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The article presents the results of the development and experimental study that characterize the prototype of dual-polarization Yagi-Uda antenna for the meter wavelength range, which receives/transmits and selects electromagnetic energy in two orthogonal planes of linear polarization without additional mechanical (electromechanical) intervention. The antenna is designed to be part of the command radio line equipment for receiving and transmitting telemetry information in digital format with high-speed flying objects that can rotate around the longitudinal axis and change their polarization during flight. [ABSTRACT FROM AUTHOR]

The radar of the Yagi-Uda antenna array offers useful traits for the detection of stealth targets. It employs the Very High Frequency (VHF) band, which has the advantage of counteracting stealth technology, as the shape of the target and the absorbing materials used for absorbing radar signals are less efficient against VHF. Moreover, the meter wavelength enables the radar to detect targets at distances exceeding those accessible to millimeter- and centimeter-wave radars. Nevertheless, the range of detection of this type of radar remains constrained and requires further development. The majority of current research is concentrated on the signal processing aspect, with less focus being placed on the antenna array. The antenna elements represent a crucial component of the radar station. This article presents a novel development of the traditional 16-element Yagi-Uda antenna array, which is commonly used in surveillance radar systems operating at a meter frequency band. The development is achieved through a modification of the previously mentioned antenna, which aims to increase the directivity of the antenna array, with a minimum cost and the same signal processing as the original antenna array platform. An additional two-row Yagi-Uda antenna array is proposed, comprising 14 elements in each row and an associated power unit. This modification is designed to enhance the pattern characteristics of the array. Simulation and measurement results for the pattern of the antenna indicate that the achieved gain for the proposed modification is more than 3 dB in compression compared to that of the traditional 16-element array. [ABSTRACT FROM AUTHOR]

The aim of this study is to develop a prototype that automatically improves the position of a Yagi-Uda antenna using a microcontroller and to illustrate its radiation pattern through the use of MATLAB®. This study is intended for students and professors in the electronics engineering field. This served as their educational materials for teaching antenna system principles and theories. Developmental and experimental methods were used to achieve the objectives. The materials and components generally used in this study are a Yagi-Uda antenna, stepper motor, Arduino Uno, L293D motor shield, USB TV stick tuner, slotted optocoupler, ADS1115, coax cable splitter, speaker stand, and timing belt. The statistical tool used in this study was a Z-test to find out if the experiment results were significant. In testing the effectiveness of the automatic antenna system, the TV display in every increment of 1.8° was taken. It was the basis for the effectiveness of the study. At 5% a/2 level (1.96), the computed z value is 1.76, which is less than 1.96. Therefore, there is no significant difference between the picture quality of the TV display at every angle and the desired angle with maximum reception of the signal with the integration of MATLAB®. [ABSTRACT FROM AUTHOR]

Technological advancements have fueled a growing demand for reliable mobile communication systems, highlighting the importance of wearable applications across various sectors, including biomedicine, military, and rescue services. This study underscores the crucial role of wearable antennas in addressing this increasing demand, with a specific focus on their design and development for Internet of Things (IoT) applications. The objective is to establish resilient communication links capable of operating effectively across diverse environments and weather conditions. Microstrip Yagi-Uda antennas, renowned for their directivity, lightweight construction, low profile, and cost-effectiveness, are the subject of investigation in this research. The study presents the simulated and fabricated design of a wearable microstrip Yagi-Uda antenna operating at 2.45 GHz. Three distinct substrate textile materials--100% polyester, cotton, and jeans--were examined and compared in the antenna design. Better performance was achieved with the 100% polyester substrate antenna design, boasting a gain of 8.8 dBi and a return loss of -33.9 dB at 2.45 GHz. [ABSTRACT FROM AUTHOR]

A wideband ultra-low-profile Yagi-Uda type of solar-cell integrated antenna is presented. The proposed antenna consists of a driver, reflector, and director, and is also designed to function as a solar cell. An ultra-low-profile copper indium gallium selenide (CIGS) based solar cell is used as a driver, and a slit is cut from it to make a built-in solar-cell antenna. A CIGS solar cell-based reflector and director are added to increase the impedance bandwidth and gain of the proposed antenna. A narrow slit is used, and the spacings between the reflector, driver, and director are minimized to increase the solar-cell form factor. A coaxial-to-microstrip line transition type feeding structure is used to excite the antenna, which is printed under the second substrate. Three RF decoupler circuits are designed for the driver, reflector, and director to separate the antenna functionality from the solar cell. The antenna has overall dimensions of $0.71~\lambda _{o} \times 0.61~\lambda _{o} \times 0.006~\lambda _{o}$ at 3.2 GHz. Furthermore, the proposed antenna design possesses a wide measured impedance bandwidth of 56.7%, radiation efficiency of higher than 90%, a maximum measured gain of 5.67 dBi within the impedance bandwidth, and a solar-cell form factor of 89.7% with no optical blockage.

