Abstract: Multiple bits of information may be conveyed by passive target material incorporating filaments of magnetizable material having different magnetization functions and, in particular, different coercivities. Detection of the presence or absence of the individual filaments may be done remotely by measuring induced flux B as a function of an externally imposed magnetic field waveform and subjecting the measured induced flux signal to differentiation or Fourier transform techniques.

Abstract: A method and apparatus for measuring the amount of free water contained within a substance includes a waveguide having front and back sides disposed opposite each other. The waveguide defines a chamber for propagating a microwave signal therethrough. The waveguide has an end perpendicular to the front and back sides which forms a short within the chamber. The front and back sides each have an aperture for passing a substance therethrough. A microwave signal in the frequency range of 10-25 gigahertz is directed through the chamber wherein the generated microwave signal is reflected back from the short of the end. The generated and reflected signals form a ratio which is used by a microprocessor along with the measurement from an adjacent sensor that provides a dielectric constant measurement corresponding to the density of the substance in order to determine a weight of the substance compensated for free water.

Abstract: High aspect ratio filaments of magnetic material are randomly dispersed in a non-magnetic matrix such as paper or plastic for part of a critical component of a manufactured product to permit remote sensing of the manufactured product by the application of an external oscillating magnetic field and the detection of the resulting induced magnetization. The material may be incorporated into a wide variety of products that must be remotely sensed.

Abstract: A magnetically variable inductor for high power, high frequency applications which includes a solenoid with a magnetic core therein, disposed coaxially around a conductor for carrying the high power, high frequency signal and a variable current source coupled with the solenoid so that a manipulation of the current through the solenoid results in a variable inductance for said conductor. Also disclosed are additional features of ferrite rings disposed around each end of the magnetic core, a shield disposed between the core and the solenoid, and a sheath disposed around the solenoid.