Dipole Arms Research Articles

Photoconductive dipole antennas for efficient terahertz receiver

We designed various photoconductive antennas applicable to efficient terahertz (THz) receivers and experimentally investigated their detection characteristics. Three different antennas based on Grischkowsky (H-), I-, and bowtie shapes were fabricated on a 1.2-μm-thick low-temperature GaAs layer that was grown on a semi-insulating GaAs substrate and subsequently attached to extended hemispherical silicon lenses. The experimental results showed different characteristics for detection responsivity and agreed well with the theoretical prediction. Measurements of the peak-to-peak amplitudes of the detected THz photocurrent were approximately 67, 42, and 59nA for the H-shaped, I-shaped, and bowtie-shaped antennas, respectively. The I- and bowtie-shaped antennas provided higher THz detection sensitivities than the H-shaped antenna in the low-frequency region, i.e., below 0.6THz. At a frequency of 0.2THz, the I- and bowtie-shaped antennas offered an approximately 3.6-fold and 6-fold enhancement, respectively, in THz detection sensitivity compared to the H-shaped antenna. The bowtie-shaped antenna produced better peak amplitude and a wider spectral bandwidth than the I-shaped antenna. The observed detection peak frequencies of the I-shaped and bowtie-shaped antennas possessing very long dipole arms indicate that the lowest limit of the frequency detected in a typical THz-TDS using a GaAs photoconductive antenna as emitter/detector is around 0.2THz.

Elliptical Annular Slot Loaded Trapezoidal Dipole Antenna for Band-Notched UWB Applications

In this paper, a semi-elliptical annular slot loaded trapezoidal dipole antenna with band-notched characteristics for UWB applications is designed. A microstrip feedline consisting of multiple feedline sections is used for improving the impedance matching. The band-notched characteristics for WLAN band are achieved by loading the trapezoidal dipole arms with semi-elliptical annular slots. The designed antenna structure has an operating range from 3.5-12.4 GHz(109%) with band-rejection in the frequency range of 5-6 GHz. Nearly omnidirectional patterns are achieved for the designed antenna structure. The designed antenna structure provided an average peak gain of 2.12 dB over the entire frequency range except in the notched band where it reduced to -2.4 dB. The experimental and simulation results are observed to be in good agreement. An improved bandwidth performance with miniaturized dimensions as compared to earlier reported antenna structures is achieved.

Single/Dual-Polarized Infrared Rectenna for Solar Energy Harvesting

Single and dual linearly-polarized receiving mode nanoantennas are designed for solar energy harvesting at 28.3 THz. The infrared rectennas are used to harvest the solar energy and converting it to electrical energy. The proposed infrared rectenna is a thin dipole made of gold and printed on a silicon dioxide substrate. Different shapes of the dipole arms have been investigated for maximum collected energy. The two poles of the dipole have been determined in a rectangular, circular and rhombus shapes. The rectenna dipole is used to concentrate the electromagnetic energy into a small localized area at the inner tips of the gap between the dipole arms. The dimensions of the different dipole shapes are optimized for maximum near electric field intensity at a frequency of 28.3 THz. A Metal Insulator Metal (MIM) diode is incorporated with the nanoantenna dipole to rectify the received energy. The receiving efficiency of the solar energy collector with integrated MIM diode has been investigated. A dual-polarized, four arms, rhombus shaped nanoantenna dipole for solar energy harvesting has been designed and optimized for 28.3 THz applications.

Small scale yielding analysis for a disclination-nucleated Zener-Stroh crack interacting with a circular inclusion

