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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]

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]

A novel radiation pattern reconfigurable multiple-input multiple-output (MIMO) antenna based on the loading of water is presented. By altering the situation of loading and unloading the distilled water on the surface of the parasitic element, the function of the parasitic element can be switched between a director and a reflector. According to the Yagi-Uda principle, the antenna creates a directional radiation pattern in the azimuth plane through the electromagnetically coupled parasitic elements. A good direction is achieved with the front-to-back of 13 dBi. The MIMO antenna consists of 2 identical elements lying orthogonally to each other. As a result, high-isolation (>35 dB) and low-envelop correlation coefficient (ρe < 0.0001) between MIMO elements are obtained by orthogonal dual-polarization antenna element. Good agreement is achieved between the measured results and the simulated results. [ABSTRACT FROM AUTHOR]

ABSTRACT A printed-circuit differential-fed Yagi-Uda antenna is presented that features enhanced bandwidth by employing a parasitic quarter-wavelength coplanar stripline (CPS) resonator which adds one more resonant mode within the operating bandwidth. The proposed antenna is designed, fabricated and measured. Experimental results are in good agreement with simulations. In the band of 2.27-2.58 GHz, the return loss is better than 10 dB and the gain better than 6 dBi. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 59:156-159, 2017 [ABSTRACT FROM AUTHOR]

ABSTRACT A 4-element circular quasi-Yagi based multiple-input-multiple-output (MIMO) antenna system with loop excitation is presented. This wide dual-band antenna system covers 1.45-2.55 GHz and 3.707− 4.71 GHz bands covering GPS, GSM/EDGE, UMTS/HSDPA, Bluetooth, Wi-Fi and WiMAX bands. This antenna has an end-fire directional radiation pattern with front-to-back ratio (FBR) of 13.8 dB, minimum measured gain of 5.8 dBi and directivity of 7 dB at 2 GHz using one director element. The minimum measured efficiency across the two bands was 65%. The proposed antenna ensured good MIMO performance in terms of isolation and correlation. It has a minimum measured isolation of 18 dB across both bands. Due to its geometry configuration, pattern orthogonality is obtained which gives very low envelope correlation coefficient values not exceeding 0.1589 in both bands. The size of the MIMO antenna system is 263 × 263 mm2 thus making it suitable for wireless access points and on vehicle applications.© 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:2769-2774, 2016 [ABSTRACT FROM AUTHOR]

A three‐dimensional printing technology that can be applied to stereo antennas fabrication is presented. The main steps of the fabrication include printing antenna model by dual materials fused deposition modelling and the following selective chemical plating. As a demonstration of this powerful technology, a typical stereo antenna, the Yagi‐Uda antenna, is designed and fabricated. Measured results show the printed antenna has good performances and agree well with simulated results. The technology provides a simple, straightforward way for antenna fabrication, and is especially suitable for the fabrication of stereo structure antennas. [ABSTRACT FROM AUTHOR]

To solve complex antenna design problems, this article proposes a hybrid differential evolution algorithm (DE). The proposed method combines the DE with the simplified quadratic interpolation (SQI) to optimize the performance of the antenna. The DE is the global optimizer, and the SQI is used to fine tune. The hybrid DE is demonstrated on optimizing designing Yagi-Uda antennas and wideband patch antennas. Numerical results confirm that the proposed method is superior to or at least competitive with the original DE and other evolutionary algorithms in terms of convergence speed and solution quality. © 2009 Wiley Periodicals, Inc. Int J RF and Microwave CAE 2010. [ABSTRACT FROM AUTHOR]

A broadband Yagi–Uda antenna composed of an excited inverted-F element and two parasitic inverter-L elements, which is used for the antennas of the SSR (secondary surveillance radar) and equipped on an airplane, is proposed. By locating a director close to the excited inverted-F element, such as about 0.05λ0 for the array space between these elements, an antenna having a performance of the bandwidth of 18.8% and unidirectional pattern in this bandwidth is obtained with a total dimension of about 0.1λ0 (height) × 0.4λ0 (length). The validity of the calculated values is experimentally confirmed. © 2001 Scripta Technica, Electron Comm Jpn Pt 1, 85(1): 43–48, 2002 [ABSTRACT FROM AUTHOR]

A broadband Yagi–Uda antenna composed of several monopole elements is proposed. By locating the director close to the excited element and superposing the characteristics of the reflector in a lower band to those of the director in a higher band, a broadband property is obtained for both the input impedance and the unidirectional pattern. Analysis by the method of moments indicates that the Yagi–Uda antenna (type 1) composed of three monopole elements has a bandwidth of 1:1.67 for VSWR ≤ 2, 1:1.84 for Gd/Gr ≥ 9 dB, and more than one octave for Gd≥8 dBi, where Gd and Gr denote the directive gains in the front and back directions, respectively. It is also shown that the Yagi–Uda antenna (type 4) composed of five monopole elements has about one octave for a bandwidth of VSWR ≤ 2 and Gd≥8 dBi. © 2001 Scripta Technica, Electron Comm Jpn Pt 1, 85(1): 49–57, 2002 [ABSTRACT FROM AUTHOR]

