Yagi-Uda Antenna Research Articles

Technical Aspects of 205 MHz VHF Mini Wind Profiler Radar for Tropospheric Probing

Wind profiler radars (WPRs) are the state-of-the-art technology used for continuous remote sensing of 3-D wind structures from near surfaces to a height of about 20 km. Depending on the magnitude of atmospheric turbulence, the size, power, and frequency of the radar can vary. In this letter, the technical aspects of the design and the development of a 205-MHz very high frequency WPR installed at Cochin (10.04° N, 76.33° E), India, for troposphere and lower stratospheric studies in the tropical monsoon region are presented. The stratosphere–troposphere (ST) radar at Cochin is unique because it is the first WPR in the world operating at 205 MHz with a bandwidth of 5 MHz. The mini WPR with 49 three-element Yagi-Uda antennas at 205 MHz is working successfully and providing accurate wind measurements from 1 to 3.5–8 km, depending on atmospheric conditions. WPR data are comparable with collocated high-resolution Global Positioning System radiosonde observations. The main ST radar with 619 antenna elements is in the installation stage and is expected to be operational within a period of six months.

Graphene-based Yagi-Uda antenna with reconfigurable radiation patterns

This paper presents a radiation pattern reconfigurable Yagi-Uda antenna based on graphene operating at terahertz frequencies. The antenna can be reconfigured to change the main beam pattern into two or four different radiation directions. The proposed antenna consists of a driven dipole radiation conductor, parasitic strips and embedded graphene. The hybrid graphene-metal implementation enables the antenna to have dynamic surface conductivity, which can be tuned by changing the chemical potentials. Therefore, the main beam direction, the resonance frequency, and the front-to-back ratio of the proposed antenna can be controlled by tuning the chemical potentials of the graphene embedded in different positions. The proposed two-beam reconfigurable Yagi-Uda antenna can achieve excellent unidirectional symmetrical radiation pattern with the front-to-back ratio of 11.9 dB and the10-dB impedance bandwidth of 15%. The different radiation directivity of the two-beam reconfigurable antenna can be achieved by controlling the chemical potentials of the graphene embedded in the parasitic stubs. The achievable peak gain of the proposed two-beam reconfigurable antenna is about 7.8 dB. Furthermore, we propose a four-beam reconfigurable Yagi-Uda antenna, which has stable reflection-coefficient performance although four main beams in reconfigurable cases point to four totally different directions. The corresponding peak gain, front-to-back ratio, and 10-dB impedance bandwidth of the four-beam reconfigurable antenna are about 6.4 dB, 12 dB, and 10%, respectively. Therefore, this novel design method of reconfigurable antennas is extremely promising for beam-scanning in terahertz and mid-infrared plasmonic devices and systems.

Direct and Efficient Optical Coupling Into Plasmonic Integrated Circuits From Optical Fibers

We demonstrate direct and efficient optical coupling from an optical fiber into plasmonic integrated circuits (PICs) at 1.55- $\mu \text{m}$ wavelength using ultra-compact plasmonic dipole nanoantennas. The PICs consist of slot waveguides with single-chip integrated Yagi–Uda antennas. To improve the optical coupling efficiency from optical fibers, we add 500-nm-thick Su-8 film with a high refractive index as the top cladding. We experimentally achieve 8.6% couple-in efficiency from a high numerical aperture fiber to the plasmonic slot waveguide and 46% total couple-out efficiency from the plasmonic slot waveguide. We also quantitatively characterize the dependence of the couple-in efficiency to the spot size of the incident light.

Microstrip‐fed complementary Yagi–Uda antenna

In this study, a microstrip-fed complementary Yagi–Uda antenna backed with milled cavities is presented. This antenna is intended to radiate as near as possible to the end-fire direction while keeping a low profile and small size. The radiator and reflector elements are U-shaped slots while the director is a rectangular slot. These slots are printed on top of a very thin bendable commercial substrate. The radiator is fed by a microstrip line printed on the bottom side of the substrate. A thick metallic plate in which cavities are milled is placed below the substrate and connected by pin wires to the upper metallisation of the substrate. An S-band prototype is designed, fabricated and measured providing an operational bandwidth of 3% around 2.44 GHz, a maximum gain of about 8 dBi is achieved in the main beam which points towards 46° away from the broadside direction. Finally, simulation results of array and different conformal configurations are presented demonstrating the advantages of the microstrip feeding and the thin substrate material. Bending of the antenna along H-plane and E-plane for different curvatures is evaluated.