We propose a miniaturized Yagi-Uda antenna with a reconfigurable operating bandwidth. The antenna miniaturization and bandwidth enhancement are achieved based on manipulating the shape and the position of the antenna reflector and director. Indeed, by coupling effects, three resonances are combined to broaden the impedance bandwidth without affecting much the radiation characteristics. On the other hand, the reconfigurability function is ensured based on the insertion of one varactor diode onto the antenna reflector. The measured results reveal that the proposed design has the merits of a miniaturized one-layer design with 75% size reduction compared with the conventional antenna, a measured peak gain of 4.57 dBi, a peak efficiency of 97%, a smoothly tunable relative bandwidth of 10% to 30%, and a simple DC-bias network with less lumped components. The proposed antenna may find its use in some wide-band unidirectional wireless applications covering the bandwidth 0.99 GHz to 1.34 GHz, for instance, in cognitive radio applications where the operating bandwidth can be reconfigured, accordingly. [ABSTRACT FROM AUTHOR]

This paper aims to design a receiving antenna for harvesting energy using the wireless energy transfer (WET) method based on the ultra-high frequency (UHF) band. The study was conducted by comparing four types of receiving antenna design. A mathematical and experimental analysis has been done to evaluate the performance of the designed antennas. A Yagi-Uda antenna is utilized as the transmitter. The results show that the zig-zag type antenna has the best performance. It can receive electromagnetic energy from a transmitter with maximum efficiency is 0.1% for the receiving antenna volume of 0.34 cm3. The proposed method can meet the energy necessity of an implant device with a charging time of approximately 21.61 hours for the 700 mAh rechargeable battery capacity. As our preliminary conclusion, based on our results, this proposed method can be used as a reference for the practice in the WET field and the medical and restricted areas in the electromagnetic energy harvesting case. [ABSTRACT FROM AUTHOR]

This work presents a unique non-invasive method for monitoring glucose levels in blood using a planar Yagi–Uda antenna as a microwave sensor. The proposed antenna, operating at 5.5 GHz, exhibits a directional radiation pattern with a peak gain of 6.74 dBi. A low-cost FR4 material of size 30 mm × 40 mm × 1.6 mm is used as a dielectric substrate. A human finger phantom, comprising layers of skin, fat, blood, and bone, is created at 5.5 GHz in EM simulation tool for mimicking a real human finger. The finger phantom is positioned at different locations around the antenna and corresponding frequency shifts are remarked to a variation in glucose concentration from 0–500 mg/dL. An exemplary frequency shift of maximum 26 MHz is recorded when the phantom is placed at the bottom of the antenna. Time domain analysis is also carried out to understand the effect of glucose concentration variation on the output signal amplitude and delay. Simulated antenna results are found to be in stupendous agreement with the measured results. An experiment of placing a real human finger around the fabricated antenna also presents a splendid correspondence with the simulated results. Hence, this mechanism can be expedient for monitoring glucose levels in blood.

This work presents a non-invasive method to determine the glucose levels in blood samples using a planar Yagi-Uda antenna and a novel microstrip filter. The proposed antenna operates at 5.5 GHz and exhibiting uni-directional pattern giving a maximum gain of 6.74 dBi at the operating band. A commercially available and low-cost FR-4 substrate of dimensions 30 mm×40 mm×1.6 mm is used as a dielectric substrate. A finger phantom resembling a human finger is designed in the simulation environment, which consists of bone, skin, blood, fat as different layers. The glucose concentration is varied from 0 mg/dL to 500 mg/dL and the shifts in the frequencies are observed by keeping the phantom at various locations surrounding the antenna. A good frequency shift of 26 MHz is observed when the phantom is placed below the antenna. A good similarity is observed between the simulation and measurement results. Also, a novel microstrip filter, operating at 5.5 GHz, is developed, and the frequency shifts are studied by keeping a finger phantom at the top of the filter. The designed filter is shown to give a maximum frequency shift of 4 MHz when the glucose concentration changes from 250 mg/dL to 500 mg/dL. This study is supported by analysing transmission coefficient parameters and group delay characteristics.

