Abstract: Disclosed is a method for the discriminating of obstacles by means of a radar, and its different applications to the measurement of a liquid in a tank or vessel, or again to the elimination of unwanted or parasitic echos coming notably from the ground, for radars mounted on vehicles or controlling vehicle traffic. To implement the method, the obstacle to be discriminated must have a substantially plane surface. The disclosed method then consists in successively transmitting substantially plane waves at slightly different angular frequencies .omega..sub.i, each wave being furthermore sent with two different polarizations p and p' chosen in such a way that these different coefficients of reflection on the obstacles according to the incidence of the waves give a criterion of discrimination. The processing at reception depends on the use (measurement of distance, elimination of parasitic echos etc.).

Abstract: A method and apparatus for measuring a level of a material in a tank includes providing a stepped frequency microwave signal to an antenna of a transmitter and receiving in the antenna a received signal from a surface of the material at the level to be measured. A measuring signal containing ranging and calibrating signals is processed in even and odd sample sets input to contiguous narrowband filters formed digitally in a processor using DFT and other algorithms to form true in-phase and quadrature outputs. These outputs are combined and further processed using an interpolation algorithm to isolate ranging and calibration frequency components and to accurately measure the distances represented by such components. The calibration distance associated with the calibration frequency component is compared to a known delay line length and any determined error is used to correct the ranging distance associated with the ranging frequency component.

Abstract: A method and apparatus for the measuring of a delay in a delay circuit by making a continuous frequency measurement is proposed. The phase-locking of a variable frequency signal applied to the delay circuit allows the user to significantly improve the precision and accuracy of the time delay measurement. A scheme to extract the number of cycles stored in the delay circuit is also disclosed.

Abstract: An electrical device for measuring the liquid level in industrial tanks and the like with a microwave transmitter and receiver and a waveguide provided with an aperture and an antenna. The signal reflected from the liquid surface and the transmitted signal are fed to a frequency conversion stage (8), whose low-frequency output signal is sent via an A/D converter (12) to a microprocessor calculating the fill level. To reduce the effect of interference frequencies produced by reflection of microwaves in the optical aperture, etc., a band-pass filter (9,10) with a lower limiting frequency selected to attenuate the low-frequency interference frequencies is placed between the frequency conversion stage (8) and the A/D converter (12). The lower limiting frequency can either be controlled with microprocessor (13) or the band-pass filter (9, 10) has adjustable limiting frequencies.

Abstract: A monostatic frequency modulator continuous wave radar for detecting and determining the distance to near range objects. A temperature compensated one port Z-network is provided to generate a voltage of equal magnitude and opposite sign to that of the voltage reflected from the antenna.

Abstract: A point liquid level monitoring system includes a sensor removeably mounted to a liquid level device. The sensor is designed to direct a microwave signal from a transmitter through a window in the liquid level device. In one embodiment, the microwave signal is reflected off a surface in the device opposite the window and collected by a receiver. In another embodiment, the microwave signal is collected by a receiver mounted onto a second window opposite the first window through which the microwave signal is transmitted. When liquid is present in the liquid level device at or above the level of the transmitter and receiver, the microwave signal is attenuated as it passes through the liquid. Sensor electronics compare the received signal to a predetermined threshold level and provide an output indicating the presence or absence of liquid at the transmitter/receiver level.

Abstract: A microwave apparatus and method for ullage measurement of agitated materials is provided. The apparatus and method utilize a transformation of the reflected time domain signal into a frequency domain signal. The frequency domain signal is averaged using the natural, inherent weighting associated with the transformation to achieve a unique corrected result. The average frequency domain signal is then used to calculate the average distance for determining the ullage measurement.

Abstract: A method and system for monitoring the level of flowable material contained in a transportable vessel that utilizes microwave gauging technology. The system includes a microwave lens/seal assembly, a microwave transceiver assembly, a controller/processor assembly and a computer. The lens/seal assembly is permanently secured to the vessel. The microwave transceiver assembly is adapted to be releasably attached to the vessel. The controller/processor assembly and the computer may be located at a loading/unloading facility.

