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In this letter, a design of broadband microstrip three‐way directional coupler (TWDC) is presented. The broadband performance of the microstrip TWDC is realized by the method of cascading multi‐section. The broadband TWDC is designed to achieve equal power division and −120°, 0°, and +120° phase differences between output signals. To verify the broadband design, a prototype of three‐section microstrip TWDC operating at C‐band is designed, fabricated and measured. The measured results show that the power division error of the designed broadband TWDC is less than ±0.7 dB and phase error is less than ±12° at a relative bandwidth of 16%. To verify its performance in multibeam application, the designed TWDC is used as a beamforming network for multibeam antenna array to generate three orthogonal beams. [ABSTRACT FROM AUTHOR]

This letter presents a wideband high gain substrate integrated waveguide horn antenna (SIWHA) loaded with half Maxwell fish‐eye (HMFE) fabricated by 3‐D‐Printing. The impedance bandwidth of the SIWHA is narrow, mainly caused by the discontinuity between the substrate with the air. By introducing the HMFE and a match layer between the SIWHA with HMFE, the impedance continuity can be realized, which can not only improve the impedance bandwidth but also enhance the antenna gain. Experimental results show that the proposed antenna can achieve more than 6 dBi gain and 60.9% relative impedance bandwidth with reflection coefficients lower than −10 dB. [ABSTRACT FROM AUTHOR]

A design of planar dual‐polarized differentially fed multibeam patch antenna array (DFMPAA) is presented in this article. The dual‐polarized DFMPAA is composed of two circular 4 × 4 butler matrixs (BMs) and a 1 × 4 dual‐polarized patch antenna array. The two BMs are designed in the top and bottom layer as the feeding network of horizontal polarization (HP) and vertical polarization (VP), respectively. The patch is designed as the radiation element of the dual‐polarized DFMPAA, which is fed by the slot and aperture coupling to generate the HP and VP wave, respectively. To achieve high cross‐polarization discrimination (XPD), the antenna element is fed differentially. A prototype working at 5.5 GHz is fabricated and measured in order to validate the performance of the proposed dual‐polarized DFMPAA. The dimension of the dual‐polarized DFMPAA is 3.8 λ0 × 1.7 λ0. Measured results show that when the beam scan to the maximal pointing angle, the XPD of the dual‐polarized DFMPAA in HP and VP are higher than 27 and 29 dB, respectively. Additionally, the beams of the dual‐polarized DFMPAA can cover the range of ±42° in horizontal plane. [ABSTRACT FROM AUTHOR]

In this article, a broadband dual circularly polarized (CP) antenna with simple structure and high gain is designed. A metal ridge septum with the shape of the cascade of a rectangle and a triangle is embedded into the square waveguide to excite CP wave, which is presented through analysis and simulation. By feeding the antenna at the two positions with respect to the symmetrical position of the septum, it can form the right‐handed circularly polarized (RHCP) and left‐handed circularly polarized (LHCP) wave, respectively. To verify the design, a prototype of the antenna is fabricated and measured. The measured and simulated results coincide with each other. According to the simulation and measurement, the designed antenna can work well within a relative bandwidth of 64% from 8.5 to 16.5 GHz. The proposed dual CP antenna has the simple configuration and good performance, and it can be a good candidate antenna for the broadband communication system. [ABSTRACT FROM AUTHOR]

In this paper, a wide-range leaky-wave antenna with fast scanning rate and open-stopband (OSB) suppression based on microstrip spoof surface plasmon polaritons (MSSPPs) is proposed. First, the high-scanning-rate theory is analyzed. And based on the theory, the MSSPPs is used to radiate the fan beam rather than quasi-omnidirectional beam. In order to suppress the OSB, a capacitive slot is introduced using the proposed method of impedance matching. The prototype of the proposed antenna is fabricated and the measured results show that the antenna has 140° scanning range from −72° to 68° with the scanning rate of 8.8 and reflection coefficient lower than −10 dB in 8.7–10.2 GHz. [ABSTRACT FROM AUTHOR]

