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  • A figure-of-merit for pattern reconfigurable antennas

     Rodrigo Lopez, Daniel; Romeu Robert, Jordi; Capdevila Cascante, Santiago; Jofre Roca, Luis
    IEEE transactions on antennas and propagation
    Date of publication: 2013-03
    Journal article

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  • A new class of antenna array with a reconfigurable element factor

     Li, Zhouyuan; Rodrigo Lopez, Daniel; Jofre Roca, Luis; Cetiner, Bedri Artug
    IEEE transactions on antennas and propagation
    Date of publication: 2013-04
    Journal article

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  • Design guidelines for a terahertz silicon micro-lens antenna

     Alonso Del Pino, Maria; Llombart, Núria; Chattopadhyay, G.; Lee, Craig; Jung Kubiak, Cecile; Jofre Roca, Luis; Mehdi, Imran
    IEEE antennas and wireless propagation letters
    Date of publication: 2013-01-15
    Journal article

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    A silicon lens antenna suited for future integrated terahertz arrays has been proposed recently. The antenna consists of an extended hemispherical silicon lens fed by a leaky-wave waveguide feed. The primary advantage is that the antenna is compatible with silicon micro-fabrication techniques as only a small sector of the lens is actually used. Moreover, it can be easily integrated with other silicon micromachined front-end components. In this letter, the design and optimization details of such a micro-lens antenna is presented. The design is validated with a set of measurements at 550 GHz from a prototype that has been fabricated using laser micro-fabrication.

  • Antenna input impedance measurement using multi-load MST

     Romeu Robert, Jordi; Capdevila Cascante, Santiago; Bolomey, Jean Charles; Jofre Roca, Luis
    International Workshop on Antenna Technology
    Presentation's date: 2013-03
    Presentation of work at congresses

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    This paper presents the practical use of modulated scatterer technique (MST) for the measurement of the antenna input impedance using a multi-load automatic switching device, and it also includes the analysis of the measurement error as a function of the selected loads in the MST circuitry

  • Characterization of pharmaceuticals using Terahertz Time Domain spectral-tomography

     Nova Lavado, Enrique; Roqueta Crusats, Gemma; Romeu Robert, Jordi; Jofre Roca, Luis
    European Conference on Antennas and Propagation
    Presentation's date: 2013
    Presentation of work at congresses

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    In this paper a Terahertz Time-Domain measurement system has been used to perform Tomographic imaging of pharmaceutical compounds with coating. Measurements on paracetamol and ibuprofene samples are done both in transmission and reflection geometries and their capabilities are compared. Results of the contrast reconstructions provide information of the relative permittivity of the pharmaceutical compounds. The interfaces between materials with different permittivities are detected, thus allowing characterization of different layers of the compound.

    In this paper a Terahertz T ime-Domain measurement system has been used to perform Tomographic imaging of pharmaceutical compounds with coating. Measurements on paracetamol and ibuprofene samples are done both in transmission and reflection geometries and their capabilities are compared. Results of the contrast reconstructions provide information of the relative permittivity of the pharmaceutical compounds. T he interfaces between materials with different permittivities are detected, thus allowing characterization of different layers of the compound.

  • Design of a dielectric flat lens antenna for 60 GHz WPAN applications

     Imbert Villa, Marc; Romeu Robert, Jordi; Jofre Roca, Luis
    IEEE International Symposium on Antennas and Propagation
    Presentation's date: 2013-07
    Presentation of work at congresses

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    In this paper we present the design of a dielectric flat lens antenna to operate in the 60 GHz band for WPAN applications. In order to overcome the specific atmospheric attenuation, which characterizes the propagation in the 60 GHz band, high directive antennas are required. Moreover, due to high user random mobility in indoor environments, beam-steerable antennas are also needed. For these reasons, we propose a design based on a dielectric flat lens antenna with scanning capabilities from -30° to +30° with around 20 dB of gain in the whole entire band of interest (57 to 66 GHz), and up to ±60° of beam-steering capabilities with around 15 dB of gain. The dielectric flat lens also leads to low-profile antenna configuration, easy to manufacture and low-cost, in order to integrate the design together with a commercial RF CMOS chip.

  • A frequency reconfigurable cell for beam-scanning reflectarrays

     Rodrigo Lopez, Daniel; Jofre Roca, Luis; Perruisseau Carrier, Julien
    IEEE International Symposium on Antennas and Propagation
    Presentation's date: 2013-07
    Presentation of work at congresses

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    Reflectarray antennas are excellent candidates for beam-scanning applications thanks to their low loss, light and quasi-planar structure and ease of electronic control. However, reflectarray antennas suffer from narrower bandwidths than phased arrays and reflector solutions. In this context we present a frequency-reconfigurable cell for beam-scanning reflectarrays, as a solution for applications that operate over a large frequency range but that require a narrower instantaneous bandwidth. The presented cell requires only two switches and one varactor to provide a reflection coefficient with continuously tunable phase over a 270° range which can be shifted over a 40% frequency range.