Abstract: First and second identical pseudo-random binary sequences are generated. The second sequence is delayed in a variable delay arrangement, and a reflected first sequence is compared with a delayed second sequence. The second sequence is delayed until the reflected sequence and the delayed sequence are coincident. The delay of the adjustable delay is equal to the travel time of the first sequence.

Abstract: Disclosed is a in-furnace slag level measuring method for measuring a slag level in a convertor and an apparatus therefor. A sublance and an antenna of a microwaver radar are arranged exchangeable therebetween so that the sublance and the antenna are alternatively inserted in to the convertor from about the convertor. The antenna is inserted into the convertor in first and middle stage of the refining operation of the converter to thereby measure the slag level, and the sublance is inserted into the convertor to thereby perform various measurement.

Abstract: An in-furnace level meter for measuring a slag level, or the like, in a convertor, and an antenna used therefore. An antenna position is controlled so that the distance between the antenna inserted in the convertor and the slag level can be established to be constant or within a predetermined range. A water-cooled structure antenna is used as the antenna.

Abstract: A device for gauging the level of a fluid in a container with a microwave signal is described. The device comprises a vertical tube (1) mounted in the container, and a transmitter and a receiver and an electronic unit for determining the level based on the reflex position of the microwave signal. The device is characterized particularly by a calibration device in the form of a polarization means (6, 7) for polarizing the microwave signal in two polarization planes separated from each other and at least one reflecting reactance (10) in the tube (1) arranged to give a substantially stronger reflex of the microwave signal in the first polarization plane than in the second.

Abstract: Disclosed is an in-furnace slag level measuring apparatus having a microwave radar for measuring a slag level in a convertor or the like. The level of a transmission signal or a reception signal is adjusted in accordance with the level of a detection signal so that the signal level in the microwave radar is adjusted to be constant. Further, the level measurement value and the detection signal are inputted and the level measurement values obtained in a predetermined time are subjected to averaging operation. In the averaging operation, when the detection signal is smaller than a set point, the averaging operation is performed while disregarding the level measurement value at that time.

Abstract: A device for gauging the level of a fluid in a container having a gas above the surface of the fluid. The device comprises a microwave transmitter transmitting a microwave radio signal through the gas to the surface and a receiver for receiving the microwave signal reflected by the surface. An electronic unit is arranged to calculate from the propagation time of the microwave signal a first distance from the transmitter to the surface of the fluid and thereby the level in the container. The microwave signal is preferably within the radar frequency range. A sound transmitter is also provided for transmitting a sound signal through the gas to the surface of the fluid and is capable of receiving a sound signal reflected from the surface of the fluid. A means is provided for correcting the first distance to a second corrected distance as a function of the microwave velocity and the known relation between the sound velocity and the microwave velocity.

Abstract: The device includes a radar antenna mounted at the inside end of an arm which can be horizontally inserted through the wall of the furnace above the loading surface, an electronic control and measuring unit placed outside the furnace, and one or two waveguides connecting the said antenna to the electronic unit through the arm. The waveguide or waveguides are duplicated by two reference waveguides of the same nature and of the same length but not connected to the said antenna systems in order to provide a forward and return path for a reference signal generated by the electronic unit and which remains correlated with the measurment signal to allow a better identification of the reflected signal.

Abstract: The device includes a transmitting antenna which also serves as a receiving antenna and a separate receiving antenna for receiving the signals transmitted by the transmitting antenna and reflected at the point of reflection, and two data processing units, one for the signals picked up by the transmitting and receiving antenna and transmitted through a circulator and a first mixer, the other for the signals picked up by the receiving antenna and transmitted through a second mixer. The distance measurement is computed using the signals picked up by the transmitting and receiving antenna for distances less than a predetermined threshold and using the signals picked up by the receiving antenna for distances greater than the predetermined threshold.

