Abstract: A magnetic/acoustic transducer is disclosed. The transducer can be used in security/smart tag applications. The transducer includes a sensor tag made of magnetic metallic glass having a relatively high magnetostriction and a relatively low coercivity. Driving signals are provided by an rf dipole loop antenna. The tag responds to the rf signals and converts the exciting magnetic field into acoustic signals via magnetoelastic coupling. That is, the tag is forced to vibrate in unison with the incident electromagnetic signals generating longitudinal acoustic waves along a length of the tag. This results in radiation of ultrasound waves in air which can then be detected and characterized using an ultrasound microphone or a piezoelectric sensor. The tag is provided having a length equal to one half or one quarter long of an acoustic wavelength so that an acoustic resonance condition is established to maximize the generation of ultrasound waves in air.

Abstract: A new technique is presented which exploits AC Hall effect in the characterization of layered semiconductor structures. The method involves the use of laser signals by means of optical fibers in the presence of a DC magnetic bias field. Upon incidence the polarization of the optical signal is rotated via a Lorentz force due to the AC Hall effect. As such, the reflected waves carry informations on the Hall mobility of the charge carriers. The calculations show that AC Hall reflection coefficient warrants sufficient intensity to be measured. Our theory is complete in the sense that depth profiling has been explicitly incorporated in the formulation.

Abstract: The present invention discloses a frequency tunable filter which includes an electromagnetic (E-M) wave propagation line which includes a microstrip and a ground plane in the substrate for transmitting a sequence of E-M signals via the propagation line. The E-M wave propagation line includes a frequency tuning mechanism, i.e., the magnetic layer, which is capable of utilizing a ferromagnetic anti-resonance frequency response to the E-M signals transmitted via the propagation line for controlling and frequency tuning the E-M signal transmission. In one of the preferred embodiments, the E-M wave propagation line includes a microstrip forming on the top surface of a dielectric or semiconductor substrate for receiving and transmitting the E-M signals and a ground plane forming on the bottom surface of the semiconductor substrate. And, the frequency tuning mechanism includes a ferromagnetic layer formed in the substrate between the microstrip and the ground plane.

Abstract: An array antenna includes a ferrite substrate having a two-dimensional planar array of antenna elements disposed over a first surface thereof and means for applying an external magnetic field having a magnitude and direction which can be varied at least in a plane in which the antenna elements lie. The amplitude and direction of the external magnetic biasing field is varied to control the relative phases between each of the plurality of antenna elements and to steer the direction of a main antenna beam in two dimensions.

Abstract: A planar SQUID magnetometer for detection and measurement of an applied magnetic flux is disclosed wherein a planar microwave-resonant element overlaps a Josephson device incorporated in a high-T.sub.c superconducting, thin-film SQUID device, thereby providing inductive coupling between the planar microwave-resonant element and the SQUID device. When the microwave-resonant element is excited by incident high-frequency microwave radiation, the intensity of reflected microwave radiation varies in response to a magnetic flux applied to the SQUID device in accordance with non-linear oscillatory behavior of the microwave-resonant element due to inductive loading by the SQUID device. The microwave-resonant element and the SQUID device are preferably fabricated photolithographically on a single substrate.

Abstract: A microstrip antenna includes a ferrite loaded substrate having a ground plane conductor disposed over a first surface thereof and having a strip conductor disposed over a second surface thereof. A DC magnetic field biasing circuit provides a directed DC magnetic field to the ferrite substrate such that the strip conductor radiates electromagnetic energy having circular polarization. In one embodiment, a ferrite material is disposed over the strip conductor to reduce the radar cross section of the antenna.