Smooth Moves in Power Transition: New Yagi-Uda Antenna Design for Wireless Energy

During last year?s International Microwave Symposium (IMS) in Phoenix, Arizona, the IEEE Microwave Theory and Techniques Society held its fourth Student Design Competition (SDC) in the category Wireless Energy Harvesting. Seven teams from different countries presented their designs during IEEE Microwave Week 2015.

Исследование дипольных возбудителей многолучевых директорных антенн

Исследование дипольных возбудителей многолучевых директорных антенн

Wearable AMC Backed Near-Endfire Antenna for On-Body Communications on Latex Substrate

A near-endfire, artificial magnetic conductor (AMC) backed wearable antenna is proposed in this paper for wireless body area networks operating in the 2.4-GHz industrial, scientfic and medical (ISM) radio band. The latex substrate permittivity has accurately been characterized for realizing a flexible planar Yagi-Uda antenna printed on it using a large-area screen-printing process. The bidirectional-endfire radiation of Yagi-Uda antenna is changed to an off-axis near-endfire radiation using an AMC reflector also printed on latex. The antenna is separated from the upper AMC surface using flexible Styrofoam of thickness $0.044\lambda _{o}$ at 2.4 GHz for the best compromise between keeping the antenna structure low profile and achieving an off-axis beam-tilt radiation of $\sim 74^{\circ }$ toward the endfire direction. The 0° reflection phase single-layered AMC and double-layered AMC (D-AMC) surfaces are proposed to reduce the body-absorbed radiation and, consequently, minimize the peak specific absorption rate (SAR) level for 2.4-GHz frequency band. Antenna performance in terms of return loss, radiation efficiency, extent of frequency detuning, gain, and SAR level is studied for free space as well as the CST MWS tissue-equivalent voxel model for all the proposed antenna designs. Antenna deformation bending study when placed on the human body is also performed in this paper. The antenna design is first optimized and fabricated on printed circuit board to verify the concept and then designed over the latex for actual human on-body all-flexible configuration. The Yagi-Uda antenna backed with D-AMC reflector demonstrates the measured return loss bandwidth of 45 MHz (2.425–2.47 GHz) and the gain of 0.12 dBi in the endfire direction with an improved on-body (chest) radiation efficiency of 78.97% and a reduced peak SAR level of 0.714 W/kg (average over 10-g tissue) for the compact overall flexible latex antenna volume of $0.4\lambda _{o} \times 0.4\lambda _{o} \times 0.076\lambda _{o}$ at 2.4 GHz. To the best of our knowledge, this is the first latex-based endfire antenna for on-body 2.4-GHz wireless communications backed with an AMC periodic metamaterial surface.

Design equations for the Quasi Yagi-Uda antenna operating in the UHF band

Design equations for the standard Quasi Yagi-Uda antenna built on 60 mil FR4 are presented to be used on fixed wireless telecommunication systems, Wi-Fi, WiMAX and LTE. In this work, the design equations are systematically proposed for the band between 1 GHz and 3 GHz, where relative bandwidth is better than 39%, the cross-polarization is lower than - 15dB for every angle and frequency, the cross-polarization is lower than -25dB in the main lobe and a front to back ratio better than 12dB in all the bandwidth. Three antennas where designed, built and measured with the proposed equations at 1.5GHz, 2GHz and 3 GHz, showing good agreement with the simulation results.

Yagi–Uda optical antenna array collimated laser based on surface plasmons

The divergence and directivity of a laser with a periodic Yagi–Uda optical antenna array modulated surface are investigated by finite element method. The nanoparticle optical antenna arrays are optimized to achieve the high directivity and the small divergence by using of Helmholtz's reciprocity theorem. When the nanoparticle antenna replaced by a Yagi–Uda antenna with same size, the directivity and the signal-to-noise ratio of the modulated laser beam are notably enhanced. The main reason is that the directors of the Yagi–Uda antennas induce more energy to propagate towards the antenna transmitting direction. The results can provide valuable guidelines in designing collimated laser, which can be widely applied in the field of biologic detection, spatial optical communication and optical measurement.