In the era of digital transformation, Radio Frequency Identification (RFID) technology has emerged as a powerful enabler for a myriad of applications, from inventory management and supply chain logistics to access control and contactless payments. At the heart of this transformative technology lies the RFID antenna, a crucial component that facilitates wireless communication between RFID tags and readers. In this article, we delve into the intricacies of RFID antennas, their design principles, applications, and their profound impact on modern-day industries. [ABSTRACT FROM AUTHOR]

This work presents a non-invasive method to determine the glucose levels in blood samples using a planar Yagi-Uda antenna and a novel microstrip filter. The proposed antenna operates at 5.5 GHz and exhibiting uni-directional pattern giving a maximum gain of 6.74 dBi at the operating band. A commercially available and low-cost FR-4 substrate of dimensions 30 mm×40 mm×1.6 mm is used as a dielectric substrate. A finger phantom resembling a human finger is designed in the simulation environment, which consists of bone, skin, blood, fat as different layers. The glucose concentration is varied from 0 mg/dL to 500 mg/dL and the shifts in the frequencies are observed by keeping the phantom at various locations surrounding the antenna. A good frequency shift of 26 MHz is observed when the phantom is placed below the antenna. A good similarity is observed between the simulation and measurement results. Also, a novel microstrip filter, operating at 5.5 GHz, is developed, and the frequency shifts are studied by keeping a finger phantom at the top of the filter. The designed filter is shown to give a maximum frequency shift of 4 MHz when the glucose concentration changes from 250 mg/dL to 500 mg/dL. This study is supported by analysing transmission coefficient parameters and group delay characteristics. [ABSTRACT FROM AUTHOR]

This paper presents a pattern reconfigurable dual-polarized dipole antenna with staggered parasitic elements operating in 3.5 GHz band. The proposed antenna is designed by assembling two linearly polarized antennas to be orthogonally polarized, and each antenna includes two parasitic elements and a single dipole element. A circuit including a varactor is inserted into each parasitic element, and the current phase of the parasitic element changes according to the capacitance of the varactor. Each antenna has a beam steering range of about ±30° in the E-plane, and the beamwidth and gain are maintained uniformly regardless of the steering angle due to the angled parasitic element. Also, because of the continuously changing characteristic of the varactor, the beam of the proposed antenna is steered continuously, and only four varactors are used. The size of the fabricated dual-polarized antenna is $1.40\lambda _{0}\times 1.40\lambda _{0}\times 0.47\lambda _{0}$ , and the measured results confirm that the antenna has an average gain of around 6 dB with 0.3 dB gain variation.

In this work, 60-GHz wideband, compact vertically polarized end-fire monopole-based Yagi antenna-in-package is proposed for mobile devices. The antenna was arranged like a monopole array, and the size was minimized by utilizing the image effect. Advantages of the proposed antenna structure include reduction of bond-wire loss by inserting a cavity to make the antenna and chip the same height and size reduction due to image effect. For practical use, a proposed antenna is interconnected with CMOS chip via a bond-wire interconnect. The measured results show 4.99dBi peak gain with 3.5dB fluctuation within 60GHz unlicensed band. S11 bandwidth is 10.6GHz(57.6-67GHz) which corresponds to 16% fractional bandwidth. The total volume of the antenna is $0.74\times 1.14\times 0.15\lambda _{0}^{3}$ .

This article presents a technique for transforming the polarization of a pyramidal horn antenna by adding multiple layers of frequency-selective surfaces in front of the aperture, in order to rotate the direction of the electric field. Thus, two orthogonal components with the same magnitude, phase-shifted by 90°, are generated. Each frequency-selective surface consists of skewed λ/2 dipoles. Compared to other similar structures, our antenna system combines the field radiated from the horn aperture with the field scattered by parallel frequency-selective surface structures spaced on the same principle as that for designing a Yagi-Uda antenna array. The proposed horn antenna with multiple frequency-selective surfaces can be used as a feed element for a parabolic reflector antenna for maritime satellite communication systems in the X-band or in the lower part of the Ku band, or as part of a sensor for finding the direction of arrival of a wave, in order to orientate an antenna system. The concept was successfully validated on the basis of simulation and measurements. The proposed technique provides a close to unit axial ratio together with a 3 dB increase in gain compared to the conventional horn antenna, at low manufacturing costs. [ABSTRACT FROM AUTHOR]

