Arduino biological sensor with bluetooth conection to android app

En el presente Trabajo Fin de Grado se expone una aplicación para terminales móviles que permite la adquisición y representación, entre otras funcionalidades, del electrocardiograma y el electromiograma del usuario. La adquisición de los datos biométricos está realizada mediante una arquitectura Arduino UNO Rev. 3 extendida con el sistema e-Health Sensor Shield V2.0. La comunicación entre el bloque de adquisición de datos y la aplicación móvil se realiza mediante el protocolo Bluetooth gracias a la extensión para Arduino Communication XBee Shield con el Bluetooth Module PRO. La aplicación móvil ha sido desarrollada sobre Android a través del entorno de desarrollo Android Studio. Dicha aplicación permite la representación gráfica de los datos obtenidos, así como su almacenamiento para su posterior visualización. Por otro lado, la aplicación también incorpora dos pequeños experimentos. El primero de ellos, consiste en el análisis de la modificación del ritmo cardiaco en función del tipo de música escuchada. El segundo,en el análisis de la intensidad media y duración de los impulso musculares

Application of split ring resonator (SRR) loaded transmission lines to the design of angular displacement and velocity sensors for space applications

The accurate measurement of the angular displacement and velocity of reaction wheels is necessary for attitude (orientation) control in space vehicles (satellites). In this paper, microwave, contactless, and low-cost (as compared to optical encoders) sensors useful for that purpose are analyzed in detail. The sensor consists of a rotor and a stator. The rotor is a disk (or a circular crown) of dielectric material, where one or several arrays of equidistant single-loop split ring resonators (SRRs) are etched along its edge, forming circular chains of hundreds of SRRs. The stator is a coplanar waveguide (CPW) also loaded with pairs of single-loop SRRs (etched in the back substrate side), with the centers located in the slot region. The sensing principle is based on the amplitude modulation of a harmonic (single-tone continuous wave) feeding signal, achieved when the chains of the rotor are displaced over the SRR pairs of the stator. Both sensor elements (rotor and stator) must be parallel oriented, with the SRR pairs of the CPW in close proximity to the SRR chains of the rotor (and rotated 180°), in order to favor their coupling. By this means, the transmission coefficient of the CPW is varied by the circular motion of the rotor, and significant amplitude modulation of the feeding signal is achieved. From the envelope function, the angular velocity can be accurately determined. With the proposed sensors, instantaneous and practically unlimited rotation speeds can be measured

High-density microwave encoders for motion control and near-field chipless-RFID

A novel microwave system for measuring linear displacements and velocities with sub-millimeter resolution and for the implementation of near-field chipless radiofrequency identification (chipless-RFID) systems with very high data capacity is presented. The system is based on a reader, consisting of a half-wavelength straight resonator coupled (through capacitor gaps) to a pair of access lines, and a microwave encoder, in relative motion to the reader and consisting of a linear chain of strips orthogonally oriented to the chain axis. By displacing the encoder over the half-wavelength resonator of the reader, with the encoder strips parallel oriented to the reader axis, the relative velocity and position between the encoder and the reader can be inferred. For that purpose, the reader is fed by a harmonic signal tuned to the resonance frequency that results when an encoder strip is perfectly aligned with the reader. The encoder motion amplitude modulates the feeding signal at the output port, and both the position and the velocity are measured from the peaks, or dips, of the resulting envelope function. Moreover, by making certain strips inoperative, the system can be used for coding purposes. Due to the small period of the encoder (0.6 mm), a high per-unit-length data density in these near-field chipless-RFID tags (i.e., 16.66 bits/cm) is achieved. To illustrate the functionality and potential of the approach, 100-bit chipless-RFID tags with various ID codes are implemented and rea

Chipless-RFID : a review and recent developments

In this paper, a review of the state-of-the-art chipless radiofrequency identification (RFID) technology is carried out. This recent technology may provide low cost tags as long as these tags are not equipped with application specific integrated circuits (ASICs). Nevertheless, chipless-RFID presents a series of technological challenges that have been addressed by different research groups in the last decade. One of these challenges is to increase the data storage capacity of tags, in order to be competitive with optical barcodes, or even with chip-based RFID tags. Thus, the main aim of this paper is to properly clarify the advantages and disadvantages of chipless-RFID technology. Moreover, since the coding information is an important aspect in such technology, the di_erent coding techniques, as well as the main figures of merit used to compare di_erent chipless-RFID tags, will be analyzed

Microwave encoders for chipless RFID and angular velocity sensors based on S-shaped split ring resonators

In this paper, it is demonstrated that a chain of S-shaped split ring resonators (S-SRRs) etched on a dielectric substrate can modulate the amplitude of a carrier signal injected to a transmission line (a coplanar waveguide (CPW). To this end, the S-SRR chain must be transversally displaced above the CPW, in close proximity to it. By this means, the transmission coefficient of the line is modulated by the time-varying electromagnetic (inductive) coupling between the line and the S-SRRs of the chain, related to their relative motion. Based on this principle, two different applications can be envisaged: 1) angular velocity sensors and 2) near-field chipless radiofrequency identification (chipless-RFID) tags. In the former application, the S-SRR chain is circularly shaped and the S-SRRs are distributed uniformly along the perimeter of the rotor, at equidistant positions. By this means, the amplitude-modulated signal generated by rotor motion exhibits envelope peaks, whose distance is related to the angular velocity of the rotor. In the use of S-SRRs as microwave encoders for chipless RFID tags, not all the S-SRRs of the chain are present. Their presence or absence at the predefined (equidistant) positions is related to the logic state "1" or "0." Tag reading is sequential, and it is achieved through tag motion (at constant velocity) above the reader, a CPW transmission line fed by a carrier signal. The ID code is contained in the envelope function of the resulting amplitude modulated signal, which can be obtained by means of an envelope detector. With the proposed approach, a high number of pulses in angular velocity sensors can be achieved (with direct impact on angle resolution and sensitivity to changes in instantaneous rotation speed). Moreover, chipless-RFID tags with unprecedented number of bits can be obtained. The proposed angular velocity sensors can be useful in space environments, whereas the chipless-RFID systems based on the proposed tags are useful in applications where reading range can be sacrificed in favor of high data capacity (large number of bits), e.g., security and authentication

