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A novel broadband circularly polarized (CP) antenna is proposed. The operating principle of this CP antenna is different from those of conventional CP antennas. An off-center-fed dipole is introduced to achieve the 90° phase difference required for circular polarization. The new CP antenna consists of two off-center-fed dipoles. Combining such two...
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... can utilize the 90 • phase difference to achieve a new CP antenna. The 90 • difference in space is obtained by folding the off-center-fed dipole perpendicularly at its center, as illustrated in Fig. 5. Two folded off-center-fed dipoles are employed for gain enhancement and easy excitation (also see Section III). The separation of two folded dipoles is about 0.5λ. For a unidirectional radiation pattern, the new CP antenna is placed 0.3λ above a ground plane (or a reflector). The total length of each folded dipole is 0.77λ. The ...
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Citations
... Parasitic elements were investigated in research [14,15]. The authors in [16,17] used an offset feed to get a wider bandwidth. Next, a combination of modified fed line and annular ring slot radiator patches for ARBW enhancement was presented by Jia et al. [18]. ...
In this paper, the development of a new compact CP antenna for C band applications specifically, as a SAR sensor, is proposed. It works at a center frequency of 5.3 GHz with wide bandwidth and high gain, as required in a CP-SAR system. It uses two-staked substrates (lower and upper substrates) and has a compact size of 28 × 32 mm (0.49 × 0.56 λ0\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\lambda_{0}$$\end{document}). Applying two-staked substrates is addressed to widen the bandwidth. Three stages of development are applied to get wide bandwidth and high gain, such as modification of the radiator patch, shifting of the radiator patch, and adding the parasitic patch at the upper substrate. Adding a parasitic patch will provide higher gain and wider bandwidth. First, this proposed CP antenna has a wide bandwidth for both IBW and ARBW. The measured and simulated IBWs ( ≤\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\le $$\end{document} − 10 dB) are approximately 673 and 744 MHz, respectively. Moreover, the simulated and measured ARBWs (≤\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ \le $$\end{document}3 dB) are achieved around 548 and 536 MHz. Second, the VSWR values are less than 2 dB spanning from 4842 to 5563 MHz, with the VSWR at a center frequency of 5.3 GHz being around 1.2. Third, the simulated and measured gain is 6.9–7 dBic at a center frequency of 5.3 GHz. The proposed CP antenna has good characteristics and is suitable to be deployed as a CP-SAR sensor.
... 1 By optimizing the radiation structure, the CP bandwidth can be broadened in many earlier works. 2 For example, the slots with different shapes, 3 metasurface-based crossed dipole, 4,5 off-center-fed dipole, 6 polarized rotated metasurface arranged in a checkerboard pattern 7,8 are different configurations to achieve broadband CP performance. In the above design, the array antenna often has a wider CP bandwidth, which is also the design model in this letter. ...
This letter introduces a wideband circularly polarized (CP) array antenna for wireless communication application. The array consists of 2 × 2 sequentially rotated symmetric antenna elements and a wideband weakly coupled feed network providing stable 90° phase difference. By using the proposed feed network and introducing the slot coupling feed, the CP array antenna can achieve a wideband CP performance with a low profile of 0.03 λ0 (at 5.0 GHz). The proposed antenna exhibits the impedance bandwidth (IMBW) of 73.9%, axial ratio bandwidth (ARBW) of 53.6%, and 3-dB gain bandwidth (GBW) of 60% with the peak gain of 10.4 dBi and the maximum efficiency of 82%. The measured results are in good agreement with the simulated results, indicating that a promising application in compact wideband C-band wireless systems.
... In [9]- [11], by modifying the ground planes or the backed cavities, crossed dipoles are realized for wideband CP radiation. Two pairs of the off-center-fed dipoles in [12] are used to achieve broadband circular polarization. Crossed dual-dipoles [13]- [14] are presented to realize wideband CP antennas. ...
... However, all of these antennas have modified ground structures, such as the stair-shaped cavity [9], the crossed fin-shaped cavity [10], and the rotated shorted metal plates [11], which are bulky and difficult to be extended into the antenna array designs. The antenna reported in [12] have the similar relative bandwidth compared to the presented antenna, but the electric size of the radiator is much larger. The antenna designed in [19] has the same electric size of the radiator as compared to the presented antenna, but its relative bandwidth is much narrower. ...
