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. The measured ultrasound signal is locked in phase with the excitation or reference signal for sensitive long-range detection. The tag can operate in a magnetized or a demagnetized state to stimulate binary signals for security-tag applications. Tags of different length and/or geometry can be deployed in combination so that the tag transducer produces unique and distinguishable frequency spectrums to be used as smart tags.
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.
Abstract:
Disclosed is a method for improving the sensitivity of a fluxgate magnetometer for which high-order harmonics are detected and utilized in determining a weak external magnetic field expressed in the core region. These harmonic signals are processed coherently so as to increase the signal-to-noise ratio, since noise can only add to the signal incoherently at these harmonic frequencies. Also disclosed is a method for improving the sensitivity of a fluxgate magnetometer for which the technique of waveform autocorrelation is used in determining a weak external magnetic field expressed in the core region. By convolving the gated signal with a waveform duplicating the signal itself, noise content is effectively suppressed, thereby increasing the resolution power of the fluxgate magnetometer.
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:
Disclosed is a method and an apparatus enabling water-conditioning processes to be performed using a heater initially equipped with an aquarium tank for the purpose of supplying heat. Instead of allowing heat to propagate globally, reactor housing is introduced in the tank enclosing the heater so as to form a localized hot zone. The temperatures of the hot zone are maintained at high degrees sufficient to initiate various water-conditioning processes with efficiency, including alga control, ammonia control, water-hardness control, and sterilization. The construction of the reactor housing is simple and inexpensive, and its geometry is compatible to a heater which can be purchased commercially. In short, multiple functions are added to a heater installed in an aquarium, performing water-conditioning processes in addition to the basic task of supplying heat, allowing water quality of the aquarium to be improved and maintained.
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:
Disclosed is one method and one apparatus which teach improved techniques in using a shaped bias magnetic field over the active region of a ferrite stripline circulator/isolator circuit. The axial component of the bias field is decreased from the center toward edge, thus it is able to accommodate the accompanying changes in magnetization. This fulfills the requirements that frequencies are scaled with distances thereby warranting broadband operation. Furthermore, the radial component of the bias field is reduced, so as to minimize the generation of non-circulation volume modes. The discontinuity in magnetization distributed over the circulator/isolator active region is reduced, so as to minimize the generation of magnetostatic surface modes. The resultant circulator/isolator performance can thus show a broad bandwidth with improved characteristics in insertion loss and in isolation.
Abstract:
Disclosed is a method for establishing and utilizing electronic tracks on roads for ground vehicles so as to ease the driving task with added safety and efficiency. Electronic tracks define traces on roads guiding the movement of a ground vehicle in as much as the same way that railroad tracks confine the movement of a train. Speed control can be achieved by using equipments detecting the driving conditions and the road environment along with the gliding action of the ground vehicle on electronic tracks. Automation in driving is thus possible, at least partially. Electronic map can be constructed consisting of many of the electronic tracks. Based upon both the static and dynamic information on roads, an electronic map is able to configure an optimal route connecting two addresses with the shortest time in traveling.