Authors:
Bahare Zaki;Zaker-Hossein Firouzeh;Abolgasem Zeidaabadi-Nezhad;Mojtaba Maddahali;
Pages: 533 - 540 Abstract: Here, two new AMC structures are presented with $180^circ pm 37^circ $180°±37° phase difference in wideband frequency of 4.97–17.15 GHz. Three implementations of two AMC structures are presented, which include periodic checkerboard structure, aperiodic checkerboard structure, and randomised structure. The periodic checkerboard structure is presented in two models. In the first model, the RCS is reduced> 9.6 dB in the frequency range of 9.3–16.9 GHz, which is equivalent to 58.02%. In the second model, the RCS is reduced>7.8 dB in the frequency range of 8.1–16.9 GHz, which is equivalent to 70.4%. The second model is analysed through FMB parameter, bistatic and monostatic RCS. For improving the RCS reduction bandwidth, the new aperiodic checkerboard structure and the optimal randomised structure are presented with bandwidth of 81.67 and 98.69%, respectively. In aperiodic and randomised structure, the reflected field is scattered more uniformly in many direction. Therefore, the 3D bistatic RCS pattern is improved greatly. For validating the result of simulation, the second model of periodic checkerboard structure is fabricated and RCS reduction is measured, which are in good agreement with simulation results. PubDate:
4 17 2019
Issue No:Vol. 13, No. 5 (2019)
Authors:
Igor Ivanchenko;Maksym Khruslov;Nina Popenko;Daniel Rönnow;
Pages: 541 - 545 Abstract: A combined L–S-band antenna module consists of four rectangular patch antennas, two of which operate at the frequencies of the first harmonics (L-band), and two others at the frequencies of the second harmonics (S-band). The module is intended for use in super heterodyne signal reception circuits, for example in studying the various non-linear phenomena. The results of this study are presented in terms of improving the performance of each antenna and minimising their mutual influence. The resonance frequencies of the L-band antenna differ by 50 MHz. All the antennas radiate close to the zenith and their beamwidths in two principal planes are virtually the same. At the resonance frequencies, the reflection coefficient is S11 PubDate:
4 17 2019
Issue No:Vol. 13, No. 5 (2019)
Authors:
Homayoon Oraizi;Amrollah Amini;Amirhosein Shakoori;Mehdi Karimimehr;
Pages: 546 - 553 Abstract: In this study, an analytical method is proposed for design of double-ridged horn (DRH) antenna, which is based on impedance matching of the structure by the method of least squares (MLSs). New basis functions are used for the MLS to obtain optimum impedance functions for the realisation of maximum matching. The resultant reflection coefficients are compared with available methods. The proposed optimum synthesis method is applicable to the arbitrarily tapered DRH antenna with a general cross-section. As two applications, the proposed method is used for the design of linear and non-linear flares of DRH antennas with rectangular and elliptical cross-sections for operation in the frequency band 2–18 GHz. For the proof of concept, a prototype model of the proposed rectangular horn antenna is fabricated and measured in the frequency domain. PubDate:
4 17 2019
Issue No:Vol. 13, No. 5 (2019)
Authors:
Wen Jiang;Kunzhe Zhang;Bo Zhao;Yao Su;Shuxi Gong;
Pages: 554 - 558 Abstract: This study describes a method for designing miniaturised frequency selective rasorbers (FSRs) with a transmission band located between two adjacent absorption bands. The proposed FSR composes of a bandpass frequency selective surface at the bottom and an absorptive surface (APS) with lumped resistors and parallel LC resonators printed on the top. The absorptive surface is a 2.5-dimensional geometry for the purpose of miniaturisation. The mounted parallel LC resonators mounted in the APS are utilised to implement the transmission characteristics of the proposed FSR while the constructed lumped resistors in the APS are used to realise the absorption performance. A prototype is fabricated and measured in an anechoic chamber under the guidance of a free-space measurement system to verify this method. Experiments show that the proposed FSR has a transmission band at the centre frequency of 7.24 GHz and over the bands from 4.85 to 6.82 GHz and from 8.05 to 9.36 GHz, both reflection and transmission coefficients are less than −10 dB. The performances of the proposed FSR with different incident angles and polarisations are also investigated and results show that it is insensitive to electromagnetic wave polarisations and has a stable performance when the incident angles up to 45°. PubDate:
4 17 2019
Issue No:Vol. 13, No. 5 (2019)
Authors:
Qing Liu;Dong-Fang Zhou;De-Wei Zhang;Da-Long Lv;
Pages: 559 - 566 Abstract: Here, three fourth-order bandpass filters (BPFs) in modified box-section schemes using substrate integrated waveguide (SIW) are proposed and researched. The proposed filters are based on a conventional box-section structure with considering bypass/constant/frequency-dependent coupling (FDC) in the diagonal cross-coupling path to construct new filtering responses. Based on the different type of the cross-coupling path, the frequency response of each proposed structure is analysed and presented, which indicates that the proposed filters have flexible response in terms of finite transmission zeros (FTZs). The proposed filters can realise generalised Chebyshev responses with one/two/three FTZs at arbitrary positions. Moreover, one FTZ may be produced by using bypass coupling and direct inductive coupling window to improve lower stopband performance, which is verified by a coupling matrix. For the demonstration, three quasi-elliptic response filters were designed, fabricated, and measured. Good agreement is achieved between simulated and measured results. PubDate:
4 17 2019
Issue No:Vol. 13, No. 5 (2019)
Authors:
Hiromitsu Uchida;Masao Nakashima;Seiichi Handa;Takehiko Sagara;Ken-ichi Hariu;
Pages: 567 - 573 Abstract: A transmission/reflection estimation method based on ‘through-line’ measurements is proposed for N-way tree-shaped power-combining network, mainly used as an output impedance-matching network of a multi-transistor-cell power amplifier (PA). The method can be applied when all the N branches can be seen identical to each other and are excited uniformly in-phase, and especially useful when the input impedance of the network has a non-resistive (reactance) component. In the proposed method, a pair of the N-way networks is connected directly in a back-to-back manner (‘through’ configuration) and with transmission lines in-between (‘line’ configuration), and their S-parameters are measured. The transmission/reflection coefficients of single N-way network can be estimated from the measured ‘through’ and ‘line’ S-parameters, where in the latter the electromagnetic coupling between the transmission lines should be dealt with carefully to avoid estimation error. PubDate:
4 17 2019
Issue No:Vol. 13, No. 5 (2019)
Authors:
Daotie Li;Zhonglin Wu;Jun-Fa Mao;
Pages: 574 - 583 Abstract: Ultra-wideband high-gain dipole antennas are urgently desired for mobile communications. A novel fractal-evolved dipole called modified hexagonal Sierpinski grid carpet dipole, of which size is about 1.5λ in upper band is developed. With self-similarity and periodicity of fractal geometry, the dipole antenna is excellent in performances. It has an ultra-wide bandwidth and high gain, due to a so-called ‘array effect of element antenna’. It presents a gain as high as 12.7 dBi and stable unidirectional radiation patterns within band of 2.0–3.93 GHz (BW = 65.1%). In addition, the dipole also has good cross-polarisation differentiation, high efficiency, high front-to-back-ratio, small size, low-profile (0.156λL), and light weight. A prototype was fabricated from a plastic body by 3D printing technology and then electroplated on the surface. Then, the sample was measured and compared with simulation results, and good agreements are obtained between them. So, correctness and validity of the design methodology are verified successfully. Due to these remarkable advantages, the fractal antenna is attractive to many radio services, such as mobile communications, defence and military, public security, aeronautics and aerospace, and so on. PubDate:
4 17 2019
Issue No:Vol. 13, No. 5 (2019)
Authors:
Wenquan Cao;Xinmeng Lv;Zhiyuan Zeng;Jun Jin;Han Liu;
Pages: 584 - 590 Abstract: Patch-coupling method is adopted to broaden the bandwidth of one dual-band dual-mode dual-circular polarisation (DBDMDCP) circular microstrip antenna in this paper. The function of dual-band dual-mode (DBDM) is excited by simplified metamaterial structure. Curved branches loaded on the ground plane and slots perturbation of radiating patches are used to excite the circular polarisation (CP) property for both n = 0 omnidirectional mode and n = 1 mode unidirectional mode, respectively. By loading four parasitical coplanar coupling patches on the top surface, the impedance of the patch mode is obviously broadened. Furthermore, methods of coplanar coupling and cascade coupling with circular patches are both adopted to broaden the axial ratio (AR) bandwidth maintaining the impedance matching condition. Considering the processing precision, the cascade coupling type is finally fabricated and compared with the probe-fed type for verification. Measurement results show that impedance bandwidths of 4% (centered at 4.52 GHz) and 17% (centered at 5.89 GHz) with maximum gain of 1.0 dBic and 7.1 dBic are realised for the dipole mode and patch mode, respectively. Furthermore, the 3 dB axial ratio (AR) bandwidth of the patch mode is 9.2% (520 MHz centered at 5.66 GHz). Compared with the former designs, this one owns simpler structure, considerable bandwidth besides of pattern and polarisation diversity. PubDate:
4 17 2019
Issue No:Vol. 13, No. 5 (2019)
Authors:
Raafat Lababidi;Maryam Al Shami;Marc Le Roy;Denis Le Jeune;Khaled Khoder;André Pérennec;
Pages: 591 - 596 Abstract: A novel tunable channelised two-branches passive bandstop filter using a reconfigurable parallel-coupled-line-based phase shifter (PS) is presented. The filter topology uses the signal destructive principle and aims to protect the receiver against an unwanted interference signal received by the antenna. The global filter topology contains two branches, each of which has a different function. The bandpass tunable branch selects the frequency to be rejected while the reconfigurable PS plays the signal inverter role. The simultaneous tunabilities of both bandpass and PS branches are ensured by using identical varactor diodes and features 550–700 MHz tuning range. In addition to having a constant and relatively high rejection level over all the tuning range and low insertion loss in the passband area, the filter guaranties ultra-low power consumption. Moreover, synthesis equations are proposed and used to illustrate the operating principle, and finally validated by comparing simulations results to measurements. PubDate:
4 17 2019
Issue No:Vol. 13, No. 5 (2019)
Authors:
Sungjae Oh;Jongseok Bae;Hansik Oh;Wonseob Lim;Youngoo Yang;
Pages: 597 - 601 Abstract: A dynamic supply switching (DSS) modulator using a single-inductor dual-output (SIDO) dc−dc converter for complimentary metal-oxide semiconductor (CMOS) radio frequency (RF) power amplifier (PA) integrated circuits is presented. The DSS modulator consists of the SIDO dc−dc converter and a supply switching circuit (SSC). The SIDO dc−dc converter requires only one off-chip inductor while generating two of the dc voltages. The SSC dynamically switches the high and low dc voltages according to the modulated signal envelope. The supply switching control voltage, which is generated from the envelope, is optimised for maximum efficiency improvement. The proposed DSS PA using the SIDO dc−dc converter and the SSC was fabricated using a 0.18 μm CMOS process for a 1.75 GHz frequency band and a long-term evolution (LTE) application. For the LTE 16-QAM signal with the peak-to-average power ratio (PAPR) of 7.5 dB, the measured efficiency of the DSS PA is 33.8% at the average output power of 21 dBm, thereby satisfying the adjacent channel leakage power ratio (ACLR) level of −30.1 dBc. The measured efficiency of the DSS PA at an average output power of 15 dBm is 24.8%, which is higher than that of the stand-alone PA by 13.3%. PubDate:
4 17 2019
Issue No:Vol. 13, No. 5 (2019)
Authors:
Slawomir Koziel;Adrian Bekasiewicz;
Pages: 602 - 607 Abstract: In this work, the problem of computationally efficient frequency scaling (re-design) of circular polarisation antennas is addressed using surrogate-assisted techniques. The task is challenging and requires the identification of the optimum geometry parameters to enable the operation of the re-designed structure at a selected (required) centre frequency. This involves handling several performance figures such as the antenna gain, the impedance bandwidth, as well as the axial ratio bandwidth. The design technique described here involves two types of surrogate models: an inverse surrogate (utilised to find the initial design) and a forward surrogate of the structure response sensitivities, necessary to realise post-scaling design correction. The entire re-design process is fast and only requires a few full-wave electromagnetic simulations of the antenna. The proposed dimension scaling method is demonstrated using a patch antenna with circular polarisation fed through a branch-line coupler. The structure is re-designed within the operating frequency range of 4.5–6.5 GHz. Numerical results are validated experimentally. PubDate:
4 17 2019
Issue No:Vol. 13, No. 5 (2019)
Authors:
Ankang Liu;Ling Huang;Yilong Lu;
Pages: 608 - 614 Abstract: A wideband circular patch antenna with enhanced omnidirectional gains in the horizontal plane is presented. The gain enhancement over 1 GHz bandwidth is achieved by loading a low-profile ‘I-shaped’ structure (ISS) without increasing antenna's thickness. The effective refractive index of the ISS is larger, over a wide bandwidth than that of the conventional substrate with the same material. Therefore, the artificial structure behaves as a lens to refract the electromagnetic wave which is parallelly incident to the ISS and thus is able to concentrate the energy and enhance the antenna's horizontal radiation performance. In addition, the proposed antenna achieves a relative bandwidth of 19% through combining the resonant frequency for the TM01 mode and another resonant frequency excited by the coupling between the circular patch and the unit cells for verifying the wideband gain enhancement of the ISS. Both simulation and measurement results indicate that the proposed antenna achieves 0.5–2.0 dB gain increment within the operating bandwidth compared with the unloaded antenna on the same ground. PubDate:
4 17 2019
Issue No:Vol. 13, No. 5 (2019)
Authors:
Sandip Nandi;Bijoy Bandyopadhyay;Soumen Khatua;
Pages: 615 - 622 Abstract: Realising the importance of the ionospheric effects on low Earth orbit (LEO) satellite signals, tomographic reconstruction method has been applied to study the relative X- and O-mode power distribution at an altitude of LEO satellites over the low- and mid-latitude regions of the Earth. Eight regions of the ionosphere in Northern and Southern Hemisphere have been reconstructed tomographically based on the Ionex TEC data and direct measurement TEC data over West Bengal, India and subsequently ray tracing of very high frequency waves has been performed. Then, based on the magnetoionic theory, the relative X-mode power distribution has been investigated. Evaluation of the results and observations related to the existence of X-mode only band and narrow O-mode only band ensures the possibility of application of ionospheric tomography technique for study of relative absorption in the ionosphere. The outcome of this research will greatly assists the researchers to interpret the ionospheric effects on radio waves. PubDate:
4 17 2019
Issue No:Vol. 13, No. 5 (2019)
Authors:
Thai Van Trinh;Gyonyun Kim;Jungjin Kim;Chang Won Jung;