A novel method of designing a wideband series-fed circularly polarized (CP) differential antenna by using crossed open slot-pairs is presented in this paper. The near-field distributions and input impedance analyses show that the closely spaced open slot-pairs can radiate as the crossed dipoles and have stable radiating resistance with a compact radiator size. Besides, a wideband half-power phase shifter by using open slot is proposed and utilized to realize CP radiation. The proposed CP antenna is composed of a wide slot-pair and a narrow slot-pair. In the antenna design, the narrow slot-pair is not only excited as a radiator, but also elaborately loaded to provide wideband half-power output and quadrature phase excitation to the wide slot-pair. Both the proposed half-power phase shifter and CP antenna are illustrated by the corresponding equivalent circuits. Based on these analyses, the proposed antenna is designed, fabricated and measured. Compared to the simulated traditionally designed counterpart, 2.1 times wider axial ratio bandwidth is achieved for the proposed antenna. The measured overlapped bandwidth for axial ratio <3 dB and return loss >10 dB is 1.95-3.45 GHz (55.6%). Also, the antenna gain and radiation patterns are measured, which agree well with the simulated results.
... In [9], a 2.4 GHz two-faced slot CP antenna was proposed to realize circular polarization. In [10], two off-center-fed dipoles were proposed to realize a broadband CP antenna. In [11], a CP antenna with rotatable dipole-shaped radiation pattern achieved impedance bandwidth of 2.4-2.51 ...
This research proposes a circularly polarized (CP) single-fed omnidirectional dipole antenna operable in 2.45 GHz frequency for the industrial, scientific, and medical (ISM) radio band applications. The proposed antenna consisted of bisectional dipole core, a pair of quarter-wave baluns, and four diagonally adjoined parasitic braces. The bisectional dipole core was utilized to improve the antenna gain and realize omnidirectional radiation pattern, and the quarter-wave baluns were to symmetrize the current on the bisectional core. The four parasitic braces collectively generated circular polarization. In the study, simulations were conducted using CST Microwave Studio and a prototype antenna fabricated. To validate, experiments were carried out, and simulation and experimental results compared. The finding revealed good agreement between the simulation and experimental results. Essentially, in addition to achieving an antenna gain of 2.07 dBic, the proposed CP single-fed omnidirectional antenna is suited to ISM frequency band applications.
... The total height of the CP antenna with the AMC surface is d + h = 30 mm or 0.082λ 0 . The antenna height of the CP antenna above a PEC reflector is found to be 0.3λ 0 [26], which is dramatically reduced by the use of an AMC surface. The geometric parameters of the CP antenna with the AMC surface are listed in Table 4. ...
A novel artificial magnetic conductor (AMC) surface based on spiral strips is proposed, which consists of 9 × 9 AMC cells. Each AMC cell includes a spiral strip to increase its inductance, thus featuring a wide bandwidth of 42% for ±90° reflection phase. The AMC surface is applied to three planar dipole antennas for lowering the antenna heights, including a linearly polarised (LP) antenna, a dual-polarised (DP) antenna, and a circularly polarised (CP) antenna. It is shown by simulation and experiment that the LP antenna achieves an impedance bandwidth of 40% (0.68-1.02 GHz) for |S 11 | < −15 dB and a gain of 8 dBi, the DP antenna realises an impedance bandwidth of 33% (0.69-0.96 GHz) for |S 11 | < −15 dB, an isolation of 30 dB, and a gain of 8 dBi, and the CP antenna has an overlapped bandwidth of 33% (0.75-1.05 GHz) for |S 11 | < −15 dB and axial ratio <3 dB. The heights of all the three planar antennas are lowered from 0.265-0.3λ 0 to 0.083λ 0 .
... In terms of the radiating element, loop, patch, and ring type antenna have been investigated. Traveling-wave antennas with loop structures usually need a broadband balun or a transformer for impedance matching [14], [15]. Rectangular patch antennas with two degenerate modes have a limited bandwidth for CP operation [16], typically less than 5 % in both impedance and axis ratio (AR) bandwidths. ...
A dual-port, dual-band, and circularly polarized (CP) radio frequency identification (RFID) reader antenna is designed to operate at both ultra-high frequency (UHF) and lower ultra-wideband (UWB) bands for indoor positioning systems. In conjunction with a properly-selected quadruple feed network, a shared aperture using the concept of hybrid mode is utilized for broadening the antenna bandwidth. The concept is demonstrated to achieve a high gain, wideband, and CP operation within a low profile. The measured overlapping 3-dB axis ratio (AR) bandwidth and 10-dB impedance bandwidth for the UHF band ranges from 0.918 to 0.926 GHz with a minimum in-band antenna gain of 9.0 dBic. The measured overlapping 3-dB AR bandwidth and 10-dB impedance bandwidth covers from 3.0 to 5.2 GHz with a minimum in-band gain of 9.0 dBic in the lower UWB band (i.e., 3.1 ~ 4.8 GHz). The gain suppression near the two WLAN bands (i.e., 2.45 GHz and 5.8 GHz) is more than 20 dB. The isolation between two ports is larger than 25 dB over the UHF and lower UWB bands, respectively.