The elastic-plastic fracture behavior of a Zener-Stroh crack nucleated by a wedge disclination dipole interacting with a nearby circular inclusion is investigated. It is known that a disclination is a strong source of internal stresses and energy, one possible way for the relaxation of the stresses can be in the form of an initiated crack. In the current work, the nucleated Zener-Stroh crack is simulated by a series of edge dislocations with distributed dislocation method. The influence of the disclination is accounted through crack surface traction free condition. To improve the analysis accuracy, the Irwin plastic zone correction is employed to evaluate the elastic-plastic fracture behavior at the sharp crack tip. Von Mises yielding criterion is applied in the plastic zone area to judge the yielding occurrence. Numerical results are given to study the influence of the disclination strength, disclination dipole arm as well as material properties on the stress intensity factor (SIF), plastic zone size (PZS), and crack tip opening displacement (CTOD). It is found that the property of the wedge disclination dipole has great effect on the stress field and the elastic-plastic fracture behavior of the Zener-Stroh crack. Either disclination strength or dipole arm increases, the SIF, PZS, and CTOD will increase significantly. For the same disclination, if the nucleated Zener-Stroh crack has a longer crack length, the SIF, PZS, and CTOD could be smaller. For a Zener-Stroh crack nucleated between the inclusion and the disclination dipole, the interaction between the disclination and inclusion greatly influences the elastic-plastic fracture behavior. However, this influence highly depends on material combinations of the two phases.

COMPACT CIRCULARLY POLARIZED CROSSED DIPOLE ANTENNA WITH CHIP INDUCTORS AND SQUARE RINGS LOADING FOR GPS APPLICATIONS

A compact circularly polarized (CP) crossed dipole antenna with chip inductors and square rings loaded for Global Positioning System (GPS) is proposed in this letter. The CP radiation is produced by crossing two dipoles through a 90 ◦ phase delay line of a vacant-quarter printed ring. Four chip inductors inserted in the dipole arms and four square rings loaded at the back of the dipole arms are introduced to obtain a compact dipole size. The plane dimension of the proposed antenna is 28 mm × 28 mm, which can be widely used for GPS handheld devices. Details of the proposed antenna design and results are presented and discussed.

Tri-Band CPW-Fed Stub-Loaded Slot Antenna Design for WLAN/WiMAX Applications

AbstractA novel uniplanar CPW-fed tri-band stub-loaded slot antenna is proposed for wireless local area network (WLAN) and worldwide interoperability for microwave access (WiMAX) applications. Dual resonant modes were effectively excited in the upper band by using two identical pairs of slot stubs and parasitic slots symmetrically along the arms of a traditional CPW-fed slot dipole, achieving a much wider bandwidth. The middle band was realized by the fundamental mode of the slot dipole. To obtain the lower band, two identical inverted-L-shaped open-ended slots were symmetrically etched in the ground plane. A prototype was fabricated and measured, showing that tri-band operation with 10-dB return loss bandwidths of 150 MHz from 2.375 to 2.525 GHz, 725 MHz from 3.075 to 3.8 GHz, and 1.9 GHz from 5.0 to 6.9 GHz has been achieved. Details of the antenna design as well as the measured and simulated results are presented and discussed.

A Reconfigurable Multiband Antenna for RFID and GPS Applications

A C-shaped patches loaded with dipole antenna designed for multiband antenna is proposed. The antenna can be reconfigured as single band at 1.2275 GHz for GPS applications and dual-band frequencies at UHF band (850 MHz–930 MHz) and ISM band (2.41 GHz–2.54 GHz) required in RFID applications. The performance of the antenna involves changing the switches to ON or OFF mode by controlling switches. By adjusting the dimension of C-shaped patch, a dual-band frequency of 0.89 GHz and 2.46 GHz is performed. The antenna’s gains are 2 dBi and 3.2 dBi for lower and upper bands respectively. The length slot and length of C-shaped patch can be varied to adjust the desired upper frequency as well as the bandwidth. Moreover, the lower frequency can be tuned by varying the dipole arms for both elements. Nevertheless, the dipole antenna operated as single band when the switches are OFF at frequency resonance is 1.2275 GHz with 2.06 dBi of gain. The total efficiency for single and dual band is greater than 90 %. The design methodology and antenna measurement results are both presented and discussed in this paper. DOI: http://dx.doi.org/10.5755/j01.eee.21.6.13760

Slim planar composite antenna with two orthogonal polarisations for WLAN router applications

A slim planar composite antenna for WLAN router applications is presented. A J-antenna and a dipole antenna are proposed as components antennas for the vertical and the horizontal polarisations, respectively. The arms of the dipole adopt a bent structure for size miniaturisation. For tuning the impedance matching, a matching stub is introduced working as a parallel inductor on the upper part of the dipole. The antenna is made by copper and fed by coaxial lines. The final antenna achieves two orthogonal polarisations with a low cross-polarisation level <−18 dB, a return loss better than 10 dB, and port isolation in excess of 19.3 dB from 2.38 to 2.51 GHz, thus making it suitable for use in 2.45 GHz WLAN router polarisation diversity applications. The slim planar structure with 25.5 mm width and light weight makes it easy to install on WLAN routers.