ABSTRACT A high gain dual-polarized wideband Fabry-Perot (FP) antenna fed by 1 × 2 antenna array is proposed. A metasurface consisting of patch and mesh array is employed as a partially reflective surface, which produces a reflection phase with a positive slope over a wideband frequency range for increasing antenna's gain bandwidth. To obtain dual polarizations and further improve the gain of antenna, a 1 × 2 patch array coupled by two orthogonal slots is designed as the feed of the FP antenna. A prototype is fabricated and measured. The measured results demonstrate that this proposed antenna has a 3-dB gain bandwidth of 22.2% in both polarizations. The peak gain of 15.7 dBi and 15.2 dBi is obtained at two polarization ports, respectively. Within the 3-dB gain bandwidth, good impedance matching with high isolation over 35 dB between the two ports is achieved as well. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:2316-2321, 2016 [ABSTRACT FROM AUTHOR]

This paper presents a novel shared-aperture dual-band dual-polarized (DBDP) high-gain antenna for potential applications in synthetic aperture radars (SARs). To reduce the complexity of SAR antennae, a DBDP high-gain antenna based on the concept of Fabry–Perot resonant cavity is designed. This antenna operates in both $C$ - and $X$ -bands with a frequency ratio of 1:1.8. To form two separate resonant cavities, two frequency selective surface layers are employed, leading to high flexibility in choosing desired frequencies for each band. The beam-scanning capability of this proposed antenna is also investigated, where a beam-scanning angle range of ±15° is achieved in two orthogonal polarizations. To verify this design concept, three passive antenna prototypes were designed, fabricated, and measured. One prototype has broadside radiation patterns, while the other two prototypes have frozen beam scanned to +15°. The measured results agree well with the simulated ones, showing that the high gain, high port isolation, and low cross-polarization levels are obtained in both the bands. Compared with the conventional high-gain DBDP SAR antennae, the proposed antenna has achieved a significant reduction in the complexity, mass, size, loss, and cost of the feed network. [ABSTRACT FROM AUTHOR]

This paper presents a compact-size, low-cost smart antenna with electronically switchable radiation patterns, and reconfigurable polarizations. This antenna can be dynamically switched to realize three different polarizations including two orthogonal linear polarizations and one diagonally linear polarization. By closely placing several electronically reconfigurable parasitic elements around the driven antenna, the beam switching can be achieved in any of the three polarization states. In this design, a polarization reconfigurable square patch antenna with a simple feeding network is used as the driven element. The parasitic element is composed of a printed dipole with a PIN diode. Using different combinations of PIN diode on/off states, the radiation pattern can be switched toward different directions to cover an angle range of 0° to 360° in the azimuth plane. The concept is confirmed by a series of measurements. This smart antenna has the advantages of compact size, low cost, low power consumption, reconfigurable polarizations, and beams. [ABSTRACT FROM PUBLISHER]

Wearable systems are important for future smart home care for the disabled and ageing population. One of the key challenges is the power supply. One solution is to develop an energy harvesting system suitable for providing power wirelessly. The matching network and filter in traditional energy harvesting system occupy lots of space, introduce additional losses, and reduce the total efficiency. This paper presents a novel filtering antenna suitable for wearable energy harvesting systems. The developed antenna has a broadband operation, harmonics suppression, compact size, and low cost. Firstly, a novel technique for broadband filtering antenna modeling and design in order to realize complex input impedance is presented. By adjusting the external quality factors and coupling coefficients of the resonators, complex impedance matching can be realized. Then, the theory of characteristic mode is used for the modal analysis of the filtering antenna. To verify the design concept, a C‐band circularly polarized filtering antenna with complex impedance is designed and fabricated. The results show that the impedance bandwidth is more than 14.5% with a peak gain higher than 8.5 dBi. The proposed antenna is conjugate matched to the rectifying circuit at 5.8 GHz and mismatched at the second harmonic frequency to suppress the harmonic reradiation, leading to a compact rectenna structure. [ABSTRACT FROM AUTHOR]