Abstract: A radar probe including several individual scanning antennas is mounted in the wall of the furnace above the loading surface and performs a two-dimensional scanning of the entire loading surface.

Abstract: The invention is a device for determining the thickness of radar absorption material coatings. The device comprises a radiating element assembly 22 for transmitting RF energy to and recovering reflected RF energy from the coating. A source of frequency modulated RF signal, including an FM ramp generator assembly 11, buffer amplifier assembly 13 and Gunn oscillator 16, is provided. A ferrite circulator 20 is adapted to direct the source of modulated RF signal to the radiating element assembly 22 and the reflected RF energy to a detector assembly. The detector assembly includes a Schottky detector 24, a video amplifier assembly 40, a converter/driver assembly 42, and a digital display 44, and is adapted to sense the reflected RF energy from the coating and provide a visual display in the form of a voltage inversely proportional to the amount of the reflected RF energy.

Abstract: A Gunn microwave transmitter/receiver is coupled to an antenna to transmit microwave signals perpendicularly to a surface of a motionless or a slow moving object and to receive waves reflected from the object. The frequency of the oscillator of the Gunn transmitter is controlled by the output of a sawtooth wave generator. Accordingly, the output of the transmitter is cyclically and linearly varied from a first transmitted frequency to a second transmitted frequency. An accurate timer cyclically resets the both the sawtooth generator and digital processing circuitry.The wave reflected from the object and the signal transmitted at the time of arrival of the reflected wave are processed to detect the difference between the reflected wave and the transmitted wave, or the first negative to positive zero crossing that occurs after reset. This event initiates a time window which is terminated at the end of the cycle in which the relationship is detected.

Abstract: The filling level meter for measuring the filling level in a container includes a transmitting and a receiving arrangement which directs sonic or ultrasonic pulses onto the filling material surface and receives the backscattered pulses reflected by the filling material surface and converts them to electrical reception signals. Connected to the transmitting and receiving arrangement is an evaluating circuit which in a signal processing path generates an envelope signal corresponding to the envelope of the reception signals, digitizes sampled values of the envelope signal, stores in a memory the digitized sampled values for creating a distance-dependent or travel-time-dependent amplitude profile of the measurement distance and evaluates the amplitude profile for determining the travel time of the most probable useful echo signal.

Abstract: A sweep frequency, continuous wave (CW) radar tank gauge (3) providing measurement of the level of tank contents or ullage (19), having greatly improved accuracy through improved methods of processing calibrate and return signals directed toward the surface of tank contents (20). Use of sweep synchronous measurement (46) of time domain calibrate/return difference signals (42) and time domain of a virtual "carrier" fundamental in the frequency domain, provide highly accurate measure of tank signal return times. The entire range of return signals is made available for processing and analysis (5), including distinguishable tank bottom reflections.

Abstract: A method an apparatus for measuring the distance to a target wherein FM wave is transmitted to the target and its reflected wave is received. A beat wave is then obtained using the thus-received wave and the FM wave. A sine wave is mixed with the beat wave and a first sideband wave of a plurality of sideband waves of the resultant mixed wave is obtained. Another sine wave is mixed with the sideband wave. Then, a second sideband wave of the thus-obtained mixed wave is separated and detected. In the above manner, phase modulation is applied directly to the above-described beat wave. Information pertaining to distance can then be obtained from the number of peaks of the thus-modulated beat wave. A microwave profile meter suitable for use in the determination of the surface profile of a burden in a blast furnace is also disclosed.

Abstract: A sweep frequency, continuous wave (CW) radar tank gauge (3) providing measurement of the level of tank contents or ullage (19), having greatly improved accuracy through improved methods of processing calibrate and return signals directed toward the surface of tank contents (20). Use of sweep synchronous measurement (46) of time domain calibrate/return difference signals (42) and determination of a virtual "carrier" fundamental in the frequency domain, provide highly accurate measure of tank signal return times. The entire range of return signals is made available for processing and analysis (5), including distinguishable tank bottom reflections.