A magnetic Yagi-Uda antenna applying higher order mode in millimeter-wave (mm-Wave) band with vertically polarized endfire radiation is proposed in this article. Surface wave mode analysis is applied to spot TE mode for magnetic Yagi-Uda antenna in contrast to TM mode for electric Yagi-Uda antenna. A modified structure evolved from conventional U-shaped cavity is used to address the reversed current issue for higher order mode, which exhibits a more uniform phase distribution at the Yagi-Uda array end. Then, a composite end-feeding structure with reflector integrated is further introduced to minimize its parasitic effects for practical antenna design in mm-Wave band. To validate the design, a prototype with a size of 2.7 $\lambda _{\mathbf {0}}\times1.25\lambda _{\mathbf {0}}\times0.088\lambda _{\mathbf {0}}$ is fabricated and tested. It can achieve anendfiregain of 8–11 dBi within 24–26 GHz with –10 dB impedance band covering an even wider frequency range. The measured front-to-back ratio (FBR) is larger than 16.1 dB. Vertically polarized radiation is realized with cross-polarization level lower than –20 dB atendfiredirection. [ABSTRACT FROM AUTHOR]

This paper proposes a millimeter-wave lens antenna using 3-dimensional (3D) printing technology to reduce weight and provide stable gain performance. The antenna consists of a four-layer cylindrical gradient-index (GRIN) lens fed by a wideband Yagi antenna. We designed a fractal cell geometry to achieve the desired effective permittivity for a GRIN lens. Among different candidates, the honeycomb structure is chosen to provide high mechanical strength with light weight, low dielectric loss, and lens dispersion for a lens antenna. Therefore, the measured peak gain was relatively flat at 16.86 ± 0.5 dBi within 25−31.5 GHz, corresponding to 1 dB gain bandwidth = 23%. The proposed 3D-printed GRIN lens is cost-effective, with rapid and easy manufacturing. [ABSTRACT FROM AUTHOR]

This paper describes an antenna design approach for achieving super directivity in an AESA (Active Electronic Scanned Array) radar using an unconventional 3D phased array (PA) antenna concept based on directional Yagi–Uda elements. The proposed scheme is shown to have a wider scanning feature, with higher directivity in comparison to the same geometry dipole array without increasing the element number. The antenna's microwave design includes an antipodal Yagi–Uda antenna element that is implemented efficiently on a microstrip PCB using a balun (balance–unbalance)-fed network. This type of antenna is valuable in restricted aperture scans for achieving a narrow antenna beam that increases the angular resolution and measurement precision of tracked targets and also enlarges the detection range or, alternatively, achieves the same performance with a lower number of elements—meeting the goal of low-cost production. The notable result of the high antenna directivity was obtained by both the element and the array architecture, which allowed for improvements in the Array Factor (AF) directivity by increasing the element's spacing and broadening the scan sector, achieved via the suppression of the element's Grating Lobe (GL). Another important benefit of this antenna design is the superior coupling reduction caused by its enlarged element distances, which are very significant in electronic scans. An outstanding opportunity to exploit this low coupling can be found in separated MIMO radar architecture. Other benefits of this design's architecture are the support of a combined module and antenna on a unified board thanks to the End-Fire radiation pattern, its low frequency sensitivity, and its low-cost manufacturing. [ABSTRACT FROM AUTHOR]

This communication presents an omnidirectional rectenna array with an enhanced RF power distributing strategy. The proposed rectenna array consists of three bidirectional subarray antennas, a $3\times $ 3 RF power distributing network, and a three-element rectifier array. Utilizing the $3\times $ 3 network to redistribute the varying RF power received by the three antennas, the RF-to-dc power conversion efficiency of the rectenna array can be enhanced under the illumination of electromagnetic (EM) waves with arbitrary incident angles. Measurement results reveal that the proposed rectenna array has an improved omnidirectional-harvesting capability compared with the design without RF power distributing strategy, thus can be readily used for RF energy-harvesting applications. [ABSTRACT FROM AUTHOR]

A novel design approach to high-gain, wideband, dual-resonant, closely-spaced, three-element Yagi-Uda antenna is advanced. The antenna is comprised by a full-wavelength, principal sectorial dipole, a circular metallic flat reflector, and a sectorial director. At first, a multi-source model is developed to predict the initial values of the key antenna parameters, e.g., the flared angle/radius of the director, and the separation between them. Then, as theoretically predicted, numerically simulated and experimentally validated, the flared angles of the principal radiator and the director are eventually determined as 270° and 180°, respectively. They are further tightly coupled at a close separation of 0.024-wavelength to yield relatively compact size and high gain simultaneously. Prototype antenna with a circular metallic reflector successfully exhibits an impedance bandwidth up to about 40%, with in-band maximum gain up to 10.4 dBi and gain fluctuation less than 3 dB. Finally, the antenna is comparatively studied with other Yagi-Uda antennas to highlight its unique wideband and high gain characteristics.