  • RF MEMS reconfigurable two-band antenna

     Zohur, Abdul; Mopidevi, Hema Swaroop; Rodrigo Lopez, Daniel; Unlu, M.; Jofre Roca, Luis; Cetiner, Bedri Artug
    IEEE antennas and wireless propagation letters
    Date of publication: 2013-01-09
    Journal article

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  • Radiometric and spatial resolution constraints in millimeter-mave close-range passive screener systems

     Nova Lavado, Enrique; Romeu Robert, Jordi; Torres Torres, Francisco; Pablos Hernandez, Miriam; Riera Salis, Jose Manuel; Broquetas Ibars, Antoni; Jofre Roca, Luis
    IEEE transactions on geoscience and remote sensing
    Date of publication: 2013-04
    Journal article

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    This paper presents a comparative study of the radiometric sensitivity and spatial resolution of three near-field (NF) passive screener systems: real aperture, 1-D synthetic aperture (SA), and 2-D SA radiometers are compared. The analytical expressions for the radiometric resolution, the number of required antennas, and the number of pixels in the image are derived taking into account the distortion produced by the NF geometry at nonboresight directions where the distortion is dominant. Based on the theoretical results, a performance comparison among the studied systems is carried out to show the advantages and drawbacks when using the radiometers in a close-range screening application. Moreover, the screener performance in a close-range environment is discussed from the results obtained in the aforementioned comparison.

  • Silicon micromachined lens antenna for THz integrated heterodyne arrays

     Llombart Juan, Nuria; Lee, Choonsup; Alonso Del Pino, Maria; Chattopadhyay, Goutam; Jung Kubiak, Cecile; Jofre Roca, Luis; Mehdi, Imran
    IEEE Transactions on Terahertz Science and Technology
    Date of publication: 2013-09
    Journal article

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    In this paper, we present the design, fabrication, and measurements of a lens THz antenna that can be fabricated using conventional photolithography and deep reactive etching processes. The antenna is composed of an extended hemispherical silicon lens and a leaky wave waveguide feed. Both elements are fabricated using silicon micromachining techniques, enabling the fabrication of future large antenna arrays with a parallel process. To show the concept, a first antenna prototype has been fabricated using this fabrication process. Measurements obtained at 550 GHz are presented.

  • Design of Isofrequency Reconfigurable Repeaters

     Diaz Tapia, Edgar
    Defense's date: 2013-10-28
    Department of Signal Theory and Communications, Universitat Politècnica de Catalunya
    Theses

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  • Terahertz Integrated Antenna Arrays for Imaging Applications

     Alonso Del Pino, Maria
    Defense's date: 2013-10-25
    Department of Signal Theory and Communications, Universitat Politècnica de Catalunya
    Theses

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  • Multi-antenna Multi-frequency Microwave Imaging Systems for Biomedical Applications

     Guardiola Garcia, Marta
    Defense's date: 2013-10-31
    Department of Signal Theory and Communications, Universitat Politècnica de Catalunya
    Theses

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  • Reconfigurable Pixel Antennas for Communications.  Open access

     Rodrigo Lopez, Daniel
    Defense's date: 2013-06-14
    Department of Signal Theory and Communications, Universitat Politècnica de Catalunya
    Theses

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    The explosive growth of wireless communications has brought new requirements in terms of compactness, mobility and multi-functionality that pushes antenna research. In this context, recon gurable antennas have gained a lot of attention due to their ability to adjust dynamically their frequency and radiation properties, providing multiple functionalities and being able to adapt themselves to a changing environment. A pixel antenna is a particular type of recon gurable antenna composed of a grid of metallic patches interconnected by RF-switches which can dynamically reshape its active surface. This capability provides pixel antennas with a recon guration level much higher than in other recon gurable architectures. Despite the outstanding recon guration capabilities of pixel antennas, there are important practical issues related to the performance-complexity balance that must be addressed before they can be implemented in commercial systems. This doctoral work focuses on the minimization of the pixel antenna complexity while maximizing its recon guration capabilities, contributing to the development of pixel antennas from a conceptual structure towards a practical recon gurable antenna architecture. First, the conceptualization of novel pixel geometries is addressed. It is shown that antenna complexity can be signi cantly reduced by using multiple-sized pixels. This multi-size technique allows to design pixel antennas with a number of switches one order of magnitude lower than in common pixel structures, while preserving high multiparameter recon gurability. A new conceptual architecture where the pixel surface acts as a parasitic layer is also proposed. The parasitic nature of the pixel layer leads to important advantages regarding the switch biasing and integration possibilities. Secondly, new pixel recon guration technologies are explored. After investigating the capabilities of semiconductors and RF-MEMS switches, micro uidic technology is proposed as a new technology to create and remove liquid metal pixels rather than interconnecting them. Thirdly, the full multi-parameter recon guration capabilities of pixel antennas is explored, which contrasts with the partial explorations available in the literature. The maximum achievable recon guration ranges (frequency range, beam-steering angular range and polarization modes) as well as the linkage between the di erent parameter under recon guration are studied. Finally, the performance of recon gurable antennas in beam-steering applications is analyzed. Figures-of-merit are derived to quantify radiation pattern recon gurability, enabling the evaluation of the performance of recon gurable antennas, pixel antennas and recon guration algorithms.