A Compact Multiband Printed Dipole Antenna Loaded With Two Unequal Parallel NRI-TL Metamaterial Unit Cells

A negative-refractive-index transmission-line (NRI-TL) metamaterial-loaded dipole antenna is proposed, which has a fully printed configuration and exhibits multiband performance. The antenna consists of a conventional dipole antenna loaded with two unequal parallel NRI-TL metamaterial unit cells which have the same electrical length, but each is loaded with a thin inductive strip that has a different length and therefore a different effective shunt inductance. An equivalent circuit is extracted to investigate the performance of the proposed metamaterial-loaded dipole antenna by modeling each of the dipole arms as a transmission line. This circuit is then used to verify that the resonant behavior of the proposed antenna can be altered by simply adjusting the lengths of the thin inductive strips. A fabricated prototype has compact dimensions of $40 \mathrm{mm} \times 10 \mathrm{mm}\times 1.6 \mathrm{mm}$ , and exhibits good agreement between the measured and simulated results.

Compact Printed Dipole Antenna for L- Band Radar Applications

This paper presents the design and analysis of a compact microstirp fed wide band printed dipole antenna operating in L band. The dipole antenna bandwidth is improved by flaring of dipole arms, tapering ground plane, and the best impedance matching is achieved by introducing an open circuited stub with dipole arm. Parametric study is carried out to study the effect of dipole length and arm width on the antenna resonant frequency and bandwidth has also been investigated. The antenna is printed on FR4 substrate and the simulated return loss bandwidth is validated by the measured result. The fabricated antenna provides a wide bandwidth of 51.2% at the centre frequency of 1.3 GHz and the peak gain of 3.2 dB which is suitable for phased array radar applications.

A novel fractal for improving efficiency and its application in LTE mobile antennas

ABSTRACTIn this article, we apply a novel fractal in arms of an antipodal dipole for antenna miniaturization that uses the Chu's sphere very effectively to keep antenna efficiency very high in comparison with its counterparts like Koch dipole/monopole. Then, a formula is extracted to determine the first resonance of the dipole. We used this method to design a mobile antenna at LTE13 band (746–787 MHz) which is well known for leading the size of a common dipole antenna to be very large for a handheld mobile. The proposed design shows 40% size reduction in comparison with a common dipole while antenna efficiency is better than 79.28% with S11 greater than 10 dB. It also covers LTE band2 (1850–1990 MHz) with S11 and efficiency better than 6 dB and 78.91%, respectively. The overall size of the printed antenna is 62 × 115 × 1.6 mm3. The simulation and measurement results verify the presented calculations very well. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:2429–2434, 2015

A NEW CLASS OF COMPACT LINEAR PRINTED ANTENNAS

A new miniaturization methodology suitable for printed linear antennas is presented. Miniaturization is accomplished by replacing a linear radiator element of a conventional antenna with a compact continuously varying-impedance profile governed by a truncated Fourier series. A design example of a printed half-wavelength dipole antenna is designed and realized in microstrip technology. The performance of the proposed antenna is compared with its equivalent uniform dipole to highlight the performance equivalency. With a 25% reduction in the dipole arm length, both antennas show a measured peak gain and a fractional bandwidth of 5.4 dBi and 16%, respectively at 2.5 GHz; hence, the overall electrical performance is preserved. It will be shown that the design procedure is systematic and accurate. The proposed approach has potential for achieving advanced frequency characteristics, such as broad- and multi-band antenna responses.