Low-profile shared-structure dual-polarized (DP) Yagi–Uda antennas are proposed, which are formed by three kinds of basic components, namely DP driven element, DP director, and DP reflector. An open-cavity dipole is utilized as the DP driven element to generate DP endfire radiations. The quarter-wave resonance mode for vertical polarization (VP) and half-wave dipole resonance mode for horizontal polarization (HP) are excited by differential feeding structures in the DP driven element. The open-cavity element is adopted as the DP director or reflector to enhance endfire gain. For the proposed design, two polarization radiators are integrated into one structure, realizing structure sharing, and thus a low profile. Three-element (Ant. 1) and seven-element (Ant. 2) antennas with a profile of 0.1 λ0 are designed, fabricated, and measured. The measured overlapped bandwidth of the Ant. 1 is from 4.11 to 4.83 GHz (16%) with ports isolation higher than 30 dB, and the measured VP and HP gains are from 5 to 6 dBi and 5 to 7 dBi, respectively. The Ant. 2 further increases the DP endfire gain by 2–3 dBi at the overlapped bandwidth of 16.3%. [ABSTRACT FROM AUTHOR]

Large-distance communications beyond a few meters is challenging for Terahertz (THz) signals because of high spreading loss and absorption in the media. The smart antenna concept used for RF antennas to improve the signal-to-interference/noise level can be extended to these THz antennas. Out of the two types of implementations of this concept, viz. (i) adaptive array and (ii) switched-beam antenna, this paper presents the switched-beam nanoantenna for the THz wave region. Based on the Yagi-Uda antenna concept, switched-beam graphene nanoantennas over silicon dioxide (SiO2) substrate is proposed in this paper. In one case (Antenna-I), the antenna is able to switch the beam in ± 90º directions, whereas in the other case (Antenna-II), the switching directions are 0º, ± 90º, 180º. This pattern reconfigurability can also be observed over a frequency range leading to simultaneous pattern and frequency reconfigurable nature of the nanoantenna. The reconfigurability is obtained by changing the graphene conductivity through its chemical potential. Due to plasmonic wave propagation in graphene at THz, the proposed graphene nanoantenna resonates at a sub-wavelength scale. Design aspects and the working principle of switched-beam graphene plasmonic nanoantennas in the THz region are discussed in this paper. [ABSTRACT FROM AUTHOR]

This paper presents a W-band planar type via-monopole based quasi Yagi-Uda antenna using metal coated through glass silicon via structures. The antenna was designed and fabricated on 350 μm thick borosilicate glass substrate, which has very low dielectric loss compared with silicon at millimeterwave frequencies. We used a microstrip line to feed the antenna, and the Yagi-Uda configuration using via structured radiator; reflectors; and director were fabricated using tungsten coated silicon via structures embedded in reflowed glass substrate with good high frequency characteristics. The proposed antenna achieved vertical polarization in planar configuration with height 0.09λo. High gain with end-fire radiation was achieved due to the Yagi-Uda configuration. Measured results confirmed the fabricated antenna operated in the W-band with 10 dB fractional bandwidth (FBW) of 12.5% from 76.3 to 86.5 GHz and peak gain of 7.82 dBi at 81 GHz in the end-fire direction. Thus, the proposed antenna with end-fire radiation will be useful for millimeter-wave onboard wireless communication, radar imaging, and tracking applications.

In the article the mutual coupling between radiators influence on electrical parameters of convex antenna array with doubly curved radiators placement surface is investigated. Yagi-Uda antennas are used as radiators. The integral equations method is incorporated.

This paper proposes a millimeter-wave lens antenna using 3-dimensional (3D) printing technology to reduce weight and provide stable gain performance. The antenna consists of a four-layer cylindrical gradient-index (GRIN) lens fed by a wideband Yagi antenna. We designed a fractal cell geometry to achieve the desired effective permittivity for a GRIN lens. Among different candidates, the honeycomb structure is chosen to provide high mechanical strength with light weight, low dielectric loss, and lens dispersion for a lens antenna. Therefore, the measured peak gain was relatively flat at 16.86 ± 0.5 dBi within 25−31.5 GHz, corresponding to 1 dB gain bandwidth = 23%. The proposed 3D-printed GRIN lens is cost-effective, with rapid and easy manufacturing.

