Position and electromagnetic field sensor

Abstract

A position and electromagnetic field sensor is provided. The sensor relies upon an oscillator such as a Robinson marginal oscillator to generate an rf or microwave electromagnetic field. As an inhomogeneously-shaped object, such as a metallic toothed wheel, for example, moves through the resultant field, the field experiences a change in electric or magnetic susceptibility. This in turn causes energy losses in the oscillator the magnitude of which can be output as a d.c. signal related thereto. To detect non-moving objects which nevertheless generate an electromagnetic field or have attached to them a source thereof, the sensor may also include a giant or colossal magnetoresistive structure located adjacent the oscillator coil, the structure having an imaginary magnetic susceptibility which is strongly dependent upon the magnitude and direction of the field generated by or at the object to be sensed.

1 . A susceptibility sensor for detecting changes in susceptibility caused by an object to be sensed, comprising: 
 an oscillator including a sensor electromagnetic field generator, the oscillator having a plurality of electrical properties; and    an output arranged to provide a signal which varies in dependence upon changes in at least one of the electrical properties of the said oscillator as a result of changes in electric or magnetic susceptibility presented to the electromagnetic field;    wherein the oscillator operates in the microwave frequency range and substantially at or above 1 GHz.    
   
   
       2 . The susceptibility sensor of  claim 1 , wherein the oscillator and output are provided by a microwave transistor arranged such that the changes in electric or magnetic susceptibility cause the microwave transistor to operate on a different part of its characteristics and hence draw a different d.c. current.  
   
   
       3 . The susceptibility sensor of  claim 1 , further comprising a sensor element placed in proximity with the sensor electromagnetic field generator, the sensor element having an electric or magnetic susceptibility that varies as a function of the magnitude and/or direction of an applied electromagnetic field.  
   
   
       4 . The susceptibility sensor of  claim 1 , wherein the sensor electromagnetic field generator is selected from a group consisting of a stripline and a transmission line segment.  
   
   
       5 . The susceptibility sensor of  claim 3 , wherein the sensor electromagnetic field generator is selected from a group consisting of a stripline and a transmission line segment.  
   
   
       6 . The susceptibility sensor of  claim 5 , wherein the sensor element is a magnetic film grown onto the stripline or transmission line segment.  
   
   
       7 . The susceptibility sensor of  claim 3 , wherein the sensor element is formed from a colossal magnetoresistive material.  
   
   
       8 . The susceptibility sensor of  claim 7 , wherein the colossal magnetoresistive material is lanthanum strontium manganite (LSMO).  
   
   
       9 . The susceptibility sensor of  claim 1 , wherein the object to be sensed is compositionally inhomogeneous.  
   
   
       10 . The susceptibility sensor of  claim 1 , wherein the object to be sensed is irregularly-shaped.  
   
   
       11 . The susceptibility sensor of  claim 9 , wherein the object to be sensed is flowing blood.  
   
   
       12 . The susceptibility sensor of  claim 1 , wherein the changes in electric or magnetic susceptibility are due to relative movement of the object to be sensed and the sensor.  
   
   
       13 . In combination, the susceptibility sensor of  claim 3 , and an object to be sensed, the object to be sensed having associated therewith an object electromagnetic field generator.  
   
   
       14 . The combination of  claim 13 , wherein the object electromagnetic field generator is selected from a group consisting of a permanent magnet and an electromagnet.  
   
   
       15 . A susceptibility sensor for detecting changes in susceptibility caused by an object to be sensed, comprising: 
 an oscillator including a sensor electromagnetic field generator, the oscillator having a plurality of electrical properties; and    an output arranged to provide a signal which varies in dependence upon changes in at least one of the electrical properties of the said oscillator as a result of changes in electric or magnetic susceptibility presented to the electromagnetic field;    wherein the sensor electromagnetic field generator is selected from a group consisting of a stripline and transmission line segment.    
   
   
       16 . A susceptibility sensor for detecting changes in susceptibility caused by an object to be sensed, comprising: 
 an oscillator including a sensor electromagnetic field generator;    a sensor element arranged in proximity with the sensor electromagnetic field generator, the sensor element having an electric or magnetic susceptibility that varies as a function of the magnitude and/or direction of an applied electromagnetic field; and    an output arranged to provide a signal which varies in dependence upon the change in the electrical properties of the said oscillator.    
   
   
       17 . The susceptibility sensor of  claim 16 , wherein the sensor is arranged such that a change in the magnitude or direction of the object electromagnetic field associated with the object to be sensed, as experienced by the said sensor element, causes a change in the electric or magnetic susceptibility which in turn causes at least one electrical property of the oscillator to be altered.