  • RFID Multiantenna Systems for Wireless Communications and Sensing  Open access

     Capdevila Cascante, Santiago
    Defense's date: 2013-02-15
    Department of Signal Theory and Communications, Universitat Politècnica de Catalunya
    Theses

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    Many scientific, industrial and medical applications require the measurement of different physical parameters in order to collect information about the spatially distributed status of some process. Very often this information needs to be collected remotely, either due to the spatial dispersion of the measurement points or due to their inaccessibility. A wireless embedded self-powered sensor may be a convenient solution to be placed at these inaccessible locations. This thesis is devoted to study the analytical relation governing the electromagnetic coupling between a reader and a embeddable self-powered sensor, based on radio frequency identification (RFID) technology, which is capable of wirelessly retrieving the status of physical parameters at a remote and inaccessible location. The physical parameter to be sensed may be the electromagnetic (EM) field existing at that location (primary measurement) or the indirect measurement of other parameters such as the temperature, humidity, etc. (secondary measurement). Given the simplicity of the RFID solution (highly embeddable properties, scavenging capabilities, penetration and radio coverage characteristics, etc.) the measurement can be done at a single location, or it can be extended to a set of measuring locations (an array or grid of sensors). The analytical relation is based on a reciprocity formulation studying the modulation of the scattered field by the embedded sensor in relation with the incident field, and allows to define a set of quality parameters of interest for the optimum design of the sensors. Particular attention is given to the scavenging circuitry as well as to the antenna design relevant to the sensing objective. In RFID tags, the existence of an RF harvesting section is an improvement with respect to conventional scattering field probes since it removes the need of DC biasing lines or optical fibers to modulate the sensor. However, this harvesting section introduces non-linearities in the response of the sensor, which requires a proper correction to use them as EM-field probes, although the characterization of the non-linearities of the RFID tag cannot be directly done using a conventional vector network analyzer (VNA), due to the requirements of an RFID protocol excitation. Due to this, this thesis proposes an alternative measurement approach that allows to characterize the different scattering states used for the modulation, in particular its non-linear behavior. In addittion, and taking this characterization as the starting point, this thesis proposes a new measurement setup for EM-field measurements based on the use of multiple tones to enlarge the available dynamic range, which is experimentally demonstrated in the measurement of a radiation pattern, as well as in imaging applications. The RFID-based sensor response is electromagnetically sensitive to the dielectric properties of its close environment. However, the governing formulation for the response of the probe mixes together a set of different contributions, the path-loss, the antenna impedance, the loads impedance, etc. As a consequence, it is not possible to isolate each contribution from the others using the information available with a conventional RFID sensor. This thesis mathematically proposes and experimentally develops a modification of the modulation scheme to introduce a new set of multi-load scattering states that increases the information available in the response and properly isolate each term. Moreover, this thesis goes a step forward and introduces a new scattering state of the probe sensitive to temperature variations that do not depend on the environment characteristics. This new configuration enables robust environmental sensing in addition to EM-field measurements, and sensing variations of the dielectric properties of the environment.

  • Radiometric and spatial resolution constraints in millimeter-wave close-range passive screener systems

     Nova Lavado, Enrique; Romeu Robert, Jordi; Torres Torres, Francisco; Pablos, M.; Riera, J.M.; Broquetas Ibars, Antoni; Jofre Roca, Luis
    IEEE transactions on geoscience and remote sensing
    Date of publication: 2013-04
    Journal article

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    This paper presents a comparative study of the radiometric sensitivity and spatial resolution of three near-field (NF) passive screener systems: real aperture, 1-D synthetic aperture (SA), and 2-D SA radiometers are compared. The analytical expressions for the radiometric resolution, the number of required antennas, and the number of pixels in the image are derived taking into account the distortion produced by the NF geometry at nonboresight directions where the distortion is dominant. Based on the theoretical results, a performance comparison among the studied systems is carried out to show the advantages and drawbacks when using the radiometers in a close-range screening application. Moreover, the screener performance in a close-range environment is discussed from the results obtained in the aforementioned comparison.