A Compact Circularly Polarized Crossed-Dipole Antenna for an RFID Tag

A compact circularly polarized (CP) crossed-dipole antenna for radio frequency identification in the ultra-high frequency is proposed. The antenna consists of two orthogonal dipoles with an arm composed of a meander line and triangular-shaped ending for achieving a compact size. A modified T-match with a meander line is used for impedance matching between the antenna and the tag chip. In this design, CP excitation is achieved by incorporating two semi-circular curves inserted between the orthogonally arranged dipole arms. The final design, with the dimensions of 35.6 ×35.6 ×0.508 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> , yields a -10-dB impedance bandwidth of 37 MHz (892-929 MHz) and a 3-dB axial-ratio bandwidth of 11.4 MHz (905.2-916.6 MHz). The measured results show that the proposed tag antenna can provide a maximum reading distance of approximately 7.6 m with an effective isotropic radiated power of 3.28 W over the CP operational bandwidth.

종단 정렬된 스트립 쌍 도파기를 가지는 직렬 급전 다이폴 쌍 안테나의 특성 연구

본 논문에서는 종단 정렬된 스트립 쌍 도파기를 가지는 직렬 급전 다이폴 쌍 (series-fed dipole pair; SDP) 안테나의 특성에 관하여 연구하였다. 제안된 SDP 안테나는 두 개의 서로 다른 길이의 스트립 다이폴 안테나와 접지 반사기가 코플래너 스트립 (coplanar strip; CPS) 선로로 연결되어 있다. 두 번째 다이폴 위쪽에 추가된 스트립 쌍 도파기는 두 개의 직사각형 모양의 스트립이며 두 번째 다이폴의 양팔의 종단에 정렬되어 있다. 종단 정렬된 스트립 쌍 도파기의 길이와 폭에 따른 안테나의 특성 변화를 분석하여 대역폭 향상을 위한 최적의 설계 변수를 얻었다. 최적화된 SDP 안테나를 FR4 기판 상에 제작하고 특성을 실험한 결과 전압 정재파비(voltage standing wave ratio; VSWR)가 2 이하인 대역은 1.65-2.93GHz이고, 대역폭이 기존 SDP 안테나에 비해 증가함을 확인하였다. In this paper, the characteristics of a series-fed dipole pair antenna with an end-aligned strip pair director are studied. In the proposed SDP antenna, two strip dipole antennas with different lengths and a ground reflector are connected trough a coplanar stripline. The strip pair director placed above the second dipole element are two rectangular-shaped strips and is aligned at the ends of the two arms of the second dipole. The variations on the antenna performance for different lengths and widths of the director are analyzed, and optimal design parameters for the enhancement of the bandwidth are obtained. The optimized SDP antenna is fabricated on an FR4 substrate, and the experimental results show that the antenna has a frequency band of 1.65-2.95 GHz for a VSWR < 2, which shows enhanced bandwidth compared to the conventional SDP antenna.

A Corrugated Printed Dipole Antenna With Equal Beamwidths

A corrugated printed dipole antenna with equal beamwidths in the principal planes is proposed, designed, and evaluated. Orthogonal stubs are added to the dipole arms to equalize its radiation patterns. They also reduce the size of the dipole arms. The antenna is designed to operate at 3 GHz, and has dimension of 36 × 80 × 1.58 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> . The -10 dB S 11 bandwidth of the antenna is from 2.75 to 3.62 GHz, i.e., 27.3%. The E- and H-plane radiation patterns of the antenna are nearly equal up to 135 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">°</sup> from the boresight. To confirm the simulation results, the antenna is fabricated and tested, showing good agreement between simulation and measurement results. Its performance as a feed on a deep reflector, with f/D = 0.25 and D = 45 cm is also studied, where f is the focal length of the reflector and D is its diameter. It provides an enhanced bandwidth of 29.6%, equal E- and H-plane radiation patterns of the reflector, and a gain of 21.4 dBi or an efficiency of 69%. The reflector is only 4.5 λ0 in diameter and would suffer significant blockage losses with conventional waveguide feeds. The proposed feed causes negligible blockage, and provides a respectable efficiency. It is a suitable feed for small symmetric reflectors.

