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A coplanar waveguide (CPW) fed polarization reconfigurable antenna for WLAN 2.4 GHz operation is studied. To achieve reconfiguration between left‐hand circular polarization (LHCP), right‐hand circular polarization (RHCP), and linear polarization (LP) with broad CP and LP operating bandwidths, the technique of switching only two PIN diodes embedded between the CPW feeding line and an open square‐ring radiating element is introduced. As the radio frequency (RF) and direct current (DC) signals must be fed from the same feeding line (input port), during the experiment, an additional Bias‐Tee element is introduced to the input port for combining the two signals. [ABSTRACT FROM AUTHOR]

A circularly polarized (CP) meander loop antenna design for GNSS applications is presented. The antenna size is 52.5 × 52.5 × 0.76 mm3 and it is placed 10 mm above a 100 × 100 mm2 metal plane. The proposed antenna utilizes a meandered loop antenna and has applied a perturbed element into the loop to excite two equal electric fields with near 90° phase difference, thereby radiating a good CP radiation. In addition, a triangular patch is loaded to the two diagonal corners of the loop are for improving the CP performances, as well as maintaining its CP radiation even under the interference of a large metal surface beneath it. The simulated 10 dB impedance bandwidth of proposed antenna was 2.2% (1.557–1.593 GHz), and the measured one was 2.4% (1.553–1.591 GHz). The simulated and measured 3 dB AR bandwidths were 0.8% (1.57–1.583 GHz) and 1.02% (1.567–1.583 GHz), respectively. Last, the proposed antenna is suitable for GNSS application that has large metal surface/ground, such as the roof of a vehicle. [ABSTRACT FROM AUTHOR]

This paper proposes an absorption-transmission-absorption (A-T-A) type frequency-selective rasorber (FSR) with high selectivity that is loaded above a polarization conversion structure (PCS) and applied to a circular polarization (CP) slot antenna array for ultra-wideband radar cross section (RCS) reduction. Outside the operational frequency band (out-of-band) of the antenna, the energy of the incident electromagnetic (EM) wave is directly absorbed by the FSR, whereas from within the operational frequency band (in-band) of the antenna, the incident EM wave penetrates the FSR and irradiates it on the PCS placed on the lower layer of the FSR structure, which meets the phase cancellation condition and is diffused at the same time, thereby realizing the in-band RCS reduction. Due to the lower insertion loss in the passband, higher quality factor (Q value) in the transmission band, and wider absorption band, the proposed FSR can minimize the gain loss (only 0.2 dB) of the CP slot antenna array and widen the RCS reduction bandwidth to 135.5% (5–26 GHz). In addition, due to the central symmetry of the FSR and PCS structures, the CP slot antenna array has monostatic RCS reduction performance for both horizontally polarized (HP) and vertically polarized (VP) incoming waves. [ABSTRACT FROM AUTHOR]

The design of a simple ultrahigh frequency RFID (radio frequency identification) reader antenna that can operate within the North America RFID band (902-928 MHz) is studied. To generate circular polarization (CP) radiation in this band, a novel method of loading two narrow open-ended slots (slits) into an eccentric annular slot patch is proposed. To allow optimum impedance matching with enhanced CP bandwidth, the radiating patch is loaded to an L-shaped ground plane. From the experimental results, the proposed antenna can yield an impedance bandwidth (10-dB return loss) between 650 MHz to 1125 MHz, while good CP bandwidth (3-dB axial ratio, AR) from 901 MHz to 930 MHz is also attained. Furthermore, gain level and efficiency of more than 7.8 dBic and 90%, respectively, were also measured. By simply removing one of the slits, this proposed antenna can also be modified to operate within the China (840-846 MHz) and European (865-868 MHz) RFID band. [ABSTRACT FROM AUTHOR]

