Abstract: Method and apparatus for in vivo or in vitro selective deposition of microwave power patterns in lossy dielectric materials, particularly biological tissue. Configured as a needle-like probe, a miniature coaxial cable (1) having a circumferential gap (12) in the shield (2) is wrapped with an electrically thin dielectric substrate (18). The cable center conductor (6) extends immediately past gap (12) and is shorted to cable shield (2). A thin conductive dipole resonator (21) is positioned on substrate (18) and over gap (12) to achieve inductive coupling between the cable center conductor (6) and the dipole resonator (21) through gap (12). The ends of the dipole resonator (21) are capacitively (22) loaded so as to make the current on resonator (37) more uniform and to greatly reduce and stabilize the resonant frequency to be essentially insensitive to the dielectric properties of the surrounding material.

Abstract: A highly sensitive, direct-contact, in situ sensor for nondestructively measuring or monitoring the complex dielectric and conductive properties of solids, liquids, or gasses at microwave frequencies. A metal microstrip dipole resonator (11) is etched on the surface of a dielectric substrate (12) which is bonded to a copper ground plane (14). The dipole resonator is electromagnetically driven by mutual inductive coupling to a short nonresonant feed slot (13) formed in the ground plane (14). The slot (13) is driven by a coaxial feed line (7) or a microstrip feed line (16) extending from a swept microwave frequency source (2) which excites the incident wave (17). Alternatively, the metal resonator is omitted and the length of the slot (15) is increased so that it becomes the resonator. In use, the sensor is placed in close physical contact with the test material (9) having complex dielectric constant .epsilon.* (=.epsilon.'-j.epsilon.") or conductivity .sigma..

Abstract: The invention is method and apparatus for in situ mechanical adjustment of electromagnetic power coupled through an aperture or slot. In its preferred form this adjustment of coupling is achieved by electrically connecting two thin, curved conductive leaf springs (20) to ground plane (14) at the ends of the coupling aperture or slot (12). The springs (20) are curved so as to bend away from the center of the aperture or slot opening (12). The aperture or slot is usually enclosed by a metal backing cavity (22) to prevent radiation from the rear of the aperture or slot and to provide a method for mechanically adjusting the position of springs (20) over the aperture or slot (12), e.g., by adjustment of screws (24). By advancing or retracting screws (24), leaf springs (20) are caused to progressively cover or uncover aperture or slot (12), thereby adjusting the electric field across the aperture or slot (12) and the coupled electromagnetic power through the aperture or slot (12).

Abstract: Method and apparatus for in vivo or in vitro sensing of complex dielectric properties of lossy dielectric materials, particularly biological tissue. Configured as a needle-like dielectric sensor, a coaxial cable (1) having a circumferential gap (12) in the shield (2) is wrapped with an electrically thin dielectric substrate (18). The cable center conductor (6) extends immediately past gap (12) and is shorted to cable shield (2). A thin conductive dipole resonator (16) is positioned on substrate (18) and over feed gap (12) to achieve inductive coupling between the cable center conductor (6) and the dipole resonator (16) through gap (12). Superstrate (22), which could be a dielectric catheter, covers the entire sensor assembly (10). By measurement of the resonator resonant frequency and the input impedance matching factor at the resonant frequency, the real and imaginary dielectric components (.epsilon.', .epsilon.") of the test material into which the sensor is inserted are determined.