Multi‐narrowband‐reconfigurable slot dipole antenna

ABSTRACTA new reconfigurable multiband antenna is presented. The antenna operates in triple band and can be switched to operate either in single or dual band. The multifrequency band is achieved by using slots dipole antenna fed by a coplanar waveguide (CPW). Six switches are used and positioned at specific locations in the slots to achieve frequency reconfigurability. The antenna reconfiguration is realized when the dipole arms are coupled or decoupled from the slot edges. Three different sub‐band frequencies (2.40, 3.50, and/or 5.20 GHz) are obtained. Measured and simulated results are presented. The proposed antenna may be suitable for future multimode applications such as cognitive radio systems. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:735–740, 2014

Miniaturized Dual-Band Antenna for Implantable Wireless Communications

A miniaturized dual-band antenna is presented for implantable wireless communications. By introducing an offset at the feedpoint, dual-band performance of a dipole antenna is realized, operating at both Medical Implant Communications Service (MICS) 402-405 MHz and Industrial, Scientific, and Medical (ISM) 2.40-2.48 GHz bands. Parylene-C of thickness 20 μm is taken as a biocompatible insulating layer, and a rather compact size of 67.8 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> (10.02 mm × 10.02 mm × 0.675 mm) is obtained. In order to achieve good impedance matching at the feedpoint, an inductive loop is loaded at one of the dipole arms. The measured |S <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sub> | in skin-mimicking gel shows that a bandwidth of 47.5% and 31.6% can be achieved at the MICS and ISM bands, respectively.

Suppression of Cross-Polarization of the Microstrip Integrated Balun-Fed Printed Dipole Antenna

The high cross-polarization of the microstrip integrated balun-fed printed dipole antenna cannot meet the demands of many engineering applications. This kind of antennas has high cross-polarization levels (about −20 dB). And we find that the high cross-polarization radiation is mainly produced by the microstrip integrated balun rather than the dipole itself. The very limited method to lower the cross-polarization level of this kind of antennas is to reduce the substrate thickness. In this paper, to improve the low cross-polarized performance, firstly, an equivalent model is presented to analyze the cross-polarization radiation. Secondly, a novel structure with low cross-polarization is proposed. The microstrip integrated balun is enclosed by a center slotted cavity. The E-field of the microstrip integrated balun is transformed parallel to the dipole arms by the slot, so the radiation of the cross-polarized component is suppressed. Measured results show that this structure can achieve a bandwidth wider than 40% while reducing the cross-polarization level to less than −35 dB within the frequency band.

Wide-Beam Circularly Polarized Crossed Scythe-Shaped Dipoles for Global Navigation Satellite Systems

This paper describes composite cavity-backed crossed scythe-shaped dipoles with wide-beam circularly polarized (CP) radiation for use in Global Navigation Satellite Systems. Each branch of the dipole arm contains a meander line, with the end shaped like a scythe to achieve a significant reduction in the size of the radiator. For dual-band operation, each dipole arm is divided into two branches of different lengths. The dipoles are crossed through a 90° phase delay line of a vacant-quarter printed ring to achieve CP radiation. The crossed dipoles are incorporated with a cavity-backed reflector to make the CP radiation unidirectional and to improve the CP radiation beamwidth. The proposed antennas have broad impedance matching and 3-dB axial ratio bandwidths, as well as right-hand CP radiation with a wide-beamwidth and high front-to-back ratio.

Multi-Band, Wide-Beam, Circularly Polarized, Crossed, Asymmetrically Barbed Dipole Antennas for GPS Applications

This communication presents a multi-band, circularly polarized (CP), wide beamwidth, highly efficient antenna for use in global positioning systems (GPS). The primary radiating elements are two crossed printed dipoles, which incorporate a 90° phase delay line realized with a vacant-quarter printed ring to produce the CP radiation and broadband impedance matching. To achieve multiple resonances, each dipole arm is divided into four branches with different lengths, and a printed inductor with a barbed end is inserted in each branch to reduce the radiator size. An inverted, pyramidal, cavity-backed reflector is incorporated with the crossed dipoles to produce a unidirectional radiation pattern with a wide 3-dB axial ratio (AR) beamwidth and a high front-to-back ratio. The multi-band antennas have broad impedance matching and 3-dB AR bandwidths, which cover the GPS L1-L5 bands.