A pattern-reconfigurable Yagi–Uda antenna based on liquid metal is presented. The antenna consists of a balun-fed active dipole and a pair of stretchable passive parasitic dipoles, which are implemented by eutectic gallium-indium (EGaIn) alloy embedded in microfluidic channels. The parasitic dipoles are driven at each end by two low-cost, three-dimensional printed media rods. Afterward, spinning the rods at different angles leads to varying degrees of stretching upon the stretchable dipoles. Note the length of passive parasitic dipoles is a vital factor for antenna radiation reconfiguration. The antenna exhibits bidirectional radiation if the parasitic dipoles are equal in length. Otherwise, directional radiation toward the shorter parasitic dipole direction can be obtained. Based on the above-mentioned working principle, a pattern-reconfigurable antenna working in wireless local area network (WLAN) band is fabricated and measured. Apart from the reconfigurable capability, the proposed antenna keeps operating in the WLAN band of 2.4–2.48 GHz during the whole shape deformation. [ABSTRACT FROM AUTHOR]

A novel combination of loop and dipole antennas into a Yagi-like structure is here investigated to implement a wearable antenna. The textile antenna is designed for being integrated into a smart glove together with a compact UHF-radio frequency identification (RFID) reader. A number of compact Yagi-like textile structures have been analyzed and compared, which consist of a rhombus-shaped folded dipole and parasitic elements acting as either a reflector or directors. The latter are needed to focus the field out of the operator hand, so limiting the radiation toward undesired directions. Four compact Yagi-like layouts (with one or two directors, with one director and one reflector, and with one reflector and two directors) are developed on a stretchable fabric and their performance is measured in terms of reflection coefficient and near-field distribution. Read range performance is measured by using COTS RFID reader and tags. [ABSTRACT FROM AUTHOR]

Since the Yagi-Uda antenna was created and published in the twenties, it has been a pillar of wireless communications and also one of the most popular antennas utilized due to its directivity and easy construction; although still commonly used today, one of the disadvantages is its laborious design process, especially when you have many directors. In recent decades, software has been developed to facilitate its design and simulation, both commercial and free to use software. This work describes the design of a Yagi-Uda antenna at 550 MHz using free MMana-Gal software. The results demonstrate that in instances where there is extreme precision or variability of materials is not required, free software can be an excellent option for design and simulation. [ABSTRACT FROM AUTHOR]

An annular array antenna is proposed in this letter. The proposed low-profile antenna produces an enhanced gain with omnidirectional vertically polarized radiation patterns. Center-fed via-shorted circular patch antenna with omnidirectional radiation pattern can be low profile and wide bandwidth but suffers from tilted beam leading to a low gain in the azimuth plane. To improve the azimuth gain, instead of the traditional way of increasing the profile, a low-profile omnidirectional director is exploited, which is basically a passive magnetic dipole consisting of an annular side-coupling open-cavity. Several directors cooperating with the driven element form the proposed antenna, whose working principle is similar to the Yagi–Uda antenna. A prototype with a low profile of 0.11 ${\lambda _0}$ is designed and fabricated. Measured results show that the prototype can realize −10-dB impedance bandwidth of 13% (4.72–5.42 GHz) and gain of 3.72 dBi at 5.34 GHz with good omnidirectivity. Compared with that of the driven element only, the omnidirectional azimuth gain is significantly improved within the bandwidth, with the maximum gain being enhanced from −4.2 to 3.72 dBi at 5.34 GHz. The proposed antenna is designed for a portable 5G sub-6 GHz wireless channel measurement application. [ABSTRACT FROM AUTHOR]

Different from the traditional reconfigurable antennas, in which PIN diodes are just used as switches, a novel method for achieving the reactance tuning is proposed, in which the impedance characteristics of the PIN diode in different working states are used to realize elements sharing. The mechanism of element sharing is explained by mathematical analysis, firstly. Then, the novel method of realizing element sharing based on the impedance characteristics of PIN diode is explained. By this way, reactance tuning can be easily achieved using PIN diode. Finally, a 360° beam switchable dipole antenna array is designed to illustrate the feasibility of the proposed method. The results show that gains of 7.8 dBi, and FBRs (front‐to‐back ratios) of greater than 19 dB are achieved by the proposed antenna. In particular, the maximum gain drop of the proposed antenna is less than 0.72 dB when switching between different working modes. [ABSTRACT FROM AUTHOR]