A low-profile Yagi-Uda antenna composed of a driven inverted-F antenna and two parasitic inverted-L antennas, which is used for the antennas of SSR (secondary surveillance radar) and mounted on an airplane, is proposed. The wire antenna is analyzed by the moment method, while the printed antenna is analyzed by the FD-TD method. The wire-type antenna has Gd/Gr = 18.1 dB, Gd = 8.3 dBi, bandwidth defined by VSWR ≤ 2 is 9.6%, with dimensions of 0.08λ0 (height) × 0.51λ0 (length), where Gd and Gr denote the directive gain of director orientation and reflector orientation, respectively. It is also shown that the characteristics of a print-type antenna fabricated on a dielectric substrate (εt = 1.7) are similar to those of a wire-type antenna. © 1998 Scripta Technica, Electron Comm Jpn Pt 1, 81(12): 28–36, 1998 [ABSTRACT FROM AUTHOR]

This paper proposes a new small multisector antenna called MS-MPYA (multisector monopole Yagi-Uda array) for wireless LANs. MS-MPYA consists of a multisector monopole Yagi-Uda array on a circular finite ground plane. The horizontal radiation pattern of the MS-MPYA is largely determined by the multisector array setting effect. A numerical analysis shows that setting metallic fins between arrays is effective in eliminating the strong reflection that would otherwise cause pattern instability; when the metallic fins are set, the beamwidth is reduced in the horizontal plane due to mutual sector interaction. The MS-MPYA design method considers the variables of array length, ground plane length, reflector height, and fin length. We clarify that the MS-MPYA offers a much lower profile than corner reflector or horn antennas. © 1998 Scripta Technica, Electron Comm Jpn Pt 1, 81(12): 80–90, 1998 [ABSTRACT FROM AUTHOR]

The fundamental importance of the Yagi-Uda antenna is its structural simplicity and its director and reflector actions. To fully comprehend the working principle of this antenna, it is important to be able to visualize the radiation mechanism directly in the time domain. In this paper, transient analysis of the Yagi-Uda antenna is performed using the FD-TD method. First, the input impedances and directivities obtained by this method are compared with the moment method, good agreement was found between the two methods, and the validity of this method was demonstrated. Next, the quasi-impulse responses of the antenna are calculated. The field pattern obtained by this method was visualized in the time domain. The radiation from the antenna edge is shown in the early time responses, and dispersion of the pulse shape with the passage of time is shown in late time responses. Moreover, the difference of characteristics due to the length of parasitic elements is shown by time-domain observation. [ABSTRACT FROM AUTHOR]

A millimeter-wave imaging array is proposed in which many Yagi-Uda antennas are placed on a dielectric lens. By changing the dimensions of them antennas, the impedance matching with the detector is optimized. At the same time, a radiation pattern matched to the incident beam from the focusing optics is realized. The crosstalk between the adjacent detectors on the array is measured. An optimum spacing is derived and a good imaging property is realized. The present imaging array is suitable for MMIC and is applied in practice for plasma measurement for nuclear fusion research. [ABSTRACT FROM AUTHOR]

A switchable Yagi-Uda antenna prototype with radiation pattern reconfiguration is presented in this letter. The proposed reconfigurable antenna is based on the concept of switching between the reflector and director of a Yagi-Uda antenna using a radio frequency PIN diode. As a result, the minimum/maximum radiation can be steered towards desired signals or away from interfering signals in opposite directions. The measured 10 dB impedance bandwidth and gain are 210 MHz (7%) and 8.02 dBi at 3 GHz, respectively. Details of the antenna design and its performance are described and empirically analyzed. [ABSTRACT FROM AUTHOR]

An efficient scheme is proposed and implemented for studying electromagnetic scattering problems of complex wire structures over a wide range of incident angle. A set of linear vector basis functions is applied to discretize the complex structures. Moreover, a novel approach based on the compressed sensing (CS) technique is presented and used to form several new excitation sources, which include various spatial information to obtain several measurements. With the help of proper sparse representation, the real induced currents of any incident angles can be calculated by using the orthogonal matching pursuit technique (OMP). To demonstrate the efficiency and the accuracy of the proposed method, numerical simulations of a pair of Yagi‐Uda antenna, a pair of spiral antenna, and a pair of spiral antenna array are accomplished by the new scheme, and the radiation pattern and Radar Cross Section (RCS) of the antennas are accurately calculated. [ABSTRACT FROM AUTHOR]