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This paper discusses the challenges in accurately measuring the far-field performance of array antennas, which have become more complex and larger due to recent trends in increasing the number of elements and the antenna size. The far-field measurement method, which is a general method for measuring a radiation pattern in a far-field, is difficult to be utilized at a high frequency due to limitations in physical chamber size and difficulty in diagnosing an antenna. In order to improve these problems, a near-field measurement method is used as an alternative. Even though using a near-field measurement, the accuracy of the derived far-field pattern is reduced at low elevation angles due to zero-padding of data outside the measurement area. The integration of the near-field measurement with the source reconstruction is a promising approach to enhance the measurement limits of the far-field pattern analysis. This paper aims to extend the previous work to accurately predict the far-field radiation pattern, especially in the low elevation angles. The verification of the proposed method is performed for a standard gain horn and 4 by 4 patch array antennas, with and without beam steering. [ABSTRACT FROM AUTHOR]

Vehicles to everything (V2X) communication includes a variety of types, so wide-angle scanning is integral. For wide-angle scanning, the half power beam width (HPBW) of a single antenna must be wide. Moreover, the gain, low cross-polarization level, and impedance bandwidth are essential factors in high communication performance. In this paper, a wide-angle scanning phased-array system using an arc-shorted half-elliptic patch antenna at 5.8 GHz is presented. The design of both a single antenna and the entire phased-array system are covered, and to verify the design method, the proposed single antenna and phased array system were fabricated. The proposed antenna had 162 ∘ HPBW in the E-plane and 8.63 dBi of peak gain. Its fractional bandwidth was 5%, and the level of cross-polarization was −16.8 dBi. Furthermore, the measured 3 dB scanning angle of the phased-array system was from − 90 ∘ to 90 ∘ . The proposed system has wide-angle scanning. [ABSTRACT FROM AUTHOR]

In this letter, a 4 × 6 microstrip patch array antenna with a low sidelobe level (SLL) for dual linearly polarized synthetic aperture radar (SAR) is proposed. The low SLL in wide-band is obtained by implementing the Chevyshev taper distribution. An optimal approach to design an unequal-power symmetric microstrip divider for dual-polarization is employed in the same layer with high isolation between the polarizations. The proposed antenna consists of squared patches excited by aperture coupled slots. With the analysis of resolution, swath, and noise equivalent sigma zero (NESZ) of the SAR system, we selected the antenna parameters such as bandwidth, beamwidth, gain, and SLL. The proposed antenna has a more than 10 % bandwidth and peak gains of 18.2 dBi and 18.3 dBi in V and H-polarization, respectively. The measured SLL in both polarizations are under −21.1 dB in the E-plane and −17.0 dB in the H-plane at the 10 GHz. [ABSTRACT FROM AUTHOR]

This article presents a high-voltage switched oscillator (SO) with a quarter-wave open-circuited stub (OCS) for generating mesoband high-power microwave (HPM) pulses. Unlike the conventional SO, the proposed SO generates mesoband HPM pulses whose dc offset is greatly reduced because the OCS inserted between a charged transmission line and an antenna blocks the flow of the electric energy from a high-voltage power supply to the antenna. Thus, the proposed SO allows the insulation capability of the antenna to be increased and ground-loop-integrated-wideband antennas to be employed. The transient response of the proposed SO is theoretically analyzed to understand its operation mechanism. The results prove that the proposed SO is capable of producing mesoband HPM pulses with a damped rectangular pulse waveform without a high-voltage dc offset. Also, the amplitude and quality factor are discussed. Compared with the conventional SO, the proposed SO has a larger output amplitude and smaller quality factor. Here, the difference between the quality factors is negligible. In addition to the theoretical analysis, we simulated and fabricated the proposed SO. Consequently, the results of the circuit simulation and experiment demonstrated the validity of the proposed design concept. [ABSTRACT FROM AUTHOR]

This communication presents a drone-to-drone adaptive beam switched antenna with 360° beam coverage and dual polarizations. The proposed antenna maintains the all-around beam coverage with high directivity based on 16 concentric planar Yagi-Uda dipole array. The high gain dipole array beams are configured by eight vertical polarization elements and eight horizontal polarization elements with directors and reflectors. Depending on various communication environments, a single beam, multiple beams with identical polarization, or multiple beams with different polarizations can be adaptively controlled for highly reliable drone-to-drone communication. To ensure the compactness in the antenna array, 16 concentric planar antenna elements are arranged in an orthogonally crossed manner with optimized vertical and horizontal transition matching circuits. Each Yagi-Uda dipole element for vertical or horizontal polarization showed a measured peak gain of 6.35 and 6.40 dBi at 5.5 GHz, respectively. The proposed antenna was integrated with sub-6 GHz transceiver and microcontroller unit (MCU) to verify the switched beam performance with dual polarization. Also, the Tx and Rx operation at random beam conditions was tested by using two proposed antennas and showed an excellent performance from 5 to 6 GHz. [ABSTRACT FROM AUTHOR]

