Valentin Magori

Novel FMCW radar system concept with adaptive compensation of phase errors

A new high-performance FMCW sensor system concept is presented. The approach is based on an adaptive signal processing scheme compensating phase errors caused by VCO phase noise as well as the non-linearity of the frequency modulation. The key component of the low-cost sensor is a SAW (surface acoustic wave) delay line representing a miniaturised high-precision radar reference path. A correction algorithm equalises the target signal according to the phase errors simultaneously measured with the reference path. Employing this method, an excellent range resolution as well as a high dynamic range and multi-target selectivlty is obtained, which has been experimentally demonstrated at millimetrewave frequencies.

Modified SiO2 aerogels as acoustic impedance matching layers in ultrasonic devices

Acoustic impedance matching between a transducer and the irradiated medium can be achieved using quarterwave or impedance gradient layers. SiO 2 aerogels are suitable materials for both purposes. In order to investigate matched transducers for air applications, sound intensity measurements were performed with and without aerogel quarterwave layer for different types of piezoceramic transducers. The measured gains in sound pressure level are compared with theoretical data derived from Masons equivalent circuit and from finite element simulations. Ways to employ aerogel gradient layers for the acoustic matching of piezoceramics and biological tissue are discussed. Such layers could be obtained by sintering aerogels in a temperature gradient. Under certain conditions, an energy transmission coefficient of more than 99% for all frequencies above a certain frequency, f 0 , is predicted with such systems.

Radio accessible SAW sensors for non-contact measurement of torque and temperature

Surface acoustic wave (SAW) based sensors can easily be interrogated by low power radio signals. They therefore are ideally suited for non-contact measurement of torque and temperature on rotating shafts. It is advantageous to use lithium niobate as a substrate material because of its linear temperature response and its high electro-mechanical coupling efficiency. With this material, however, the sensitivities of temperature and torque measurement are strongly different: a small change in temperature of only a few Kelvin will cause a sensor signal of the same amount as the nominal torque of a typical shaft. It is experimentally demonstrated that, despite the strong temperature sensitivity of the sensors, exact measurements of both torque and temperature can be accomplished over a wide temperature range from 0/spl deg/C to more than 70/spl deg/C, while the resolution of torque measurement is well below 1%. Deviations from linearity are small, so that a third order polynomial in temperature and torque is sufficient to describe the sensor response characteristics.

Coded 24 GHz Doppler radar sensors: a new approach to high-precision vehicle position and ground-speed sensing in railway and automobile applications

Coded 24 GHz Doppler sensors have been realized to perform high-precision non-contact vehicle position and speed measurements. Encoding the radar signal with a spread-spectrum code is the key to a significantly enhanced sensitivity combined with a range selectivity of the sensor. The novel system concept establishes a high-performance low-cost vehicle Doppler radar system with very high measurement accuracy suitable for automotive and railway applications.

Circuit arrangement of an ultrasonic-presence motion detector, particularly for a non-contact control of a water faucet

A circuit arrangement is disclosed which is suitable for ultrasonic-presence motion detection in which an ultrasonic transducer is provided as a transmitter and an ultrasonic transducer is provided as a receiver. An oscillator produces an ac voltage for the transmitting transducer, a gate circuit is provided in order to chronologically control the feeding of wave forms of the oscillator to the transmitting transducer, and a receiver circuit is provided which is connected to a receiving transducer and which obtains a received signal from the receiving transducer. An evaluation circuit is also provided. The receiver circuit has a phase discriminator in order to recognize the value of a phase displacement between the ac voltage of the oscillator and the respective received signal. An electronic storage circuit is connected to the output side of the phase discriminator and stores the output signal of the phase discriminator at predetermined periodically recurring time points which are determined by read-out pulse signals at the respective time points. The evaluation circuit comprises a comparator circuit in order to compare the individual or several consecutive stored values of the electronic storage circuit. The comparator circuit comprises a threshold function so that an output signal of the circuit arrangement is produced when the individual stored values or the mean values of a number of consecutive stored values differ from one another by more than a prescribed value. The output signal indicates the motion-presence phenomenon.

An ultrasonic flow meter for industrial applications using a helical sound path

A new ultrasonic measuring tube principle is presented which is usable for a wide range of tube diameters. The measuring device consists of a square tube in which two transducers and two special reflectors me mounted. In addition to these special reflectors, three wall reflections are used to form a helical sound path which integrates the flow independently from the fluid flow profile. The fluid velocity is derived from the difference in travel time between up and down stream travelling wave packets. In order to gain a measurement accuracy (linearity) of /spl plusmn/1% in a velocity range of 1:100, aspects of body sound, reflectional and zero flow effects must be taken into account. The progress gained by the new measuring principle is discussed on the basis of simulation and experimental investigations. Results are presented for different temperatures and over a wide range of flow velocities. The potential applications comprise flow measurement of liquids in the industry as well as heat metering in hot water supply.

Simulation of Acoustic Wave Propagation Within Flowing Media Using Simplified Boundary Element Techniques

The development of a novel ultrasonic gas meter1 for household applications demonstrated that ultrasound technique can be a very precise and cost effective method for flow meters. Fig. 1 shows the basic principle of an ultrasound meter based on the delay time measurement principle. The time of flight between the two transducers positioned along the flow channel is influenced by the mean flow along the measurement path. The mean flow rate can be calculated as

Direction-sensitive ultrasonic distance sensor using multimode stimulation of a single transducer

A novel ultrasonic sensor is presented which has the ability to determine the angle of incidence of sound waves by evaluating simultaneously different vibration modes of a single transducer. Since signals from the main lobe and sidelobes are discernible, side reflections can be identified and suppressed. Combining angle and distance measurement allows a detailed characterization of object scenes. The signal evaluation is performed by an adaptive algorithm incorporating Wiener filtering to improve the angular and axial resolution. The principle of the sensor is described and results for different object scenes are presented. Investigations on level measurements in silos proved the practical applicability of the method.

Broad beam ultrasonic transducer

Disclosed is a broad beam ultrasonic transducer of sandwich construction, having piezoceramic laminae (2), fitted with electrodes, and plates/films (3, 13) in the shape of a parallelepiped with a width (B) to length (L) ratio of 0.42 and in which the relative thicknesses of the piezoceramic laminae and the plates/films are chosen such that one side surface of the parallelepiped undergoes an in-phase oscillation behavior.

Weg- und Winkelsensoren

Weg- und Winkelaufnehmer werden uberall dort benotigt wo veranderliche Positionen, (Abstande, Langen oder Winkel) erfasst werden mussen, um entweder als reiner Messwert ausgegeben zu werden oder in einem Regelkreis zumeist die Regelgrose als Messwert zur Verfugung zu stellen. Grundsatzlich unterscheidet man zwischen beruhrenden (tastenden) und beruhrungslosen Aufnehmern. Zu den beruhrenden Sensoren zahlen dabei alle Aufnehmer, die ein spezielles Messobjekt als Weg- oder Winkelvermittler benotigen, das wahrend der Messung fest mit dem eigentlichen Messobjekt verbunden ist. Diese Bezeichnung gilt auch dann, wenn die eigentliche Messung gegen das vermittelnde Objekt im Endeffekt beruhrungslos erfolgt. Beruhrungslose Weg- und Winkelaufnehmer konnen ohne einen solchen Vermittler direkt gegen das zu vermessende Objekt messen.