Package-integrated and ultrathin power dividers with footprint smaller than unit $\lambda ~_{0}~^{\mathrm{ 2}}$ at the operating frequency of 28-GHz 5G new radio (NR) n257 and n258 bands are presented for the first time for small-cell applications. These power dividers are also configured as antenna arrays using endfire Yagi–Uda antenna elements. Utilizing minimal matching techniques, two-, three-, and four-element antenna arrays are designed without compromising on the bandwidth of operation or electrical performance. These thin-film power dividers exhibit a cross-sectional height of $147~\mu \text{m}$ and can be implemented in the top metal layer of front-end module packages. Panel-compatible semiadditive patterning (SAP) process is utilized to realize these structures, which yields precise line space dimensions required for millimeter-wave (mm-wave) applications. This results in power dividers with low added insertion loss, low VSWR, and minimal phase difference between output ports. The added insertion loss is 25% less than similar structures reported on integrated fan-out architectures. The antenna arrays exhibit high gain and efficiency. Excellent model-to-hardware correlation is observed with multiple coupons of the same structure. Package-integrated power dividers and antenna arrays based on ultrathin laminated glass substrate represent a major step toward realizing compact mm-wave antenna-in-package for 5G small-cell applications. [ABSTRACT FROM AUTHOR]

A structure and power robust, circularly polarized (CP) stack Yagi antenna for radio frequency identification (RFID) reader application is proposed in this letter. To increase the bandwidth, a parasitic patch is added to an air-filled microstrip patch antenna to generate another resonance on the axial ratio (AR) curve. To increase its gain, a guiding patch is placed at a distance slightly below λ/4 away from the parasitic patch, which serves as the director of a common Yagi antenna. It increases the boresight gain by more than 1 dB. To fix the position and rotation angle of these three patches, a center column with a three-layer structure is applied. Also, to achieve better impedance matching, a shorting screw is added to the basic patch. The proposed antenna achieves a measured –10 dB impedance bandwidth of 5.3% (884–932 MHz), a 3 dB AR bandwidth of 4.8% (890–934 MHz), a peak gain of 9.8 dBic, and an efficiency of –0.42 dB at 915 MHz, which makes it very suitable for the 902–928 MHz ultra high frequency (UHF) radio frequency identification application. Its size is 0.73 × 0.73 × 0.33 λ915MHz (λ915MHz is the free-space wavelength at 915 MHz). The proposed antenna has an all-metal structure, which gives rise the characteristics of high mechanical strength, high power-handling, high radiation efficiency, easy to assemble and low fabrication cost. [ABSTRACT FROM AUTHOR]

In this letter, a rapid and easy fabrication approach of nonplanar Yagi–Uda antennas is presented. The presented nonplanar Yagi–Uda antenna has a three-layer configuration and consists of several fully and partially-filled vias including one pair of radiator vias, two partially-filled reflector vias, and two partially-filled director vias. All vias are fully or partially filled by the silver conductive polymer (silver conductive epoxy, or SCE). This new partial filling scenario is realized by squeezing a certain amount of SCE in the vias using an accurate pipette. A nonplanar Yagi–Uda antenna prototype is designed and fabricated to work within the X-band. A good agreement is achieved between the measured and simulated results, which confirms the reliability and robustness of this fabrication approach. The measurement results show that for a Yagi–Uda antenna with just two directors, a gain of 10.2 dBi is achieved. [ABSTRACT FROM AUTHOR]

This paper describes the development of a Fractal printed Yagi-Uda antenna for wireless local area network (WLAN) applications operating at 2.4 GHz frequency. In miniaturizing the dimensions of an antenna, fractal method is applied where the first iteration and second iteration is implemented. The Computer Simulation Technology (CST) software is used as the platform to design and simulate the antenna. The substrate material used is the FR-4 board which has a dielectric constant of 5.4, the thickness of 1.6 mm and tangent loss of 0.019. The antenna performance interm of the reflection coefficient, radiation pattern and gain are compared and analyzed. For the first iteration, 22.81% of reduction size has been achieved and 30.81% reduction of the antenna size for second iteration has been achieved. [ABSTRACT FROM AUTHOR]

This paper presents a compact planar Yagi-Uda antenna for terahertz applications at 300 GHz for maximum gain and minimum return loss by optimizing the spaces between directors' elements beside their lengths and widths. The antenna parameters are optimized using the adaptive chaotic fruit fly optimization algorithm (CFOA) as a recent evolutionary-based algorithm. To show the convergence capability of the CFOA, the results are compared with those obtained by other evolutionary algorithms such as particle swarm optimization algorithm (PSO). The optimized antenna showed a return loss of -53 dB with high antenna gain of 14.2 dB. This enhancement is attributed to the efficient coupling between optimized array elements as well as reduced side and back-lobe levels. The comparison between different algorithms showed that the CFOA technique is superior to other evolutionary algorithms such as PSO by 39%. [ABSTRACT FROM AUTHOR]

