RFcalibration of saw interrogators

Abstract

Disclosed is an apparatus and methodology for insuring measurement accuracy and performance reliability in the operation of devices employed to interrogate SAW devices. The present subject matter relates to an arrangement and methodology that provides an interrogator paired together with a separate receiver, which may comprise a second interrogator, functioning together to perform a self-testing operation. The interrogator may correspond to more or less permanently paired set of devices physically placed in an array.

1 . A method for calibrating a drive-by interrogator, comprising the steps of: 
 providing a plurality of pairs of first and second interrogators, each interrogator having a transmitter portion and a receiver portion;    positioning each pair of interrogators in predefined spaced relationships;    transmitting a signal at a predetermined frequency and power level from the transmitter portion of a first interrogator of a first pair of said pairs of interrogators;    receiving the signal transmitted from the transmitter portion of the first interrogator by the receiver portion of the second interrogator of the first pair of said pairs of interrogators;    measuring selected characteristics of the signal received by the receiver portion of the second interrogator; and    comparing the measure characteristics of the signal received by the receiver portion of the second interrogator to a first set of predetermined reference values    whereby the result of the step of comparing provides an indication of the operational characteristics of said first and second interrogators.    
   
   
       2 . The method of  claim 1 , further comprising the steps of: 
 transmitting a signal at a predetermined frequency and power level from the transmitter portion of a second interrogator of the first pair of said pairs of interrogators;    receiving the signal transmitted from the transmitter portion of the second interrogator by the receiver portion of the first interrogator of the first pair of said pairs of interrogators;    measuring selected characteristics of the signal received by the receiver portion of the first interrogator; and    comparing the measure characteristics of the signal received by the receiver portion of the first interrogator to a second set of predetermined reference values    whereby the result of the step of comparing provides an indication of the operational characteristics of said first and second interrogators.    
   
   
       3 . The method of  claim 1 , further comprising the step of employing the receiver portion of at least one of the second interrogators to measure ambient radio frequency signal levels prior to the step of transmitting.  
   
   
       4 . The method of  claim 2 , further comprising the step of selecting the first and second set of predetermined reference values based on values established immediately following manufacture or calibration of the respective first or second interrogator.  
   
   
       5 . A method of operating a drive-by interrogator lane, comprising the steps of: 
 providing a plurality of interrogators each having a transmitter portion and a receiver portion;    configuring the plurality of interrogators as an array of paired interrogators forming spaced apart columns arranged such that the tires of a multi-wheeled vehicle may pass there between;    performing at least one diagnostic test on selected of the plurality of interrogators; and    permitting passage of a vehicle through the lane based upon the result of the diagnostic test.    
   
   
       6 . The method of  claim 5 , wherein the step of performing comprises the steps of: 
 transmitting a signal at a predetermined frequency and power level from the transmitter portion of a first interrogator of a first pair of said pairs of interrogators;    receiving the signal transmitted from the transmitter portion of the first interrogator by the receiver portion of the second interrogator of the first pair of said pairs of interrogators;    measuring selected characteristics of the signal received by the receiver portion of the second interrogator; and    comparing the measure characteristics of the signal received by the receiver portion of the second interrogator to a first set of predetermined reference values.    
   
   
       7 . The method of  claim 6 , wherein the step of performing further comprises the steps of: 
 transmitting a signal at a predetermined frequency and power level from the transmitter portion of a second interrogator of the first pair of said pairs of interrogators;    receiving the signal transmitted from the transmitter portion of the second interrogator by the receiver portion of the first interrogator of the first pair of said pairs of interrogators;    measuring selected characteristics of the signal received by the receiver portion of the first interrogator; and    comparing the measure characteristics of the signal received by the receiver portion of the first interrogator to a second set of predetermined reference values.    
   
   
       8 . The method of  claim 6 , wherein at least one of the measured selected characteristics is received signal strength, the method further comprising the step of: 
 adjusting the power level of the signal transmitted from the transmitter portion of a selected interrogator of the pair of interrogators based on the received signal strength.