  • Enhancing RFID sensing capabilities: multi-load backscattering

     Capdevila Cascante, Santiago; Jofre Roca, Luis; Romeu Robert, Jordi; Bolomey, Jean Charles
    IEEE International Symposium on Antennas and Propagation
    Presentation's date: 2013-07
    Presentation of work at congresses

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    This conference paper presents some experimental results using the concept of an multi-loaded enhanced RFID tag capable of switching between different loads to fully determine the input impedance of the RFID tag antenna which can then be used for sensing applications.

  • 94 GHz cassegrain reflector antenna performance characterization

     Nova Lavado, Enrique; Rodrigo Lopez, Daniel; Romeu Robert, Jordi; Jofre Roca, Luis
    European Conference on Antennas and Propagation
    Presentation's date: 2012
    Presentation of work at congresses

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  • Interference rejection using frequency and pattern reconfigurable antennas

     Rodrigo Lopez, Daniel; Romeu Robert, Jordi; Jofre Roca, Luis
    IEEE International Symposium on Antennas and Propagation
    Presentation's date: 2012-07-13
    Presentation of work at congresses

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    Interference rejection by taking advantage of the radiation pattern diversity of a reconfigurable antenna is considered. It is proposed to use simultaneously frequency and radiation reconfiguration to extend interference rejection capabilities to large bandwidths. A small-size low-complexity pixel antenna is used to provide interference rejection capabilities over an octave bandwidth. An average signal-to-interference ratio of 24 dB is achieved and interference rejections above 15 dB are reliably provided over the whole frequency bandwidth and an angular range of 120o

  • MM-wave scattering measurements for imaging and channel characterization

     Toda, A.P.; de Flaviis, Franco; Jofre Roca, Luis; Romeu Robert, Jordi
    European Conference on Antennas and Propagation
    Presentation's date: 2012
    Presentation of work at congresses

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    In this paper, mm-wave band scattering measurements are performed and imaging reconstructions obtained using a 2-D Scatterer Mapping Technique based on a Multi-Frequency Bi-Focusing operator (MF-BF). The measured data matrix is also processed to obtain its eigenvalues and eigenvectors. A relation between the eigenvalues and the number of scatterers and the eigenvectors and the scatterers spatial localization is obtained.

    In this paper, mm-wave band scattering measurements are performed and imaging reconstructions obtained using a 2-D Scatterer Mapping Technique based on a Multi-Frequency Bi-Focusing operator (MF-BF). The measured data matrix is also processed to obtain its eigenvalues and eigenvectors. A relation between the eigenvalues and the number of scatterers and the eigenvectors and the scatterers spatial localization is obtained.

  • UWB Magnitude combined realistic breast model imaging capabilities

     Guardiola, Marta; Jofre Roca, Luis; Romeu Robert, Jordi
    IEEE International Symposium on Antennas and Propagation
    Presentation's date: 2012-07
    Presentation of work at congresses

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    Breast cancer is the leading cancer killer among women. Early stage detection has been recognized to be best solution to reduce mortality rates. A non-ionizing, economical screening system based on microwave imaging is being investigated, but it is still a long way towards clinical ready system. In this paper, the validation of UWB-MC tomographic algorithm is performed using realistic breast models.

  • Optical cross-correlation of millimeter wave signals applied to interferometric radiometry

     Nova, Enrique; Romeu Robert, Jordi; Torres Torres, Francisco; Broquetas Ibars, Antoni; Jofre Roca, Luis
    International Conference on Infrared, Millimeter, and Terahertz Waves
    Presentation's date: 2012-07
    Presentation of work at congresses

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    This paper presents a method to perform in the opti- cal domain the correlations required when processing millimeter wave interferometric radiometer signals. The main problem when addressing the design of an interferometric radiometer working at W-band resides on the distribution and correlation of large bandwidth signals acquired by each radiometer receiver. In order to avoid the necessity of baseband processing of signals with large relative bandwidths, the signals coming from the radiometric receivers are up-converted to the optical domain using LiNbO3 optical phase modulators. The modulated signals from each receiver pairs are added and and detected by a photodiode. The correlation is obtained from the resulting photocurrent.

  • Retina design for 100GHz MST imaging system

     Alonso, Maria; Garg, V.; Nova, Enrique; Abril, Jordi; Romeu Robert, Jordi; Llombart, Núria; Jofre Roca, Luis
    IEEE International Symposium on Antennas and Propagation
    Presentation's date: 2012-07
    Presentation of work at congresses

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    A near field imaging system for THz tomographic imaging based on a MST retina (an array of real antennas) has been designed. The main adva ntage of this implementation is the absence of microwave transmission line distribution networks and the capability to perform high speed imaging. The aim of this paper is to describe the design of the retina in order to maximize the performance of this im aging system.

