The exemplary system and method for the characterization procedures for complex permittivity of a dielectric material at radio frequencies, including microwave and millimeter-wave wavelengths. The exemplary system and method employ a highly resonant periodic array affixed or placed in proximity thereto to provide a frequency response that varies based on the constituent electromagnetic properties of a sample of dielectric material.

Methods and systems for detection of threats in secure areas are disclosed. Microwaves are transmitted into high traffic areas and are reflected off or transmitted through targets within that area. The resulting signals are detected at receiving antennas which are designed to have a high cross-polarization discrimination (XPD) such that co- and cross-polarizations of the resulting signals are separable for further processing. The receiving antennas of the present invention comprise elliptical antennas with a double-ridged waveguide on the interior and a conically-shaped exterior. This particular design for the receiving antennas allows to technologically obtain an XPD of about 30 dB or more for solid angles measured from a receiving antenna's boresight (the main lobe axis), and formed by rotating the corresponding 30-degree planar angle around the main lobe axis, the solid angles measuring approximately 0.84 sr, in a frequency range between 9.5 and 20 GHz.

In a method for determining at least one physical parameter, a sensor unit which is activated by at least one periodic excitation (1.4) is provided, wherein the sensor unit has at least one detection region in which changes of the parameter in the surroundings of the sensor unit lead to output signal (1.7) from the sensor unit. The sensor unit is wired such that if there are no changes of the parameter in the detection region the output signal (1.7) is a zero signal or virtually a zero signal at the output of the sensor unit, whereas if there are changes of the parameter in the detection region the output signal (1.7) is a signal that is not zero and has a specific amplitude and phase. In a closed control loop, the non-zero signal in the receive path is adjusted to zero using a control signal to achieve an adjusted state even in the presence of changes of the parameter in the detection region. The control signal is evaluated in order to determine the physical parameter. The output signal (1.7) from the sensor unit is reduced substantially to the fundamental wave of the excitation (1.4) and the output signal (1.7) is controlled to zero in the entire phase space by means of at least one pulse width modulation. A temperature-stable, fully digital measuring system is provided as a result of the fact that the at least one pulse width modulation itself generates a correction signal with a variable pulse width and possibly a variable phase which is then added to the output signal (1.7) from the sensor unit and the output signal is thereby controlled to zero in the entire phase space, wherein the pulse width of the correction signal and/or the phase of the correction signal is/are determined by the deviations of the output signal (1.7) from zero.

A metal detection apparatus (9) is tested with a test device (7) having at least one test article (79), movable through a detection zone (60). The test article is moved through the detection zone along a first transfer axis (ca) and a first input signal is measured. A first threshold (th1) is determined, where an amplitude of the first input signal exceeds the first threshold (th1). Then, an identical test article is moved through the detection zone along a further transfer axis (ta; . . . ) and a further input signal is measured and a further threshold (th2; . . . ) is determined, where an amplitude of the further input signal exceeds the further threshold (th2; . . . ). The first or further threshold (th1; th2; . . . ) is selected in the signal processing path (4) whenever the test article is moved along the related transfer axis (ca; ta; . . . ).

A measuring system for determining the specific electrical conductivity of a medium in a vessel, comprising an inductive conductivity sensor with at least one transmitter coil that emits an input signal into the medium and a receiver coil connected to the transmitter coil via the medium that delivers the output signal, a temperature sensor for measuring the temperature of the medium, and a data processing unit that determines the conductivity of the medium using the input signal, the output signal, and the temperature provided. The system is characterized by the fact that the conductivity sensor and the temperature sensor are designed as non-invasive sensors.

In a method for determining at least one physical parameter, a sensor unit which is activated by at least one periodic excitation (1.4) is provided, wherein the sensor unit has at least one detection region in which changes of the parameter in the surroundings of the sensor unit lead to output signal (1.7) from the sensor unit. The sensor unit is wired such that if there are no changes of the parameter in the detection region the output signal (1.7) is a zero signal or virtually a zero signal at the output of the sensor unit, whereas if there are changes of the parameter in the detection region the output signal (1.7) is a signal that is not zero and has a specific amplitude and phase. In a closed control loop, the non-zero signal in the receive path is adjusted to zero using a control signal to achieve an adjusted state even in the presence of changes of the parameter in the detection region. The control signal is evaluated in order to determine the physical parameter. The output signal (1.7) from the sensor unit is reduced substantially to the fundamental wave of the excitation (1.4) and the output signal (1.7) is controlled to zero in the entire phase space by means of at least one pulse width modulation. A temperature-stable, fully digital measuring system is provided as a result of the fact that the at least one pulse width modulation itself generates a correction signal with a variable pulse width and possibly a variable phase which is then added to the output signal (1.7) from the sensor unit and the output signal is thereby controlled to zero in the entire phase space, wherein the pulse width of the correction signal and/or the phase of the correction signal is/are determined by the deviations of the output signal (1.7) from zero.

A sensor apparatus includes a sensor head and a measurement unit. The sensor head includes a first probe and a second probe. The first probe includes a first tiny antenna section for transmission and a second tiny antenna section for transmission. The second probe is arranged at a predetermined distance from the first probe, and includes a first tiny antenna section for reception and a second tiny antenna section for reception. The measurement unit generates a measurement signal that includes information regarding characteristics of a propagation of an electromagnetic wave in a medium between the first tiny antenna section for transmission and the first tiny antenna section for reception, and information regarding characteristics of the propagation of the electromagnetic wave in the medium between the second tiny antenna section for transmission and the second tiny antenna section for reception. The first probe and the second probe have different probe lengths, or a distance between the first tiny antenna section for transmission and the first tiny antenna section for reception, and a distance between the second tiny antenna section for transmission and the second tiny antenna section for reception are different from each other.

To detect the amount of degradation substance contained in oil.

The present oil state detection apparatus includes an oscillation circuit having a coil and a capacitor and a detection device. Any one of the coil or the capacitor is immersed in oil. The detection device detects the amount of degradation substance contained in the oil based on the value of change in the oscillatory frequency of the oscillation circuit in a predetermined period.