Meter and method for in situ measurement of the electromagnetic properties of materials using cutoff frequency characterization and analysis

The present invention provides an apparatus and method for the measurement of, for example, the moisture in a material or, more generally, for the measurement of any material parameter which may be inferred by measuring the electromagnetic properties of the material under investigation. The electromagnetic properties of use in the present invention are complex electrical permittivity or the magnetic permeability of the material. The meter apparatus of the present invention comprises a controllable source of electromagnetic energy having stable selectable frequency. The controllable source of electromagnetic energy is coupled to a material measurement chamber by means of probes, loops, antennas, apertures or other structures so as to establish an electromagnetic wave inside the measurement chamber thereby causing the wave to interact with the material contained in the chamber. Its preferred structure comprises coupling of microwave energy from a coaxial transmission line to the measurement chamber over a multi-octave bandwidth via an intermediate microstrip to slotline coupling circuit.