Recent advances in the modeling of transmission lines loaded with split ring resonators (SRRs)

This paper reviews the recent advances in the modeling of transmission lines loaded with split ring resonators (SRRs). It is well known that these artificial lines can exhibit a negative effective permeability in a narrow band above the SRR fundamental resonance, providing stopband functionality. By introducing shunt inductive elements to the line, the stopband can be switched to a pass band with left-handed (LH) wave propagation. For the design of microwave circuits based on these artificial lines, accurate circuit models are necessary. The former circuit model of SRR-loaded lines was presented more than one decade ago and is valid under restrictive conditions. This paper presents the progress achieved in the modeling of these artificial lines during the last years. The analysis, restricted to coplanar waveguide (CPW) transmission lines loaded only with SRRs (negative permeability transmission lines), includes the effects of SRR orientation, the coupling between adjacent resonators, and the coupling between the two SRRs constituting the unit cell. The proposed circuit models are validated through electromagnetic simulation and experimental data. It is also pointed out that the analysis can be easily extended to negative permittivity transmission lines based on complementary split ring resonators (CSRRs)

Miniature Microwave Notch Filters and Comparators Based on Transmission Lines Loaded with Stepped Impedance Resonators (SIRs)

In this paper, different configurations of transmission lines loaded with stepped impedance resonators (SIRs) are reviewed. This includes microstrip lines loaded with pairs of SIRs, and coplanar waveguides (CPW) loaded with multi-section SIRs. Due to the high electric coupling between the line and the resonant elements, the structures are electrically small, i.e., dimensions are small as compared to the wavelength at the fundamental resonance. The circuit models describing these structures are discussed and validated, and the potential applications as notch filters and comparators are highlighted

Analysis of transmission lines loaded with pairs of coupled resonant elements and application to sensors

This paper is focused on the analysis of transmission lines loaded with pairs of magnetically coupled resonators. We have considered two different structures: (i) a microstrip line loaded with pairs of stepped impedance resonators (SIRs), and (ii) a coplanar waveguide (CPW) transmission line loaded with pairs of split ring resonators (SRRs). In both cases, the line exhibits a single resonance frequency (transmission zero) if the resonators are identical (symmetric structure with regard to the line axis), and this resonance is different to the one of the line loaded with a single resonator due to inter-resonator coupling. If the structures are asymmetric, inter-resonator coupling enhances the distance between the two split resonance frequencies that arise. In spite that the considered lines and loading resonators are very different and are described by different lumped element equivalent circuit models, the phenomenology associated to the effects of coupling is exactly the same, and the resonance frequencies are given by identical expressions. The reported lumped element circuit models of both structures are validated by comparing the circuit simulations with extracted parameters with both electromagnetic simulations and experimental data. These structures can be useful for the implementation of microwave sensors based on symmetry properties

Symmetry-Related Electromagnetic Properties of Resonator-Loaded Transmission Lines and Applications

This paper reviews the recent progress in the analysis and applications of the symmetry-related electromagnetic properties of transmission lines loaded with symmetric configurations of resonant elements. It will be shown that the transmission characteristics of these reactively loaded lines can be controlled by the relative orientation between the line and the resonant elements. Two main types of loaded lines are considered: (i) resonance-based structures; and (ii) frequency-splitting structures. In resonance-based transmission lines, a line is loaded with a single resonant (and symmetric) element. For a perfectly symmetric structure, the line is transparent if the line and resonator exhibit symmetry planes of different electromagnetic nature (electric or magnetic wall), whereas the line exhibits a notch (resonance) in the transmission coefficient if the symmetry planes behave as either electric or magnetic walls (symmetric configuration), or if symmetry is broken. In frequency-splitting lines, paired resonators are typically loaded to the transmission line; the structure exhibits a single notch for the symmetric configuration, whereas generally two split notches appear when symmetry is disrupted. Applications of these structures include microwave sensors (e.g., contactless sensors of spatial variables), selective mode suppressors (of application in common-mode suppressed differential lines, for instance) and spectral signature barcodes, among others

Modeling metamaterial transmission lines loaded with pairs of coupled split-ring resonators

A lumped-element equivalent circuit model of the unit cell of metamaterial transmission lines loaded with pairs of coupled split-ring resonators (SRRs) is presented. It is assumed that the dominant coupling mechanism between the SRRs forming the pair is magnetic, and that the distance between SRRs of adjacent cells is high enough to neglect such additional inter-resonator coupling. SRRs are oriented with their symmetry plane orthogonal to the line axis. Under these conditions, the line-to-SRR coupling is also magnetic, the electric coupling being negligible. The presented model accounts for the rupture of symmetry that can be caused, for instance, by asymmetric dielectric loading of the SRRs. Thus, the analysis is carried out on a general model where the SRRs of the pair have different inductance and capacitance. Then, different cases are studied, in particular a line with identical SRRs, and a line with different SRRs, but with the same resonance frequency. It is shown that coupling between SRRs tends to far or split the resonance frequencies of the loaded lines (transmission zeros), except for the symmetric case, where only one resonance (different to the one of uncoupled SRRs) appears. The model is validated by comparing circuit simulations using extracted parameters with electromagnetic simulations and experimental data