... Such OCFDs are very popular in the amateur radio community. Recently, some researchers use the OCFD to create a 90-degree phase delay and generate circular polarization radiation field for the antenna [31]. But, one of the major problems of the OCFD is that the radiation resistance of the antenna could be very high, thus it is required to use a 4:1 or 6:1 balun transformer to convert the impedance to the feeding port 50 ohms resistance [32]. ...
... It is shown that, by modifying a broadband symmetrical bowtie dipole to an OCFD, the antenna impedance is significantly increased over the desired resonant frequency range. In addition, the impedance for both antennas at the frequencies from 1.1 to 1.2 GHz is also very high (i.e. over 200 Ω), this is due to the anti-resonance of the dipole antenna [31]. The next step is to modify the proposed OCFD to a crossed OCFD by introducing another OCFD. ...
Impedance matching networks for nonlinear devices such as amplifiers and rectifiers are normally very challenging to design, particularly in broadband and multiband devices. A novel concept of designing a
broadband high efficiency rectenna without using matching networks is presented in this paper for the first time. An off-center-fed dipole (OCFD) antenna with relatively high input impedance over a wide frequency
band is proposed. The antenna impedance can be tuned to the desired value and directly provide a conjugate match to the impedance of a rectifier. The received RF power by the antenna can be delivered to the rectifier without using impedance matching networks, thus the proposed rectenna is of simple structure, low cost and compact size. In addition, the rectenna can work well in different operating conditions and using different types of rectifying diodes. A rectenna has been designed and made based on this concept. The measured results have shown that the rectenna is of high power conversion efficiency (over 60%) in two wide bands, which are 0.9–1.1 GHz and 1.8–2.5 GHz respectively (mobile, Wi-Fi and ISM bands). Moreover, by using different diodes, the rectenna could still maintain its wide bandwidth and high efficiency over a wide range of
input power levels (tunable from 0 to 23 dBm) and load values (from 200 to 2000 Ω). It is therefore suitable for high efficiency wireless power transfer or energy harvesting applications. The proposed rectenna is general and simple in structure without the need for a matching network hence is of great significance in many applications.
... Several radiation structures, including slots with different shapes [1], [2], off-center-fed dipole [3], magneto-electric dipole [4], and evolutive crossed dipoles [5] have been presented for improving the CP bandwidths. As a typical design, the elliptic crossed dipole obtains the wide axial ratio (AR) bandwidth of 96.6% [5]. ...
A circularly-polarized (CP) patch array antenna is proposed for ultra-wideband operation by introducing weak-coupling mechanism into feeding network, feeding unit, and radiation structure, respectively. As an example, a wideband 2×2 patch array antenna consists of a weakly-coupled-line four-feed network, a coupled feeding unit, and four weakly-coupled sequentially-rotated symmetric hexagonal patches is designed for verification. Measured results show that the proposed antenna exhibits the 10-dB impedance bandwidth of 98% (2-5.92 GHz), 3-dB axial ratio (AR) bandwidth of 96.3% (2.15-6 GHz), and 3-dB gain variation bandwidth of 82.5% (2.65-5.95 GHz) with the peak gain of 9.5 dBic at 5.15 GHz and the maximum efficiency of 88%. By the weak-coupling method, the design achieves not only the largest CP bandwidth and the symmetric radiation patterns without any beam squint over the whole band, but also the smaller volume of (1.13×1.13×0.15) λ03 (λ0 is the wavelength at 4 GHz) compared with the reported patch array antennas. Therefore, the proposed CP patch array antenna is very promising for modern wireless applications such as WiFi, GNSS, and RFID systems.
A novel wideband circularly polarized (CP) dipole antenna is presented. The proposed antenna is configured with three horizontal layers of an electrical dipole, two parasite Π-strips, and a ground, where the electrical dipole is fed by a vertical microstrip balun, resulting in three CP modes. The 180º rotationally symmetric dipole generates two CP modes in the middle- and high-frequency bands. In order to improve the CP bandwidth, two 180º rotationally symmetric Π-strips are introduced and excite the third CP mode in the low-frequency band. The antenna prototype is fabricated, and the measured results show that the -10 dB impedance bandwidth is 1.63 - 3.98 GHz (83.78%), the 3-dB axial ratio bandwidth (ARBW) is 1.70 - 3.11 GHz (58.63%), the realized gain is 7.34 ± 0.32 dBi, and the average radiation efficiency is 80.61%. As a result, the 1-dB gain bandwidth is overlapped with the ARBW, and the realized gain has a high flatness over the ARBW. Therefore, the proposed antenna is a promising candidate for broadband CP wireless communication system applications.