  • Tomographic imaging retina at 100 GHz

     Alonso, Maria; Garg, V; Romeu Robert, Jordi; Llombart, Núria; Jofre Roca, Luis
    International Conference on Infrared, Millimeter, and Terahertz Waves
    Presentation's date: 2012-09
    Presentation of work at congresses

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    This paper presents a tomographic system at 100 GHz for imaging based on MST technique. At 100 GHz, a good compromise is obtained between penetration and reso- lution for biomedical and non-destructive testing applications. Moreover, this system just requires low frequency wiring and reduces the RF equipment necessary for performing real-time imaging. The system has been built and successfully validated with a set of measurements for a canonical scenario.

  • Water infiltration detection in civil engineering structures using RFID

     Capdevila Cascante, Santiago; Roqueta Crusats, Gemma; Guardiola Garcia, Marta; Jofre Roca, Luis; Romeu Robert, Jordi; Bolomey, Jean Charles
    European Conference on Antennas and Propagation
    Presentation's date: 2012
    Presentation of work at congresses

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  • UWB brain differential imaging capabilities

     Guardiola Garcia, Marta; Jofre Roca, Luis; Capdevila Cascante, Santiago; Romeu Robert, Jordi
    European Conference on Antennas and Propagation
    Presentation's date: 2012
    Presentation of work at congresses

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  • Real time 100 GHz MST imaging retina

     Alonso Del Pino, Maria; Garg, V.; Garcia Guerra, Carlos Enrique; Romeu Robert, Jordi; Llombart, Núria; Jofre Roca, Luis
    European Conference on Antennas and Propagation
    Presentation's date: 2012-03-26
    Presentation of work at congresses

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    A real time tomographic imaging system at 100 GHz based on a retina and Modulated Scattered Technique (MST) is presented in this paper. It consists in applying a low frequency modulation to each probe of an array of antennas in order to coherently detect the electric field by a collector. This system just requires low frequency wiring and reduces the RF equipment necessary for each pixel for a planar surface. The aim of this paper is to analyze the performance of different tomographic imaging processes for the imaging system described.

    A real time tomographic imaging system at 100 GHz based on a retina and Modulated Scattered Technique (MST) is presented in this paper. It consists in applying a low frequency modulation to each probe of an array of antennas in order to coherently detect the electric field by a collector. This system just requires low frequency wiring and reduces the RF equipment necessary for each pixel for a planar surface. The aim of this paper is to analyze the performance of different tomographic imaging processes for the imaging system described.

  • Terahertz graphene optics

     Rouhi, N.; Capdevila Cascante, Santiago; Jain, D.; Zand, K.; Wang, Yung Yu; Brown, E.; Jofre Roca, Luis; Burke, P.J.
    Nano research
    Date of publication: 2012-10
    Journal article

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  • Circular beam-steering reconfigurable antenna with liquid metal parasitics

     Rodrigo Lopez, Daniel; Jofre Roca, Luis; Cetiner, Bedri Artug
    IEEE transactions on antennas and propagation
    Date of publication: 2012-04
    Journal article

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    A novel antenna reconfiguration mechanism based on the displacement of liquid metal sections is presented. The liquid nature of the moving parts of the antenna helps avoid the main disadvantage of mechanically-actuated reconfigurable antennas which is the mechanical failure of their solid parts due to material fatigue, creep or wear. Furthermore, the displacement of liquid elements can be more effectively performed than in the case of solid materials by applying precise microfluidic techniques such as continuous-flow pumping or electrowetting. The reconfiguration mechanism is demonstrated through the design, fabrication and measurement of a radiation pattern reconfigurable antenna. This antenna operates at 1800 MHz with 4.0% bandwidth and is capable of performing beam-steering over a 360 range with fine tuning. The antenna is a novel circular Yagi-Uda array, where the movable parasitic director and reflector elements are implemented by liquid metal mercury (Hg). The parasitics are placed and rotated in a circular microfluidic channel around the driven element by means of a flow generated and controlled by a piezoelectric micropump. The measured results demonstrate good performance and the applicability of the microfluidic system.

