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A compact dual open-loop antenna is proposed to provide enhanced bandwidth in near-field applications in the ultra-high frequency band. The antenna generates a strong and uniform magnetic field in a near-field zone of the smaller open-loop antenna. For increased bandwidth, two open loops with individual half-wavelength perimeters are etched on each side of an FR4 printed circuit board. The antenna was fabricated in a compact overall size (dimensions, 60 × 60 × 0.8 mm3) and achieves an interrogation zone of 50 × 50 mm2 with good impedance matching and uniform magnetic field distribution in a 888–932 MHz band. Performance tests indicate that the proposed antenna has a reading distance of up to 130 mm for near-field applications and is suitable for radio frequency identification reader applications. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:2008–2012, 2015

A microstrip-to-slotline transition technique is presented, for the coupling of a circularly polarized circular slot antenna in the ultrahigh frequency band.The fundamental TE11 mode of the circular slot antenna is investigated, using the magnetic current flow in the slot. In the proposed design, circular polarization (CP) is generated using a proper c-strip metal, within the circular slot structure, and connecting a strip metal to the circular slot edge, at −45° to the feeding slotline. The direct slotline feed is coupled to a 50-Ω microstrip line, on the opposite side of the substrate. Simulated and measured results indicate that the proposed structure achieves good CP radiation, in the TE11 mode. The impedance bandwidth and the 3-dB axial-ratio bandwidth for the design are approximately 22.1% and 2.5%, respectively. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:2016–2023, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27013

A compact circularly polarized coplanar crossed dipole antenna with an unequal length of arms for RFID reader is designed and measured in this paper. It uses two unequal length dipoles connected in parallel to a coaxial cable feed and requires no matching network. The impedance bandwidth of the proposed antenna for S11

By using a pair of shorting pins, the dual-frequency operation of a single-feed rhombic microstrip antenna with a pair of slits is presented. This shorted dual-frequency microstrip antenna can result in a much reduced antenna size, and provide a tunable frequency ratio of ∼1.26–2.33 for the two operating frequencies by varying the inset slit length. Simulated results with the use of the software also have been conducted to study the characteristics of these antennas. Details of the proposed designs are described and discussed. © 2002 Wiley Periodicals, Inc. Microwave Opt Technol Lett 34: 183–186, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10411

A dual-mode bandpass filter (BPF) using the degenerate modes of a meander square-ring structure printed on the high-permittivity substrate is proposed. The dual-mode resonator is based on a square-ring loaded with two meander strips at the coupling sides. The filter is printed on the Al2O3 substrate with a permittivity of 9.8 and could be easily integrated with RF circuits. Besides its simple structure, the filter shows low insertion loss and small size, owing to the high-permittivity substrate used. The proposed filter shows a 6.3% bandwidth at the central frequency 2406 MHz, and it also provides transmission zeros on both sides of the bandwidth. Experimental results are in good agreement with simulated values. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 2117–2119, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23578

A novel microstrip-fed dual-band L-shaped monopole antenna has been developed for WLAN applications in the 2.4-GHz and 5.2-GHz bands. The antenna has a single L-shaped radiator and is easy to construct. The obtained impedance bandwidth (1:1.5 VSWR) reaches 15.6% and 12.6% for the 2.4 and 5.2 GHz, respectively. Omnidirectional patterns, vertical null in the antenna patterns, and good efficiency of the two operating frequencies are given for the proposed antenna. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 37: 214–216, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10873

A dual-frequency rectangular microstrip antenna with a pair of π-shaped narrow slots close to the nonradiating edges of the patch is experimentally studied. By varying the length and spacing of the two arms of each π-shaped slot, the proposed antenna provides a tunable frequency ratio from about 1.03 to 1.19. Details of the antenna design and experimental results are presented and discussed. © 2001 John Wiley & Sons, Inc. Microwave Opt Technol Lett 29: 195–197, 2001.

By embedding a pair of U-shaped narrow slots close to the nonradiating edges of a rectangular microstrip patch, a single probe-fed microstrip antenna for broadband operation is proposed. Measurements show that the antenna bandwidth can be as large as about 2.6 times that of a corresponding conventional rectangular microstrip antenna. Details of the proposed designs are described, and experimental results are presented and discussed. © 2000 John Wiley & Sons, Inc. Microwave Opt Technol Lett 27: 369–370, 2000.

A novel dual-feeding technique for a broadband circularly polarized aperture-coupled microstrip antenna operating in a 2.45 GHz system is presented. The dual feeds are placed in orthogonal directions, and are connected to a Wilkinson power divider with a 90° phase shift between its two output feedlines. Proper positioning of the coupling slots results in high port solution (>40 dB), and a purity of circular polarization is obtained. A broad impedance bandwidth (VSWR≤2) of about 54.7% and a 1 dB axial-ratio bandwidth of about 9.8% were achieved. © 2001 John Wiley & Sons, Inc. Microwave Opt Technol Lett 28: 100–101, 2001.