dB Axial Ratio Beamwidth Research Articles

A Circularly Polarized Antenna Based on the Unidirectional Resonant Modes of a Ferrite Disk

We propose a circularly polarized antenna with a wide axial ratio (AR) beamwidth that consists of a normally magnetized ferrite disk mounted on a ground plane. The device uses the resonant modes of the disk, which rotate only in the clockwise or counter-clockwise sense in the frequency range where the effective permeability of ferrite is negative. A semianalytical model is derived for the antenna fed by a single, conventional current probe and is validated numerically by finite element method. For a yttrium iron garnet disk with the radius and height of 5 and 1 mm, respectively, the results show a 3 dB AR beamwidth of 90 ° with an operation frequency, which can be tuned in the 4-4.5 GHz range by varying the magnetic bias field from 50 to 35000 A/m. Simulations show that higher AR beamwidths are achievable using finite ground conductors. Compared with previous papers, the fabrication requirements on this structure are not critical, which enhances its potential applicability.

A BROADBAND CPW-FED CIRCULARLY POLARIZED SQUARE SLOT ANTENNA FOR UHF RFID APPLICATIONS

A broadband CPW-fed circularly polarized square slot antenna for ultra-high-frequency (UHF) radio frequency identiflcation (RFID) applications is proposed. It consists of a square slot embedded with a spur line along diagonal and an F-shaped feeding structure. The proposed antenna achieves an impedance bandwidth about 307MHz (34.6% @886MHz) and a 3dB axial ratio (AR) bandwidth about 232MHz (24.3% @954MHz). The 3dB AR beam-width is about 96 degrees over the UHF band of 840{960MHz. The proposed reader antenna based on CPW structure is easy to integrate. With the symmetry and bidirectional radiation pattern, there are less readers needed in some applications, such as access control, than the reader with unidirectional pattern, which will deflnitely decrease the implemented cost. Therefore, this universal design with desired performance across the entire UHF RFID band (from 840MHz to 960MHz) can be applied to all the UHF RFID applications worldwide. Detailed considerations of the design and main parameters will be studied in this paper.

Dual-band wide-beam crossed asymmetric dipole antenna for GPS applications

A dual-band, wide-beam, circularly-polarised crossed asymmetric dipole antenna is presented for global positioning system (GPS) applications. Each dipole arm has an asymmetrically barbed arrowhead and contains two different-sized printed-inductors to reduce the length of the primary radiating element and to achieve dual-band operation. At 1.575 GHz, the antenna has a gain of 7.5 dBic, a radiation efficiency of 97.4%, and a 3dB axial ratio (AR) beamwidth of 143° and 152° in the x-z and y-z planes, respectively. At 1.227 GHz, the antenna has a gain of 6.3 dBic, a radiation efficiency of 90%, and a 3dB AR beamwidth of 132° and 140° in the x-z and y-z planes, respectively.

Design of a Wearable, Low-Cost, Through-Wall Doppler Radar System

A novel, low-cost, low-weight, wearable Doppler radar system composed of textile materials and capable of detecting moving objects behind a barrier is presented. The system operates at 2.35 GHz and is integrable into garments, making it well-suited for usage in difficult to access terrain, such as disaster areas or burning buildings. Wearability is maximized by relying on flexible, low-weight, and breathable materials to manufacture the key parts of the system. The low-complexity Doppler radar system makes use of an array of four textile-transmit antennas to scan the surroundings. The beam emitted by this array is right-hand circularly polarized along all scanning angles and provides a measured gain of 9.2 dBi. At the receiving end, textile materials are used to develop an active wearable receive antenna, with 15.7 dBi gain, 1.1 dB noise figure, left-hand circular polarization, and a 3 dB axial ratio beamwidth larger than 50°. Several measurement setups demonstrate that the onbody system is capable of detecting multiple moving subjects in indoor environments, including through-wall scenarios.

Aperture‐coupled circularly polarized F‐slot microstrip antenna

AbstractA compact, aperture‐coupled, circularly polarized F‐slot microstrip antenna is proposed. The F‐slot is embedded in the square microstrip patch and fed using an aperture‐coupled feeding structure. The proposed antenna has a 4.87% (2.40–2.52 GHz) 3 dB AR (axial ratio) bandwidth with a 14.4% 10 dB return loss bandwidth. The gain within the usable bandwidth remains relatively constant at 6.0 dBic with a ±0.5 dB variation and a peak gain is 6.2 dBic at 2.42 GHz. The antenna ground plane size and foam substrate thickness represent about 53.3 and 7% of its wavelength at the operating frequency of 2.46 GHz, respectively. The 3 dB AR beamwidth is >90°. The patch size of the proposed antenna is reduced by 22.7% compared with a conventional square patch antenna. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 1100–1104, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24230

CP microstrip antenna with wide beamwidth for GPS band application

This paper presents a technique developed for increasing the beam width of the circularly polarised (CP) radiation. With a pyramidal ground structure and a partially enclosed flat conducting wall adopted the designed CP patch antenna has a height of about 0.121 only and exhibits a 3 dB axial-ratio beamwidth of more than 130deg. The experimental results for operating in the 1575 MHz GPS band are presented and discussed.

Low cross-polarised patch antenna with single feed

A probe-fed patch antenna that generates low cross-polarised radiated fields is presented. The probe is located in the centre of the patch conductor and a microstrip line within the patch is used to ensure that good impedance matching is achieved. Enhanced radiation performance of the printed antenna is demonstrated by theoretically and experimentally investigating a circularly polarised (CP) version of the probe-fed patch antenna and comparing the results with a conventional probe-fed CP patch. The new radiator has an axial ratio of less than 1.5 dB at broadside and a 3 dB axial ratio beamwidth of close to 200°.