  • 3-D microwave magnitude combined tomography for breast cancer detection using realistic breast models

     Guardiola Garcia, Marta; Capdevila Cascante, Santiago; Romeu Robert, Jordi; Jofre Roca, Luis
    IEEE antennas and wireless propagation letters
    Date of publication: 2012
    Journal article

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  • Analysis of the electromagnetic signature of reinforced concrete structures for nondestructive evaluation of corrosion damage

     Roqueta Crusats, Gemma; Jofre Roca, Luis; Feng, M.Q.
    IEEE transactions on instrumentation and measurement
    Date of publication: 2012-04
    Journal article

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    This paper presents a nondestructive corrosion damage detection method for reinforced concrete structures based on the analysis of the electromagnetic signature of the steel rebar corrosion. The signature of the corrosion on the scattered field upon microwave illumination is first numerically analyzed. First-order quality factor parameters, the energy and the mean propagation delay, are proposed to quantify the corrosion amount in the structure. To validate the model, low-profile ultra-wide-band antennas (3–12 GHz) are fabricated and measured. Measurements on 12 reinforced concrete samples with induced corrosion are performed, using three different antenna setups. The experiments demonstrate a good correlation between an increase in the corrosion amount with a decrease in the energy and an increase in the time delay of the propagated signal.

  • Efficient parametric characterization of the dynamic performance of an RFID IC

     Capdevila Cascante, Santiago; Jofre Roca, Luis; Romeu Robert, Jordi; Bolomey, Jean Charles
    IEEE microwave and wireless components letters
    Date of publication: 2012
    Journal article

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    In this letter, a measurement technique for a complete parametric characterization of the input impedance of an RFID IC is presented. The use of an SPDT switch to modulate the signal from the network analyzer provides the capability to measure the RFID IC activation level and its input impedance simultaneously. This data can then be used to fully predict the dynamic response and performance of an RFID tag.

  • CMOS processing for MEMS devices and their applications

     Montanyà Silvestre, Josep
    Defense's date: 2012-01-18
    Department of Electronic Engineering, Universitat Politècnica de Catalunya
    Theses

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  • Microwave Propagative Imaging for Nondestructive Evaluation of Concrete Structures

     Roqueta Crusats, Gemma
    Defense's date: 2012-07-19
    Department of Signal Theory and Communications, Universitat Politècnica de Catalunya
    Theses

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  • Fellow de l¿IEEE

     Jofre Roca, Luis
    Award or recognition

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  • Member IEEE APS AdCom Committee

     Jofre Roca, Luis
    Award or recognition

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  • A parasitic layer-based reconfigurable antenna design by multi-objective optimization

     Yuan, Xiaoyan; Li, Zhouyuan; Rodrigo Lopez, Daniel; Mopidevi, Hema Swaroop; Kaynar, Oguz; Jofre Roca, Luis; Cetiner, Bedri Artug
    IEEE transactions on antennas and propagation
    Date of publication: 2012-06
    Journal article

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    A parasitic layer-based multifunctional reconfigurable antenna (MRA) design based on multi-objective genetic algorithm optimization used in conjunction with full-wave EM analysis is presented. TheMRA is capable of steering its beam into three different directions simultaneously with polarization reconfigurability having six different modes of operation. The MRA consists of a driven microstrip-fed patch element and a reconfigurable parasitic layer, and is designed to be compatible with IEEE-802.11 WLAN standards (5–6 GHz range). The parasitic layer is placed on top of the driven patch. The upper surface of the parasitic layer has a grid of 5 5 electrically small rectangular-shaped metallic pixels, i.e., reconfigurable parasitic pixel surface. The EM energy from the driven patch element couples to the reconfigurable parasitic pixel surface by mutual coupling. The adjacent pixels are connected/disconnected by means of switching, thereby changing the geometry of pixel surface, which in turn changes the current distribution over the parasitic layer, results in the desired mode of operation in beam direction and polarization. A prototype of the designed MRA has been fabricated on quartz substrate. The results from simulations and measurements agree well indicating 8 dB gain in all modes of operation.

  • Frequency and radiation pattern reconfigurability of a multi-size pixel antenna

     Rodrigo Lopez, Daniel; Jofre Roca, Luis
    IEEE transactions on antennas and propagation
    Date of publication: 2012
    Journal article

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    Pixel reconfigurable apertures constitute one of the most adaptable structures regarding antenna reconfiguration, being capable to achieve frequency and pattern compound reconfiguration. However, pixel antennas require a large amount of switches (typically above 100) that severely impact the antenna efficiency, complexity, cost and reconfiguration time. This paper presents a novel technique to mitigate the inherent complexity of pixel antennas by including multiple sized pixels divided over driven and parasitic regions. The technique has been applied to a planar monopole architecture leading to a low-complexity prototype of small dimensions and requiring only 12 switches. Its reconfiguration properties have been fully characterized through exhaustive measurements. Frequency reconfiguration is achieved from 1 GHz to 6 GHz with simultaneous beam-steering capabilities, being capable of synthesizing at each frequency an omnidirectional pattern and up to 5 directive patterns steered towards directions covering an angular range of almost 180 .