Employment of New Techniques for Characterizing Indian MST Radar Phased Array

ABSTRACTScientific investigations of dynamical processes in the earth's atmosphere are being performed over the past two decades using a 53 MHz mesosphere–stratosphere–troposphere (MST) radar, which is located at Gadanki, India. This radar consists of a phased antenna array of 1024 Yagi-Uda antennas. Antenna phase calibration is an important aspect for accurate measurements of atmospheric parameters by phased array MST/ST radars. In this paper, we describe two newly employed techniques to calibrate the large phased array antenna system of the Indian MST radar and the results obtained by these techniques. A “total power radiometer” technique has been employed for the first time to calibrate the antenna pattern in the receive mode. Radio source Virgo-A has been used as source in the far field for this purpose. The new technique has enabled us to characterize for the first time the first side lobe level of the antenna pattern and also the beam pointing accuracy in the E-plane. In the receive mode, antenna pattern is characterized with a 3 dB full beam width of 2.8o, first side lobe level of −18 dB, beam pointing accuracy is better than 0.12o. While the beam width and beam pointing accuracy are found to be close to the design values, the first side lobe level is 2 dB higher than that expected. To characterize the two-way antenna beam, active radar experiments are conducted and beam pointing accuracy has been estimated to be ∼0.1o using radar echoes from the moon; again for the first time. Improvement of signal-to-noise-ratio is observed with the newly developed antenna phase calibration method that used receiver quadrature detector. The agreement in comparison of wind vector derived from radar observations and Global Positioning System (GPS)-radiosonde measurements shows the performance status of the array antenna with the applied phase calibration.

Design of a YAGI-UDA Antenna with Gain and Bandwidth Enhancement for Wi-Fi and Wi-Max Applications

There are various patch antennas used for Wi-Fi and Wi-MAX applications. But, the problems with them are low gain, low power handling capacity and hence, conventional yagi-uda antennas are used. Conventional yagi-uda antennas are used in applications where high gain and directionality are required. Generally, numbers of directors are added to increase gain of these antennas. But, here we present modified yagi-uda antennas, in which the gain and bandwidth can be enhanced by not adding additional directors. In this paper, we initially discuss the designs of various yagi-uda antennas with uniform, non-uniform spacings between directors and then we discuss their gain and bandwidth enhancement by various approaches. Simulation results show that, the proposed techniques can enhance gain as well as bandwidth when compared with the traditional yagi-uda antennas.

A Compact Yagi-Uda Type Pattern Diversity Antenna Driven by CPW-Fed Pseudomonopole

This paper presents two end-fed compact Yagi-Udatype pattern diversity antennas, which use a coplanar-waveguide (CPW)-fed printed pseudomonopole antenna (PPMA) as the driver element. The balun-less driver PPMA behaves like a folded strip dipole and adds to its compactness. A common mode/differential mode (CM/DM) decomposition of antenna current on PPMA is carried out to show that the CM current distribution is similar to the current distribution of an asymmetrically fed dipole. The designed three-element Yagi-Uda antenna operates in the 2.4-GHz band with F/B ratio of about 23 dB and gain of 7.3 dBi. The compact pattern diversity antennas are realized by using two Yagi-Uda antennas separated by a common reflector. Two diversity antennas are realized using two different arrangements of Yagi-Uda antennas. The separation between the constituent PPMAs is varied to study its effect on the isolation and element embedded efficiency. The better of the two diversity antennas has overall footprint area of 65 × 58 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> and the separation between two radiating elements is only 34 mm or 0.272 λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">o</sub> . The simulated and measured port isolation (|S <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">12</sub> |) between two diversity branches is about 35 and 27 dB, respectively. The signal envelope correlation is 0.018 and the embedded efficiency is about 93%.

A Yagi–Uda Antenna With a Stepped-Width Reflector Shorter Than the Driven Element

A Yagi-Uda antenna with a stepped-width reflector is presented. Totally different than the traditional ones, the proposed reflector is shorter than the driven element as a result of the stepped-width structure. To further understand its working mechanics, an equivalent circuit to a dipole with a parasitic element is employed to explain the shortened length of the stepped-width reflector. Then, the proposed stepped-width reflector, shorter than the driven element, was applied to design, fabrication, and measurement of a Yagi-Uda antenna. Measured results show a good agreement with the simulated ones. In particular, the total length of the reflector employed in the Yagi-Uda antenna is 50 mm, and that of the driven element is 53 mm, which verifies the shorter length of the reflector and benefits achieving a smaller size.

Design of a PIFA-Driven Compact Yagi-Type Pattern Diversity Antenna for Handheld Devices

This letter presents a compact folded-strip printed inverted-F antenna (FS-PIFA) having dipole-like radiation pattern. The designed antenna operates at 2.45-GHz band and offers 5.75% bandwidth. A parametric study of the FS-PIFA is presented to show the effect of symmetry on the quality factor. Next, an FS-PIFA-driven compact Yagi-Uda antenna is designed by using folded strips as passive elements. The dimension of the Yagi antenna is optimized using mutated particle swarm optimization (PSO) algorithm. The designed Yagi-Uda antenna operates in the 2.45-GHz band with front-to-back (F/B) ratio of 17 dB and gain of 4.6 dBi. Finally, a pattern diversity antenna is realized by placing two such Yagi-Uda antennas back to back with a common reflector. The diversity antenna is very compact, and it occupies approximately 41 ×68 ×5 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> volume. The port isolation is about 24 dB. The signal envelope correlation coefficient of the diversity antenna is found to be as low as 0.074.

