Ch.S. Roumenin

Magnetic sensors continue to advance towards perfection

This work gives an up-to-date review of the new trends of solid-state magnetosensors such as orthogonal and parallel-field Hall devices, bipolar magnetotransistors (BMTs) and related transducers, multisensors for magnetic field, temperature and light, vector and gradient magnetometers, etc. Intense research aimed at the implementation of biomagnetosensors has been proposed.

Bipolar magnetotransistor sensors. An invited review

Abstract This comprehensive review of bipolar magnetotransistor (BMT) sensors is an attempt to consider from a general point of view the fundamental physical principles that determine magnetotransistor (MT) action, depending on the specific design and operating conditions. Some recently established properties of these sensors have likewise been included, e.g., the filament magnetosensitivity effect, electric control of the sign of the magnetosensitivity, etc. The principal connection of BMT sensors with Hall-effect devices has been established. The most important functional sensors, such as integrated vector transducers and multisensors, have been discussed. A comparison has been made of the magnetotransistor figures of merit.

Parallel-field Hall microsensors: an overview

Abstract This comprehensive overview of parallel-field or conformally transformed Hall microsensors is the first attempt to systematize their properties, operation and application. The planar location of their input and output contacts and their activation by a magnetic field parallel to the plane of the chip make these transducers especially promising for use in two- and three-dimensional magnetometers. The functional connection of the parallel-field Hall devices with bipolar lateral magnetotransistors has also been discussed.

Occupancy grids building by sonar and mobile robot

In this paper, a modified method for occupancy grid map building by a moving mobile robot and a scanning ultrasonic range-finder is proposed. The map building process consists of two phases: (1) gleaning of information from environment, and (2) sonar data processing. For sonar data processing the proposed modified method combines: (1) statistical approach for probability sonar model building; and (2) application of fuzzy logic theory for sonar data fusion. It is experimentally shown that, in some applications, the proposed modified method has advantages over other well-known methods.

Comparison of noise properties of different magnetic-field semiconductor integrated sensors

Abstract The noise properties of different silicon integrated magnetic-field sensors are presented, namely for the new gated silicon-on-sapphire micromagnetodiode, the lateral bipolar magnetotransistor, the MOS-Hall sensor and the MOS magnetotransistor (MAGFET). The noise sources are identified for each device and the relevant parameters are discussed. The corresponding limits in the detection of a magnetic field are also calculated. From the fact that they are all within flthe 0.1 to 10 μT range for sensors based on different principles, and give very different sensitivities, we suggest that this limit is more or less a characteristic of the semiconductor material (related to its physical parameters).

2D magnetodiode sensors based on SOS technology

Abstract A novel integrated device capable of measuring simultaneously the two in-plane components B x and B y of the magnetic-field vector is presented. The sensor is based on the magnetodiode principle and is fabricated by a silicon-on-sapphire (SOS) technology. This transducer consists of two one-dimensional differential (n + -n-p + -n-n + ) micromagnetodiodes positioned at an angle of 90° with a common central p + -n junction. Linear and odd output signals from the two channels in the −0.1 T ≤ B ≤ + 0.1 T magnetic-field range at T = 20 °C are obtained. No cross-sensitivity is observed experimentally. The differential approach suggested overcomes the non-linearity of the output characteristic and the strong temperature dependence on the output signal in bipolar SOS magnetosensitive devices.

Optimized emitter-injection modulation magnetotransistor

Abstract The magnetic-field sensitivity of a novel lateral p-n-p magnetotransistor with a double base contact is investigated experimentally. At low collector current levels, its magnetosensitivity increases exponentially by one to two orders of magnitude due to the emitter-injection modulation, caused by the Hall voltage, created in the base region. By selection of appropriate operating conditions and optimized positioning of the collector, the normally nonlinear output characteristic of the magnetotransistor is linearized. Based on this, a dual-collector differential version with linear output is developed.

Optimized parallel-field magnetotransistor sensor

Abstract A new phenomenon has been experimentally observed in planar drift- aided bipolar magnetotransistors. It consists in the electric control of the magnetosensitivity when the external magnetic field is applied parallel to the chip surface. A model is suggested, making use of the non-linear shape of the trajectory of the injected carriers, their non-uniform distribution on the cross-section of the structure and the deflection mechanism. This model allowed an optimized parallel-field bipolar sensor to be developed. The experiment shows that the device magnetosensitivity is now several times higher and reaches 12%/T.

Functional multisensor for magnetic field and temperature measurements

Abstract New linear multisensors built on a functional principle and designed for the simultaneous and independent measurements of magnetic field and temperature have been investigated. These transducers consist of bipolar differential magnetotransistors where the emitter-base bias is a linear thermometric signal, which under certain practical conditions does not depend on the value and direction of the external magnetic field. This peculiarity has also been used to reduce the temperature dependence of the magnetosensitivity over a wide temperature range. The conclusions corroborate the experimental data obtained for p + np + lateral dual-collector magneto-transistors. A maximum error of thermocompensation of magnetosensitivity of ∼2% has been attained in the range 0 ⩽ T ⩽ 80 °C, which is a very promising result.

Magnetotransistor sensors with amperometric output

Abstract A new operating principle of bipolar magnetotransistors (BMTs) is suggested and investigated experimentally. It is achieved without reverse biasing of the collector junctions and by using the current between the two ‘floating’ collectors as an information signal. The output current is a linear and odd function of the magnetic field. The advantages of the amperometric mode of operation dramatically change our concept of BMT as a transducing device.