  • Silicon micro-lens antennas for THz integrated arrays

     Alonso Del Pino, Maria; Llombart, Núria; Lee, Clement; Jung, C.; Chattopadhyay, G.; Jofre Roca, Luis; Mehdi, Imran
    International Conference on Infrared, Millimeter, and Terahertz Waves
    Presentation's date: 2011
    Presentation of work at congresses

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    In this paper, we describe the characterization of silicon micro-lenses fabricated by two different techniques, one using laser micromachining and the other developed using photolithographical techniques. The micro-lens antenna patterns were measured from 530 to 600 GHz and the characteristics of the two lenses compared.

    In this paper, we describe the characterization of silicon micro-lenses fabricated by two different techniques, one using laser micromachining and the other developed using photolithographical techniques. The micro-lens antenna patterns were measured from 530 to 600 GHz and the characteristics of the two lenses compared.

  • Micrometric deformation imaging at W-Band

     Abril, Jordi; Nova, Enrique; Broquetas Ibars, Antoni; Aguasca Sole, Alberto; Romeu Robert, Jordi; Jofre Roca, Luis
    IEEE International Microwave Workshop
    Presentation's date: 2011-08-24
    Presentation of work at congresses

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    The measurement of scattered signals at W Band can be exploited to form images of small deformations with precisions in the order of tenths of micrometers. In this paper an Interferometric Synthetic Aperture Radar setup is proposed to form high resolution reflectivity images and deformation maps of dielectric or metallic surfaces. First, the system geometry of observation based on a linear motion of the radar antennas is described. A CW frequency domain measurement provides the wide band required for high resolution imaging. The scattered field data is focused on the surface spatial domain using a combination of range compression based on Inverse Fourier Transform combined with a backprojection algorithm to form the synthetic aperture with a high cross range resolution. The focusing performance has been assessed by numerical simulations and experimental measurements of simple scattering objects like spheres and trihedrals. Interferometric images of controlled displacements have been obtained showing a good agreement between real and measured displacements. A representative surface deformation test has been also carried out using a metallic rough surface. The interferometric phase difference between acquisitions can be used to image local deformations in the order of tens of micrometers from a range of several meters. Likewise the interferogram coherence shows the degree of decorrelation of the radar reflectivity which provides valuable information for surface random change assessment.

  • The ¿challenging¿ world of Terahertz radiation and imaging

     Jofre Roca, Luis; Romeu Robert, Jordi; Capdevila, Santiago; Abril, Jordi; Nova, Enrique; Alonso, Maria
    European Conference on Antennas and Propagation
    Presentation's date: 2011-04-15
    Presentation of work at congresses

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    THz propagation through materials may reveal unique macroscopic and physical properties of their internal structure without the damage associated with ionizing radiation. The generation, radiation, and detection of THz signals relays into an intermediate region between microwave and optical frequencies seen as a transition in device physics from classical transport to quantum transition. The physical properties and parameters of the antennas and electronic devices at these frequencies (0.1-10THz) will we compared with their microwave and optical counterparts, the important differences highlighted and its significance in terms of spectral bandwidth and signal-to-noise ratio for near and short range imaging systems reviewed. Finally, some of the recent significant developments in the field will be summarized and the potential applications and future challenges and opportunities identified.

  • Antenna reconfigurability based on a novel parasitic pixel layer

     Rodrigo Lopez, Daniel; Damgaci, Yasin; Unlu, M.; Cetiner, Bedri Artug; Romeu Robert, Jordi; Jofre Roca, Luis
    European Conference on Antennas and Propagation
    Presentation's date: 2011-04
    Presentation of work at congresses

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    A novel reconfiguration method based in the use of pixel surfaces as parasitic elements is presented. This concept can be used to provide reconfigurability to a wide variety of non-reconfigurable antennas without requiring additional modifications on the basic antenna design and avoiding any physical interconnections. General guidelines are provided for the design of parasitic pixel surfaces. Reconfigurability of a parasitic pixel layer used in conjunction with a patch antenna is analyzed. Results demonstrate simultaneous frequency and radiation pattern reconfiguration with capabibity of providing till a 10% frequency tuning range and beamsteering over 30º.

  • 100 GHz retina for THz tomographic imaging

     Maria, Alonso; Guerra, C; Nova, Enrique; Abril, Jordi; Romeu Robert, Jordi; Llombart, Núria; Jofre Roca, Luis
    International Conference on Infrared, Millimeter, and Terahertz Waves
    Presentation's date: 2011-10-07
    Presentation of work at congresses

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    In a tomographic imaging system, the key is to collect a sufficient number of scattered field points to recover the currents in the inverse scattering problem. This can be accomplished by using a real array of multiplexed antennas for real time imaging. In this paper, a W-Band Retina for Terahertz tomographic imaging is presented. A system based on a retina, a collector and an illuminator is described and the results of a fabricated retina are shown.

