component of a received search signal of the same frequency as the crystal frequency;    (e) detecting an acknowledgment signal; and    (f) correlating a detected acknowledgment signal with the location of the object circuit generating an acknowledgment signal.    
     
     
         7 . The method of  claim 6  wherein the step of correlating includes the steps of providing a plurality of system transmitting antennas grouped into a number of location groups each associated to a different storage area for said inventory objects, selectively coupling said search signals to said location groups, and detecting the location group to which said search signals are currently coupled when an acknowledgment signal is detected.  
     
     
         8 . The method of  claim 6  further including the step of using the electromagnetic energy contained in said search signals to power the object circuits.