Timo Varpula

Antenna Effective Aperture Measurement With Backscattering Modulation

A scattering measurement method for antenna characterization is described. The antenna backscattering is modulated by an oscillator circuit. The modulation begins, when a known RF power is transferred to the oscillator circuit from the antenna. This enables the measurement of the effective aperture of the antenna, from which the antenna bandwidth and radiation pattern are obtained. A theory for antenna aperture measurement is developed using a simple circuit model for the antenna-oscillator system. A dipole and a PIFA with a reactive input impedance at the application frequency were measured. The antenna aperture was measured to an accuracy of 9%, and the measurements complied with simulated and measured references. The method provides simple and accurate bandwidth and radiation pattern measurements with the reactive load the antenna is designed to work with.

Road-Condition Recognition Using 24-GHz Automotive Radar

This paper studies 24-GHz automotive radar technology for detecting low-friction spots caused by water, ice, or snow on asphalt. The backscattering properties of asphalt in different conditions are studied in both laboratory and field experiments. In addition, the effect of water on the backscattering properties of asphalt is studied with a surface scattering model. The results suggest that low-friction spots could be detected with a radar by comparing backscattered signals at different polarizations. The requirements for the radar are considered, and a 24-GHz radar for road-condition recognition is found to be feasible.

Technical Solutions for Automotive Intermodulation Radar for Detecting Vulnerable Road Users

Technical solutions for automotive intermodulation radar for detecting vulnerable road users

Inductive noise thermometer: Practical realization

A new concept, called inductive noise thermometer, for measuring temperature of electrically conductive materials without any physical contact was realized in practice. In the method a low‐loss coil is placed close to the electrically conductive material. The increase in the noise voltage of the coil is related to the temperature of the material. Results from laboratory experiments on steel up to temperatures of 1300 K showed an agreement with conventional thermocouple recordings within an uncertainty of 1%. The thermometer built was also tested on a continuous casting machine of a steel mill. The preliminary experimental results were encouraging although at times external rf disturbances disrupted the measurement.

Inductive noise thermometer: Theoretical aspects

We describe a new noncontacting method for measuring the temperature of electrically conducting objects by sensing the magnetic field noise. When a high‐Q antenna is placed close to a conductive material, e.g., a hot metal plate, the effective noise temperature of the antenna becomes proportional to the temperature of the material. Contrary to the conventional noise thermometer in which a resistor is embedded in the material, the method requires neither galvanic nor thermal contact. If the antenna impedance at different frequencies is known, the temperature of the object can be calculated from the total voltage noise of the antenna. We show, however, that for high‐Q antennae the knowledge of the impedance at resonance is adequate to determine the unknown temperature. Consequently, the temperature of moving objects can be measured via synchronous monitoring of the total noise of the antenna and its impedance at resonance. Since only electrically conductive objects create magnetic field noise, the method is...

A tyre sensor system with electronics for data transmission and power supply

The Apollo research project is aimed at developing a prototype of an intelligent tyre. The overall goals are to increase traffic safety and enable improvements in vehicle dynamics control, advanced driver assistance systems and services for external users by providing data on the tyre and the local tyre-to-road contact.

Microwave Fibre Orientation Sensor

A new sensor based on a microwave resonator for measuring the fibre orientation in sheets was developed. The device is non-contacting and is suitable for measurements of moving web in paper and board machines. It can also be applied to measure the molecular orientation of plastic films. With this novel method, the fibre orientation can be measured without rotating the sample and the sensor with respect to each other The measurement results of the device were compared to the results obtained with ultrasonic tensile stiffness orientation on paper samples (TSO). TSO gave identical orientation angles but the orientation ratios were different in some samples. This is because TSO is also sensitive to strains in fibre, whereas the microwave method reflects the true geometric fibre orientation. The uncertainty of the orientation angle measurement with the microwave device is less than 0.4 degrees.