Analyzing antenna coupling is valuable in solving various problems of multi-antenna systems. Through existing studies based on the reaction theorem and infinitesimal dipole modeling (IDM), mutual admittance can be intuitively and efficiently calculated. Extending previous studies based on the reaction theorem and IDM, we propose a method for analyzing mutual admittance between antennas that are located in nonplanar skew positions. There are two main ideas in this paper. The first is IDM extraction using a segmented grid on an antenna computer-aided design (CAD). Using the triangular-meshed antenna CAD, the IDM is extracted on a grid which is equal to the antenna shape. The proposed grid scheme improves the modeling accuracy of the IDM compared to the previous grid schemes. The second idea is to apply a rotation matrix to the IDM for efficient calculation of the coupling of any two antennas with nonplanar skew positions. The strength of the proposed method is that it can predict the mutual coupling between the two antennas by using only independent information for each antenna. However, since only the independent information is used for each antenna, it can reflect only the first-order electromagnetic interaction. Therefore, the proposed method is effective only when the distance between the two antennas is sufficiently far so that the two antennas are regarded independent regardless of the distance variation. Coupling analyses based on these two ideas were performed using two types of antennas in two different cases. The results of the coupling analyses were validated through comparison with the method of moment (MoM) results obtained with the FEKO simulation tool. [ABSTRACT FROM AUTHOR]

ABSTRACT For avoiding a dead zone where the tag cannot be detected in the ultrahigh-frequency (UHF) radio frequency identification (RFID), a SELECTABLE SECTORAL ANTENNA ARRAY USING a QUADRUPLE FEEDING NETWORK FOR ITEM-LEVEL TAGGING IN UHF RFID APPLICATIONS is presented. The proposed antenna array consists of a 2 × 2 circular polarized quadrifilar spiral antenna array and a quadruple feeding network for multiple beams. It generates single, dual, and quad beams with a hemispheric coverage by a beam switching, and its maximum gain and 3 dB beamwidth are approximately 7.8 dBic and 60°, respectively. Compared with the conventional antennas, the proposed antenna array provides the improved tag identification with the dead zone avoidance in the reading range. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:1523-1526, 2015 [ABSTRACT FROM AUTHOR]

ABSTRACT A new four-port balanced antenna feeding network for switchable polarizations and high transmit/receive (Tx/Rx) isolation characteristics is presented. The proposed structure is configured by two switching mode hybrid matrices which consist of two 3-dB couplers and two SP4T switches, two directional couplers, and Wilkinson dividers. By controlling impedances of the switching mode hybrid matrices, different types of polarizations such as right-handed circular polarization, left-handed circular polarization, vertical polarization, and horizontal polarization can be generated with stable Tx/Rx isolation characteristics regardless of antenna impedance variations. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:17-23, 2014 [ABSTRACT FROM AUTHOR]

This paper describes the development and performance of a 2 by 4 element suspended microstrip patch antenna array with linear polarization. The proposed structure with a new geometrical composition of entire array possesses the advantages of being wide bandwidth, high gain, precise side lobe level control and low cross-polarization level. The measured antenna has the peak gain 14.12 dBi and the cross-polarization is lower than −16 dBi within the impedance bandwidth. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:825-829, 2013; View this article online at wileyonlinelibrary.com. DOI: 10.1002/mop.27423 [ABSTRACT FROM AUTHOR]

The design of an integrated rectangular microstrip patch array antenna with enhanced isolation characteristic between transmitter and receiver is presented to produce a full-duplex transceiver with transmit and receive operation at the same frequency and with the same polarization. This integrated circulator-like antenna has potential uses in both short-range communication systems and radar systems. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:973-976, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26727 [ABSTRACT FROM AUTHOR]

A new 24-GHz transceiver patch array with a balanced Tx leakage canceller insensitive to antenna impedance variation and mutual coupling among ports is proposed. Consisting of two quadrature hybrids, two ring hybrids, and 4-port feed antenna, high transmit/receive (Tx/Rx) isolation is maintained regardless of antenna impedance variation and antenna mutual coupling. The proposed 4-port feed antenna is configured by dual fed 2x1 patch array having 6.12 and 5.06 dBi of measured Tx and Rx peak gain, respectively. In addition, the proposed architecture undergoes no power loss because of load termination (usually 50 Ω) in both transmit and receive paths. The proposed architecture obtains the measured Tx/Rx isolation of more than −40 dB stable at 24 GHz regardless of the antenna impedance variation. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:559-562, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.25815 [ABSTRACT FROM AUTHOR]

Novel integrated planar monopole antennas with various microstrip resonators are presented. The proposed integrated antennas consist of wideband planar monopole antennas and electromagnetically coupled microstrip resonators producing band-notched characteristics. Various types of microstrip resonators such as open-circuited line resonator, short-circuited line resonator, closed-loop resonator and open-loop resonator are described. The proposed designs are suitable for wideband antennas with narrowband interferer rejection characteristic or multi-band antennas. [ABSTRACT FROM AUTHOR]

A coupled-line passive circulator is proposed for improving the TX/RX isolation of the UHF radio frequency identification (RFID) reader. The increased isolation is realized by generating and adding the canceling signal to the leakage. The input return loss of the reader antenna, which can degrade TX-to-RX isolation, as well as the inherently imperfect isolation characteristic of a coupled-line directional coupler, are included in the design of the coupled-line passive circulator. The proposed coupler exhibits up to 60-dB isolation characteristic with the mismatch of the employed reader antenna. The performance comparison between the proposed and the conventional coupled-line directional couplers shows a significant improvement in the leakage-to-signal ratio by up to 35 dB. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 2597–2600, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23705 [ABSTRACT FROM AUTHOR]

A wideband planar monopole antenna with an L-shape ground plane is presented. The antenna also has a frequency-notching characteristic. By etching a half-wavelength U-shaped slot in the interior of the radiation element, the frequency-notching characteristic has been created. This paper presents the design and experimental results of the proposed antenna. Moreover, the study also investigates the tuning effects of the geometry parameters on the impedance matching. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 46: 340–343, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20981 [ABSTRACT FROM AUTHOR]