Abstract: High amplitude signals reflected back to the horn radiator-receptor in a microwave tank-contents measuring assembly from the interface between a microwave dielectric lens and the tank-contents-atmosphere, which reflected signals mimic returning ranging signals and interfere with detection of returning legitimate ranging signals, are substantially canceled by incorporating in the lens which is plano-convex a thin layer of electrically conductive material in a plane parallel to the plano surface of the lens, said layer being formed from a uniform array of a repetitive pattern of regions containing the conductive material alternating with regions free of said material. One embodiment has an hexagonal array of circular conductive regions while another embodiment has the conductive material in the form of a rectilinear grid.

Abstract: The invention concerns a method and an apparatus for measuring the level of a material with microwave signals. The apparatus consists of a signal processing unit (10) and a transmitter unit (1) of known type. The transmitter unit produces a measuring signal having a frequency (f.sub.m) corresponding to the distance (H) to be measured and a reference signal having a frequency (f.sub.r) corresponding to an accurately known length (L). In the signal processing unit (10) the reference signal is multiplied by a selectable number (AQ) which is proportional to the quotient of an assumed value for the distance divided by the known length (L), after which the frequency is divided by a fixed number (Z) so that the frequency of the signal after multiplication and division becomes equal to the expected frequency of the measuring signal.

Abstract: A method and device for measuring the distance to an object, particularly the distance to the surface (17) of a liquid in a container (15). An antenna (11) is arranged a distance from and aimed against the surface, the antenna being connected to a measuring unit (12), a channel unit (13) and a control unit (14). A microwave signal with a predetermined frequency is generated in the measuring unit (12), of which a part is utilized as a reference signal, while a further part is input to the antenna (11) and transmitted against the surface (17). From the reflected signal received by the antenna and supplied to the measuring unit (12) and the reference signal, a function of the antenna input reflection coefficient is determined. This function is adapted to the current condition. A fourier transformation of a set of values of this function at a certain set of measuring frequencies is made, from which the distance to the surface is calculated.

Abstract: A method and apparatus provide for the determination of the rate-of-rise of the level of a liquid, such as molten metal in a mold, in a reliable, accurate, and flexible manner. Molten metal passes from a container through an adjustable valve in an orifice to a mold. A microwave generator is connected to a microwave antenna located above the mold for transmitting microwaves to the surface of the molten metal in the mold. A mixer/detector is operatively connected to the antenna, and a computer is operatively connected to the mixer/detector. The computer processes the mixed signal received from the mixer/detector after it is converted to a digital signal. This digital signal is responsive to the Doppler signal caused by change in the level of the metal in the mold. The rate-of-rise of the surface of the molten metal is calculated in response to the digital signal, and is displayed on a monitor.

Abstract: In a method of measuring the level of a flowing material kept in a container there is employed a microwave signal that is fed from a transmitter through a tubular waveguide (7) that extends vertically downwardly through the container and communicates therewith so that the surface (10) of the material in the waveguide follows the level of the surrounding material. The signal is reflected from the surface back up through the waveguide and is conducted to a receiver to be employed, after signal processing in an electronic unit, for determining the level of material in the container. The microwave signal is fed to the waveguide by way of a mode generator (11) that produces only one dominant propagation mode of the signal, the wavelength of which is smaller than the diameter of the waveguide (7).

Abstract: A method for measuring the water level in a well including the steps of radiating an electromagnetic wave to a gap between a boring drill rod and a casing pipe by using a transmitting antenna, receiving the electromagnetic wave reflected by a surface of the water level in the casing pipe by using a receiving antenna; then measuring a distance between the surface of the water level and the receiving antenna based on the going and returning time of the electromagnetic wave.