Design of cloaked Yagi-Uda antennas

Exploiting the appealing features of the mantle cloaking approach, we propose a general procedure that allows designing Yagi-Uda antennas with low scattering profile. The proposed radiators are able to operate efficiently within a given frequency band, while being electromagnetically undetectable in another desired frequency range. The general design procedure of such cloaked antennas is first presented, considering that both antenna and cloak requirements must be simultaneously fulfilled. Then, we prove that a cloaked Yagi-Uda antenna can be installed in close proximity to other radiators without affecting their performance. Due to these unprecedented characteristics, the proposed radiators may have a strong impact in the design of compact overcrowded platforms for both terrestrial and satellite applications.

CPW Fed WLAN Monopole Antenna with Gain Improvement

Monopole antennas have been widely used in the telecommunication industry in recent years. Most of the monopole antennas are designed to operate at Wireless Local Area Network (WLAN) application which has the advantage of unlicensed Industrial, Scientific, Medical (ISM) bands. ISM bands include of IEEE 802.11 a/b/g WLAN standards which have different speed data rates and operating frequency. The current issue stated that people always complain about their WiFi's signal coverage which is normally low. In an effort to solve this coverage problem, improvement must be made on the antenna's gain. A conventional gain of a monopole antenna operated at 2.4GHz is normally 2 dBi. A coplanar waveguide (CPW) fed WLAN monopole antenna which is operated at 2.4GHz with gain improvement is designed. In this project, the gain is improved by using the parasitic element technique. The concept is based on the Yagi-Uda antenna which consists of reflector and directors. The simulated and measured gain achieved is 6.9 dBi and 7.9 dBi respectively. Hence, the gain increment is 5.9 dBi if compared to the conventional gain. The designed antenna produced a directional radiation pattern which covers almost 90° of the antenna's coverage area.

Bacteria Foraging Algorithm in Antenna Design

A simple design procedure to realize an optimum antenna using bacteria foraging algorithm (BFA) is proposed in this paper. The first antenna considered is imaginary. This antenna is optimized using the BFA along with a suitable fitness function formulated by considering some performance parameters and their best values. To justify the optimum design approach, one 12-element Yagi-Uda antenna is considered for an experiment. The optimized result of this antenna obtained using the optimization algorithm is compared with nonoptimized (conventional) result of the same antenna to appreciate the importance of optimization.

The Sectored Antenna Array Indoor Positioning System with Neural Networks

This paper presents a sectored antenna array indoor positioning system (IPS) with neural network (NN) technique. The hexagonal positioning station is composed of six printed-circuit board Yagi-Uda antennas and Zigbee modules. The values of received signal strength (RSS) sensed by wireless sensors were used to be the information for object’s position estimation. Two NN models, including NN with back-propagation (BP) learning algorithm and probabilistic NN (PNN), were applied to perform the positioning work for a comparison. In the experiments, an 8x8 square meters indoor scene was performed and 288 points and 440 points were experimented in this area. The positioning results show that both NN models have the average error less than 0.7 meter. In other words, the proposed positioning system not only has the high positioning accuracy, but also has the potential in real application.

Inkjet Printing of Multilayer Millimeter-Wave Yagi-Uda Antennas on Flexible Substrates

This letter presents two high-gain, multidirector Yagi-Uda antennas for use within the 24.5-GHz ISM band, realized through a multilayer, purely additive inkjet printing fabrication process on a flexible substrate. Multilayer material deposition is used to realize these 3-D antenna structures, including a fully printed 120- μm-thick dielectric substrate for microstrip-to-slotline feeding conversion. The antennas are fabricated, measured, and compared to simulated results showing good agreement and highlighting the reliable predictability of the printing process. An endfire realized gain of 8 dBi is achieved within the 24.5-GHz ISM band, presenting the highest-gain inkjet-printed antenna at this end of the millimeter-wave regime. The results of this work further demonstrate the feasibility of utilizing inkjet printing for low-cost, vertically integrated antenna structures for on-chip and on-package integration throughout the emerging field of high-frequency wireless electronics.

Design of Pattern Reconfigurable Printed Yagi-Uda Antenna

Design of Pattern Reconfigurable Printed Yagi-Uda Antenna