190 research outputs found
Design of a Low-Cost Microstrip Directional Coupler with High Coupling for a Motion Detection Sensor
A coupled-line coupler based on the asymmetric cascade connection of two coupled line sections is used to achieve a high coupling factor using low-cost material and technology in the X frequency band, and its performance is compared with a standard quarter-wave, coupled-line coupler, showing an increase in the coupling factor of about 3 dB. The proposed coupler can be effectively used in a Doppler motion detection sensor, due to its strong coupling and relatively high isolation. The coupler is designed through a simple, yet rigorous, equivalent circuital model. Then,anoptimizationprocedurewasperformedusingthecommercialsoftwareAnsysHFSSinorder to compensate for losses and second order effects. A prototype of the designed coupler was realized, and the measured data show very good agreement with simulations
Structure-Based Evolutionary Design Applied to Wire Antennas
A new design technique for antennas, namely the Structure-based Evolutionary Design (SED), is introduced and described in detail. SED is a new global random search method derived by the “genetic programming”, a strategy proposed by Koza. The proposed technique will be compared with the genetic algorithms (GA), a widely used design technique, showing the numerous advantages of our approach with respect to standard ones. SED assumes no “a priori” structure, but it builds up the structure of the individuals as the procedure evolves. Therefore SED is able to determine both the structure shape and dimensions as an outcome of the procedure (infinite-dimensional solution space), acting on subparts of the whole structure, and allowing to explore effectively the far more vast solution space.
We thoroughly discuss both the general features of SED and its application to wire antenna design. The antenna internal representation, which is a key to the successful implementation of SED, and the construction of fitness functions from the antenna specifications will be described in detail.
The proposed approach has been assessed with many different cases, using as design requirements both Gain and VSWR in a frequency band as wide as possible, and with the smallest size. The results obtained with SED are finally compared with other popular algorithms like Particle Swarm Optimization (PSO) and Differential Evolution (DE), showing that both the computational cost and the complexity are of the same order of magnitude, but the performances obtained by SED are significantly higher
A Multiband Printed Log-Periodic Dipole Array for Wireless Communications
A multiband printed Log-periodic dipole array (LPDA) antenna for wireless communications is presented. The antenna has been designed starting from Carrel's theory, optimized using CST Microwave Studio 2012, and then realized. The comparison between simulated and measured results shows that the proposed antenna can be used for wireless communications both in the S (2.4–3 GHz) and in the C (5.2–5.8 GHz) frequency bands, with very good input matching and a satisfactory end-fire radiation pattern. Moreover, it has a compact size, is very easy to realize, and presents an excellent out-of-band rejection, without the use of stop-band filters, thus avoiding interference out of its operating frequency band
Progettazione, sintesi,caratterizzazione e attivitĂ biologica di nuovi derivati 4-(3H)-CHINAZOLINONICI e METIL-SOLFONICI
A Wearable Textile RFID Tag Based on an Eighth-Mode Substrate Integrated Waveguide Cavity
A novel wearable textile Radio Frequency Identification (RFID) tag based on an eighth-mode substrate integrated waveguide cavity is presented. Antenna size reduction for effective operation in the [865-870]-MHz RFID UHF band is obtained by exploiting the H-field symmetry planes of a cylindrical Substrate Integrated Waveguide (SIW) cavity. High isolation from the human body and excellent robustness with respect to variations in antenna-body distance are achieved using an energy-based design strategy, aiming to reduce ground plane size. The resulting tag exhibits very low manufacturing complexity and may be produced at low-cost. Design and simulations were performed using CST Microwave Studio, and a prototype of the tag has been manufactured and tested in a real environment
Structure-Based Evolutionary Programming Design of Broadband Wire Antennas
A design technique for wire antennas, based on the Structure-Based Evolutionary Programming, is used to design a broadband antenna with an end-fire radiation pattern and a very simple geometry, operating in the 3–16 GHz frequency band, namely, from the S band to the Ku band. The antenna has been analyzed with NEC-2 during the evolutionary process, looking for high gain, good input match, and robustness with respect to realization tolerances. The outcome of our design procedure shows a very good performance
A Truncated Waveguide Fed by a Microstrip as a Radiating Element for High-Performance Automotive Anticollision Radars
A small truncated waveguide fed by a microstrip line through a transverse coupling slot is proposed and assessed as a high-performance antenna and array element in the K band and above. This antenna allows to obtain a high radiated power, with a very low cross-polar component in the radiated field. It is therefore particularly suitable for application in automotive anticollision radars. The proposed radiating element has been analyzed by a numerical code based on an in-house method of moments, and the microstrip feeding line has been modeled by its equivalent magnetic-wall waveguide. A linear array of such elements has been designed and matched with a BPF-inspired matching network allowing an in-band behavior suitable for anti-collision radar use, with an out-of-band rejection large enough to avoid the first receiving BPF
Design of Shaped-Beam Planar Arrays of Waveguide Longitudinal Slots
The Elliott's procedure for the design of a pencil beam waveguide longitudinal slot array has been generalized to encompass the design of shaped beam planar slot arrays. An extended set of design equations, taking into account in an operative way the feeding part of the array, has been devised. From this set of equations, a general and effective design procedure has been set up, shedding light on the constraints posed by a complex aperture distribution. The results of the proposed synthesis procedure have been validated through comparison with a commercial FEM software
Performance estimation of photovoltaic energy production
This article deals with the production of energy through photovoltaic (PV) panels. The efficiency and quantity of energy produced by a PV panel depend on both deterministic factors, mainly related to the technical characteristics of the panels, and stochastic factors, essentially the amount of incident solar radiation and some climatic variables that modify the efficiency of solar panels such as temperature and wind speed. The main objective of this work is to estimate the energy production of a PV system with fixed technical characteristics through the modeling of the stochastic factors listed above. Besides, we estimate the economic profitability of the plant, net of taxation or subsidiary payment policies, considered taking into account the hourly spot price curve of electricity and its correlation with solar radiation, via vector autoregressive models. Our investigation ends with a Monte Carlo simulation of the models introduced. We also propose the pricing of some quanto options that allow hedging both the price risk and the volumetric risk
A review on improved design techniques for high performance planar waveguide slot arrays
Planar waveguide slot arrays (WSAs) have been used since 1940 and are currently used
as performing antennas for high frequencies, especially in applications such as communication
and RADAR systems. We present in this work a review of the most typical waveguide slot array
configurations proposed in the literature, describing their main limitations and drawbacks along with
possible effective countermeasures. Our attention has been focused mainly on the improved available
design techniques to obtain high performance WSAs. In particular, the addressed topics have been
reported in the following. Partially filled WSAs, or WSAs covered with single or multilayer dielectric
slabs, are discussed. The most prominent second-order effects in the planar array feeding network
are introduced and accurately modeled. The attention is focused on the T-junction feeding the array,
on the effect of interaction between each slot coupler of the feeding network and the radiating slots
nearest to this coupler, and on the waveguide bends. All these effects can critically increase the first
sidelobes if compared to the ideal case, causing a sensible worsening in the performance of the arra
- …