Margarita Puentes

Metamaterial Inspired Microwave Sensors

Cheap and ubiquitous sensor systems will shape the coming decades. There is an emerging class of small high-performance electronic devices such as mobile phones, electronic toys, home appliances, monitoring and control systems in industrial facilities, and medical diagnosis systems, which are or will be equipped with pill box sized microprocessors or computers as well as sensors. These “smart sensors” with limited power and processing capabilities are often wirelessly interconnected. An assembly of many of them spread throughout the physical world will form sensor networks able to identify, localize, and monitor physical, environmental, and industrial processes, biological and health conditions, goods, vehicles, factories, stores, or even people.

Sensor array based on split ring resonators for analysis of organic tissues

A sensor array concept has been developed using microstrip-line-excited split ring resonators (SRR). With the proposed structure it is possible to spatially resolve the dielectric properties of a Material Under Test (MUT). The split rings are designed to have different resonant frequencies and are decoupled from each other to allow a spatial distribution where a frequency shift of one individual resonant peak will indicate the dielectric properties of the MUT and its location within the array. Several prototype sensors have been realized and tested with different MUT such as dielectric bricks and pig lung tissue to prove the concept.

Frequency Multiplexed 2-Dimensional Sensor Array Based on Split-Ring Resonators for Organic Tissue Analysis

A frequency multiplexed 2-dimensional sensor array was developed using microstrip-line-excited split-ring resonators (SRRs). With the proposed structures, it is possible to spatially resolve the relative changes of the dielectric properties of a Material Under Test (MUT) in one and two dimensions. The SRRs are designed to have different resonant frequencies and are decoupled from each other. With these design characteristics, it is possible to track changes on the resonant frequency of individual SRR that will indicate the dielectric properties of the MUT around the ring and therefore its location within the array. The number of pixels of the dielectric image corresponds to the number of SRRs within the sensor. Several prototype sensors have been realized and tested with different MUT such as dielectric bricks, animal tissue and phantoms of human tissue to prove the concept.

Artificial transmission lines for high sensitive microwave sensors

Two common and two new unit cells for artificial lines made of four reactive elements are studied concerning their sensitivity to capacitive changes and their applicability as capacitive sensors. It is shown that selection of the unit cell is very important and can highly influence the sensitivity. The shown principle is very powerful and can be scaled up to THz frequencies, only limited by available fabrication technology. A built planar differential microwave sensor based on artificial lines working at 2.3 GHz is presented. It features a simple output power evaluation instead of a classic but more complicated phase difference measurement. With power variation of up to 60 dB in dependence of small environmental dielectric changes it shows a very high sensitivity and dynamic range. Functional layer coatings can be applied easily due to its planarity and open wide application areas for biomedical sensing.

Multi-resonant perturbation method for capacitive sensing with composite right/left-handed transmission lines

The possibility to use the left-handed capacitances of a composite right/left-handed (CRLH) transmission line for a capacitive sensor array is demonstrated. The capacitances values are extracted with the presented algorithm that is based on a multi-resonant perturbation technique. The CRLH line structure was chosen since its physical implementation is much better suited to a capacitive sensing transmission line than a right-handed (RH) one. In contrast to other techniques like time domain reflectometry single cell spatial resolution can be achieved with moderate bandwidth demand. Presented numerical and experimental results prove the concept.

Capacitive level monitoring of layered fillings in vessels using composite right/left-handed transmission lines

This paper presents a concept for level monitoring of layered fillings in vessels with partially or completely unknown properties of the filling materials. A key sensor component is a composite right/left-handed transmission line resonator. Based on this element in combination with the multi resonant cavity perturbation theory an algorithm for the sensor signal processing is derived for the extraction of material properties and filling levels. The presented concept is verified with full wave electromagnetic simulations and experiments that had been carried out with a realized demonstrator.

Dual mode microwave tool for dielectric analysis and thermal ablation treatment of organic tissue

A dual mode tool design to analyze organic tissue and locally perform thermal ablation treatment is presented. The tool is made of an array of split-ring resonators. It can operate on a sensing mode to track the relative dielectric changes from the organic tissue and on a treatment mode to perform thermal ablation at different input powers. The measurements were done with phantoms of human tissue. The tool is able to focus a hot spot of approximately 0.2mm with a temperature of 109 °C at an input power of 10W.

Dual mode sensor for belt conveyor systems based on planar metamaterials

A new sensor concept has been developed using a metamaterial transmission line with two different operation modes for the simultaneous detection of material permittivity and position. In the first mode the sensor is used as a resonator and the permittivity is detected accurately and with a moderate cost. On the second mode the sensor is used as a transmission line and the spatial material distribution is detected using time domain reflectometry techniques. A prototype sensor has been realized and tested in a dedicated measurement setup. The areas of application of these types of sensors are material monitoring during transportation in conveyor belts for several industrial processes.

Microwave Mass Flow Meter for Industrial Applications based on a Lefthanded Transmission Line Resonator

A particulates mass flow meter has been developed using a composite right/left-handed transmission line resonator. The presented sensor principle promises the possibility to design precise particulate solids mass flow meter with moderate costs. The autocorrelation function is applied to the CRLH-resonator in order to detect the velocity information and the material density from a single measurement. The areas of application of these sensors are gas/solids, gas/liquid and liquid/solids flows in various industrial applications.

Microwave mass flow meter for pneumatic conveyed particulate solids

A particulates mass flow meter has been developed using a composite right/left-handed transmission line resonator. The presented sensor principle promises the possibility to design precise particulate solids mass flow meter with moderate costs. The Spatial Filter Velocimetry is applied to the sensor in order to detect the velocity information. The simultaneous detection of the velocity and the solids/air concentration from a single measurement, ensure a true mass flow detector. The detector offers good prospects for industrial applications with various scenarios of gas/solids, gas/liquid and liquid/solids flows.