A compact four‐element wideband planar multiple‐input‐multiple‐output (MIMO) antenna is proposed. The radiating elements are half‐loop monopoles. In order to cover the 5.8 GHz WLAN band, an additional high‐frequency operation mode is excited by an inter‐connected coupling parasitic element, and the radiation gain attained is enhanced via the arrangement of elements. The proposed four‐element MIMO antenna operates in a wide frequency range of 4.58‐6.37 GHz (34.3%), which covers the 5.2/5.8 GHz WLAN band and 5.5 GHz WiMAX band. For each element, an average gain of greater than 3.18 dBi is achieved, and the envelope correlation coefficient (ECC) between elements is lower than 0.05. The overall size of the compact multiport antenna system is only 40 × 36 mm2 with minimum isolation of 19 dB between its elements and has no any complex decoupling structure. Since the antenna has a satisfactory MIMO performance and is easily integrated with a planar structure, it is an excellent candidate for the MIMO communications application. [ABSTRACT FROM AUTHOR]

In this paper, the design and implementation of a plasma antenna array using Yagi–Uda reflectors with beamforming is discussed. The structure consists of the circular array of plasma tubes enclosed a unipolar L-band monopole antenna. Beamforming is possible using stimulated plasma tubes. The combination of the above structure with plasma excitation controller provides smart beamforming and uses of the Yagi–Uda structure increases gain compared to previous models. An experimental model in the L-band is fabricated that shows a good agreement between simulated and measured results. [ABSTRACT FROM AUTHOR]

We present a rectangular loop Yagi–Uda antenna based on the three-dimensional (3-D) printing technology. The antenna comprises a ground plane, a rectangular loop driven element, and rectangular loop directors. The loop driven element is about λ0/20 above the ground plane and is fed by a 50 Ω microstrip feedline. We fabricated the Yagi–Uda antenna by two materials 3-D printing technology and the following chemical plating process. The measured results show the antenna's working frequency is at 2.392 GHz while the |S 11|, gain, and efficiency are –12.63 dB, 8.99 dBi, and 79.5%, respectively. The experimental results are in a good agreement with the design. Our loop Yagi–Uda antenna features good antenna performances, small size, and easy fabrication, which can be an excellent candidate for antenna arrays and applications that need directional radiation property. Our work paves the way to the application of 3-D printing technology in the field of antennas. [ABSTRACT FROM AUTHOR]

A low-profile planar Yagi–Uda antenna with exact endfire radiation and vertical polarization is presented in this paper. The concept is the combination of an aperture element and a novel vertical I-shaped resonator (VISR). The aperture acts as the driven antenna, which can be equivalent of a virtual magnetic dipole. The VISR array constructed with VISR unit cell is employed as a director or a reflector element depending on the resonant frequency of the unit cell, which consists of two identical rectangular metal conductors printed on both sides of a substrate and their electrical connection using via holes. Two prototype antennas are then designed, fabricated, and measured to test the validity of the operating principle. Antenna I with one director and one reflector achieves an endfire realized gain of 9.9–10.3 dBi and a front-to-back ratio (FBR) of more than 17.4 dB across 6.36–6.70 GHz. With four directors and one reflector, an endfire realized gain of 12.9–13.6 dBi and an FBR of more than 17.9 dB are accomplished by antenna II across 6.38–6.71 GHz. Moreover, a sensitivity analysis is implemented for the proposed antennas. Simulated results show that the standard PCB process is a reliable method for antenna fabrication. [ABSTRACT FROM AUTHOR]

In this letter, a beam-scanning seven-element microstrip quasi-Yagi–Uda antenna working at terahertz (THz) frequencies is presented. This antenna is printed on the surface of a silicon dioxide substrate. The directing elements are made from metal and extended to the length of the reflecting element by graphene. Metal and graphene strips are printed on the bottom of the dielectric substrate. The $H$ -plane radiation pattern of the quasi-Yagi–Uda antenna can be deflected from −70° to 70° by controlling the bias voltage of graphene on the upper and lower substrate surfaces. The proposed antenna configuration has potential applications in THz beam-scanning antennas. [ABSTRACT FROM AUTHOR]

Herein, a 2×2 subarray antenna is designed to implement a VHF band active electronically scanned array. The Yagi–Uda antenna is used as a radiating element. The bandwidth enhancement and miniaturization of the Yagi-Uda antenna are achieved by optimizing the diameter of a driven element and the length of a director. In addition, the grid reflector is utilized to improve the front-to-back ratio(FBR) and to reduce both the wind resistance and overall system weight. The fabricated 2×2 subarray antenna fully covers the VHF target band(0.98～1.02 fc). The measured maximum gain is 10.61 dBi and the FBR is larger than 26 dB. [ABSTRACT FROM AUTHOR]