  • Broadband conductivity of graphene from DC to THz

     Rouhi, N.; Jain, D.; Capdevila Cascante, Santiago; Jofre Roca, Luis; Brown, E.; Burke, P.J.
    IEEE International Conference on Nanotechnology
    Presentation's date: 2011
    Presentation of work at congresses

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    In this paper for the first time we have studied the broadband sheet conductance of few-layer graphene on single-crystal quartz substrate. Few-layer graphene was grown on Nickel coated Si wafers and transferred to the target substrate, which is single crystal quartz. High frequency measurements at X-band (8-12 GHz), using WR90 waveguide were performed. In addition, sheet resistance at W-band (75-100 GHz) and 1 THz range is also measured providing a comprehensive frequency sheet conductance calculation. The sheet resistance is extracted form the transmission coefficient (S21). The results present small variation at different frequency bands, and are quite stable within the bands.

  • W-band radiometric imager with mechanical beam-scanning

     Nova, Enrique; Abril, Jordi; Romeu Robert, Jordi; Broquetas Ibars, Antoni; Torres Torres, Francisco; Jofre Roca, Luis
    International Conference on Infrared, Millimeter, and Terahertz Waves
    Presentation's date: 2011-10-02
    Presentation of work at congresses

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    The design of a 94 GHz Total Power Radiometer system for imaging purposes is presented in this paper. A mechanical beam-scanning antenna system is used to acquire passive raster images. The main performance parameters of the imaging system are described as well as their impact on the resulting image quality. A temperature resolution below 1K and a spatial resolution around 4 cm at 1 meter standoff distance are obtained with this system. Moreover, radiometric images acquired in indoor and outdoor environments are shown and compared.

  • Characterization of a 94 GHz radiometric imager with mechanical beam-scanning

     Nova, Enrique; Abril, Jordi; Romeu Robert, Jordi; Broquetas Ibars, Antoni; Torres Torres, Francisco; Jofre Roca, Luis
    IEEE International Microwave Workshop
    Presentation's date: 2011-08-24
    Presentation of work at congresses

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    This paper presents the characterization in terms of spatial resolution and radiometric sensitivity of a W-band Total Power Radiometer (TPR). The TPR is based on a heterodyne receiver with 64 dB of gain and 6.5 dB of noise figure. An antenna system consisting on a pan-tilt scanner has been designed and built in order to aim a 100 mm offset parabolic reflector. With this system, relative temperature images of targets at a 1 m standoff range are obtained in indoor environments with an spatial resolution of 4 cm.

  • Passive RFID based sensing

     Capdevila, Santiago; Jofre Roca, Luis; Romeu Robert, Jordi; Bolomey, Jean Charles
    IEEE International Conference on RFID-Technologies and Applications
    Presentation's date: 2011-11-16
    Presentation of work at congresses

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    The principle of communication of passive RFID, which relies on the Modulated Scattering Technique (MST) to transmit the information from the tag to the reader, opens a way to enable conventional RFID for sensing purposes, without any additional circuitry. In this paper a short description of the physical principle behind the sensing is presented along with measurements of RFID tags used for sensing in multiple applications, such as electromagnetic field measurement temperature or presence detection.

  • Deforming and relief interferometric SAR imaging at W-band

     Abril, Jordi; Nova, Enrique; Broquetas Ibars, Antoni; Aguasca Sole, Alberto; Romeu Robert, Jordi; Jofre Roca, Luis
    International Conference on Infrared, Millimeter, and Terahertz Waves
    Presentation's date: 2011-10-02
    Presentation of work at congresses

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    Interferometry at W Band can be exploited to form images of small deformations with precisions in the order of tenths of microns and retrieve surface relieves. An Interferometric Synthetic Aperture Radar setup is proposed in which the scattered field is focused using a combination of range compression and backpropagation algorithm. Interferometric images involving micrometric displacements have been obtained showing a good agreement between real and measured displacements. A metallic rough surface deformation test has been first performed, by imaging the phase difference between acquisitions before and after the displacement. The interferometric phase difference between acquisitions can be used to image local deformations from a range of several meters. Furthermore the interferogram coherence shows the degree of decorrelation of the radar reflectivity which provides valuable information for surface random change. Likewise the relief of the surface with an L-shape target is retrieved mapping the phase difference between the two receiving antennas, in this case an static scenario is required.

  • INTEGRATED RADIANT SYSTEMS DESIGN FOR WIRELESS SENSORS

     Serrano Calvo, Raquel
    Defense's date: 2011-07-22
    Department of Signal Theory and Communications, Universitat Politècnica de Catalunya
    Theses

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  • Multi-element arrays in subway environments

     Alonso Valdesueiro, Javier
    Defense's date: 2011-02-02
    Department of Signal Theory and Communications, Universitat Politècnica de Catalunya
    Theses

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