A low profile annular-ring patch antenna with circularly polarized (CP) radiation for radio frequency identification (RFID) reader applications in the ultra-high frequency (UHF) band (922-928 MHz) is presented in this article. Perturbation method is applied by loading a pair of triangular open-notch into the outer circumference of ring patch, and good impedance matching can be determined by using the coupled feeding technique. The overall size of this proposed antenna is 150 mm × 150 mm × 10.4 mm. The measured results show desirable 10-dB impedance bandwidth and 3-dB axial ratio (AR) bandwidth of 3.5% (908-941 MHz) and 0.65% (922-928 MHz), respectively. Stable antenna peak gain and efficiency of 7.2 dBic and 87% are also exhibited, respectively. [ABSTRACT FROM AUTHOR]

ABSTRACT A microstrip-fed circular slot antenna design is proposed. To excite good CP (circularly polarized) radiation, the technique of loading a cross patch (with unequal arm lengths) into the circular slot is initially applied. Here, good impedance matching can be further attained by dividing the cross patch into two equal sections with a gap loaded in between them, in which this gap will induce a capacitive loading effects on the proposed antenna. The measured results shown that the proposed antenna has 10 dB impedance bandwidth of 36.4% (2116-3124 MHz), and its corresponding CP bandwidth (along 3 dB axial ratio, AR) was 12.3% (2345-2655 MHz). In addition to that, the proposed CP slot antenna has also yielded peak gains of more than 3.3 dBic across the CP bandwidth. Detailed process of designing the proposed CP slot antenna is explicitly shown, and vital parametric studies were also conducted by simulation. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:715-720, 2016 [ABSTRACT FROM AUTHOR]

ABSTRACT A microstrip-fed conventional annular ring slot (ARS) antenna with linear polarization (LP) is initially studied. To generate two orthogonal degenerate modes for circular polarization (CP) radiations, two identical meandering perturbation slots (MPS) are symmetrically loaded into the ARS. By further incorporating a PIN diode switch across each MPS, the proposed antenna can switch between left-hand CP (LHCP), right-hand CP (RHCP), and LP. All three polarizations have shown good impedance bandwidth and broad CP bandwidth that can satisfy the wireless local area network (WLAN) 2.4-GHz operating band (2400-2480 MHz). Furthermore, desirable gains of 1.8-2.0 dBi and 2.40-2.84 dBic are also exhibited at LP and LHCP/RHCP, respectively. © 2015 Wiley Periodicals, Inc. Int J RF and Microwave CAE 26:110-120, 2016. [ABSTRACT FROM AUTHOR]

ABSTRACT The design of a small size 50 × 50 mm2 coplanar waveguide-fed square ring slot antenna is studied. To attain circular polarization (CP) radiation with broad 3-dB axial ratio (AR) bandwidth that can cover the worldwide interoperability for microwave access 2.3 GHz (2305-2320 MHz, 2345-2360 MHz) and wireless local area network 2.4 GHz (2400-2480 MHz) bands, a novel technique of extending a C-shaped branch from the vertical monopole is proposed. Good impedance matching and CP performance was achieved by further extending a vertical tuning strip from the C-shaped branch. From the measured results, 10-dB impedance bandwidth and 3-dB AR bandwidth of 63.89% and 7.93% were achieved. Furthermore, stable gain variation of approximately 2.7 dBic and radiation efficiency of more than 85% were also exhibited across the bands of interest. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:886-891, 2015 [ABSTRACT FROM AUTHOR]

ABSTRACT A simple circularly polarized (CP) square loop antenna for UHF band RFID tag is proposed to overcome the polarization mismatch problem between reader antenna and tag antenna. To achieve good CP radiation, an open gap is introduced onto the square loop. Also, the technique of loading a matching stub across the RFID chip is applied to the proposed loop tag antenna, and good impedance matching between the antenna and RFID chip can be achieved by tuning the matching stub. The proposed loop tag antenna shows desirable antenna gain and good reading distance performance, and its measured reading distance reaches to 17.6 m. Therefore, the proposed antenna is an excellent candidate for various RFID applications in the UHF band, especially those that may require long reading distance. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:2335-2341, 2014 [ABSTRACT FROM AUTHOR]

The design of a simple UHF (ultrahigh frequency) RFID (radio frequency identification) reader antenna that operates within the 900 MHz band (902–928 MHz) is studied. To generate circular polarization (CP) radiation, a novel method of loading a semicircular slot into the main circular radiating patch is proposed. To allow optimum impedance matching with enhanced CP bandwidth, the L-shaped probe-feed technique is employed in this design. From the experimental results, besides achieving a gain level of more than 7 dBic, the proposed antenna can also yield an impedance bandwidth (10-dB return loss) from 880 to 1100 MHz, while good CP performances between 901 to 930 MHz are exhibited. To further validate the experimental results, parametric studies are also carried out via simulation. [ABSTRACT FROM PUBLISHER]

A square patch passive RFID tag antenna designed for UHF band is presented in this article. To achieve compact size and circular polarization (CP) radiation, the square patch is embedded with a cross slot, while an L-shaped open-end microstrip line linked to a tag-chip and terminated by a shorting pin is capacitively coupled to the patch. By selecting an appropriate length for the microstrip line and its coupling distance with the radiating element, easy control on the input impedance of the proposed tag antenna which leads to excellent impedance matching is achieved. The measured 10-dB return-loss bandwidth of the tag antenna is 50 MHz (904–954 MHz), while its 3-dB axial-ratio bandwidth is 6 MHz (922–928 MHz). Further experiment shows that the tag antenna can provide better reading range when mounted on a metallic surface. [ABSTRACT FROM PUBLISHER]

The characteristics of circular-polarization (CP) square-ring microstrip antennas loaded with superstrate are studied in this paper. Firstly, several CP antenna prototypes with various substrate thicknesses and inner-slot sizes are designed, and they are excited by a coupling-strip feed in order to overcome the high-impedance problem of the square-ring microstrip antenna. Then, superstrates with different thicknesses and permittivities are attached to the antenna prototypes in order to evaluate their effects on the CP performances. The experimental results show that the effects are more obvious for the square-ring microstrip antenna with a larger inner-slot size. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 47: 567–570, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21231 [ABSTRACT FROM AUTHOR]

The design of a square-shaped patch antenna loaded with an Olympic-like logo slot for 900 MHz UHF RFID reader applications is studied.To achieve good circularly polarized (CP) radiation, an additional narrow perturbation slot is also loaded centrally across the logo. By further applying the L-shaped probe-fed method, desirable 3-dB Axial Ratio (AR) and 10-dB impedance bandwidth of 3.72% and 30%, respectively, can be achieved. From the experimental results, gain level and efficiency of more than 6 dBic and 89% were also measured, respectively. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:1358-1360, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27591 [ABSTRACT FROM AUTHOR]

An aperture coupled microstrip‐line fed antenna (circular patch) with CP radiation is initially investigated. To achieve good CP radiation at 925 MHz UHF RFID frequency, the technique of loading an inverted C‐shaped slit into the circular patch is initially proposed. By further loading an open eccentric‐ring shaped parasitic element around the circular patch, an additional CP frequency can be excited at 910 MHz, and by combining these two CP frequencies, broad CP bandwidth that can cover the entire 902‐928 MHz UHF RFID band is achieved. Because of the parasitic element, the total dimension of proposed antenna is modified to 170 × 170 × 11.4 mm3. From the measured results, the impedance and CP bandwidths of the proposed antenna were 9.4% (859‐944 MHz) and 3.1% (902‐930 MHz). Furthermore, its corresponding peak gain and efficiency are 5.9 dBic and 84.3%, respectively. Further analyses have shown that the proposed antenna can also achieve good CP frequency agility across the desired UHF RFID operating band (902‐928 MHz). [ABSTRACT FROM AUTHOR]