Pages: 623 - 630 Abstract: This study presents the implementation of an internal antenna for ultra-high-definition televisions (UHD TVs), which has encountered challenges such as inherently narrow impedance bandwidths, limited space, and the effect of material properties of the TV to the antenna performance. The proposed antenna consists of a pair of rectangular arms (the dipole mode), which are fed by the coaxial cable, these arms are also connected to the ground plane (the loop mode) through two shortings that excite an additional resonance mode. In addition, reconfigurable antennas also offer attractive potential solutions to solve the challenging antenna problems related to narrow bandwidth using the ability to switch and tune operation frequency. Herein, a frequency reconfigurable dipole–loop antenna which can cover the entire ultra-high-frequency band (UHF: 470–771 MHz, BW: 47.4%) is achieved using PIN diodes for switchable frequency and varactor diodes for tunable frequency. A 49-inch UHD TV is used for the practical implementation experiment. The TV bezel (ԑr = 3.5, tanδ = 0.005) is used as the substrate for the antenna design. The designed antenna for UHD TV applications achieves good impedance matching and stable radiation characteristics in the UHF band, considering S11 = − 6 dB (VSWR 3:1) as the impedance matching criterion. PubDate:
4 17 2019
Issue No:Vol. 13, No. 5 (2019)
Authors:
Sangeetha Subbaraj;Padmathilagam Sambandam;Malathi Kanagasabai;Mohammed Gulam Nabi Alsath;Sandeep Kumar Palaniswamy;Indhumathi Kulandhaisamy;Saffrine Kingsly;Yogeshwari Panneer Selvam;Deepa Thangarasu;
Pages: 631 - 641 Abstract: In this study, a multiband 8-element MIMO antenna operating at LTE 800/2300/2500 MHz, GSM 850/900/1900 MHz, UMTS, DCS, PCS, IMT, WLAN 2400 MHz, WiMAX 3500 MHz and Wi-Fi 5800 MHz is proposed for handheld devices. The proposed antenna comprises of radiating elements and novel decoupling structure to reduce the mutual coupling. To obtain multiple resonances, F-shaped monopole, C-shaped strips, L and S-shaped monopoles are integrated to form the complete radiator. The protruded ground plane with inverted π-shaped slot acts as the decoupling element. The eight elements are arranged in a certain fashion to achieve spatial and polarisation diversity. The impedance bandwidth achieved is 170, 1070, 400 and 700 MHz. The isolation is>20 dB in all the desired operating bands. The simulated peak gain and efficiency of the antenna at the four operating bands are 4.8/6.3/5.4/4.7 dBi and 75/90/80/83%, respectively. Furthermore, the envelope correlation coefficient, the apparent diversity gain and effective diversity gain are calculated and presented. The obtained measured and simulated results are in good correlation with each other. PubDate:
4 17 2019
Issue No:Vol. 13, No. 5 (2019)
Authors:
Jayendra Kumar;Banani Basu;Fazal Ahmed Talukdar;Arnab Nandi;
Pages: 642 - 648 Abstract: In this study, a multiband frequency reconfigurable antenna is presented. The proposed antenna can switch among fixed GSM850/900 MHz, LTE1600/1700/1800 MHz and ISM2400 MHz bands through switchable, single, three double, and two triple band modes. The multiband operation is obtained using a spline-based radiator and two open-ended rectangular slot-resonators (RSRs). Three series configurations of PIN diode radio-frequency (RF) switches are integrated into RSRs to activate and deactivate it. The position of RSRs and RF switches is precisely optimised to obtain the desired operating bands and the input scattering parameter (S11) below −10 dB. RF switches #1–3 are turned ON and OFF to transfigure the current distributions on the radiator resulting in the frequency band-switching operation. It is shown that the integration of RSRs and PIN diode RF switches into the antenna structure degrades the radiation efficiency. To improve the radiation efficiency, the antenna is fabricated on a low dielectric constant multilayered substrate built using RT/Duroid 5880 laminates and an air gap. The increased multiband operation, good radiation efficiency, omnidirectional radiation pattern, and sufficient co-cross polarisation isolation are obtained in all operating bands. The prototype of the antenna is fabricated and fairly good agreement is seen amongst simulated and measured results. PubDate:
4 17 2019
Issue No:Vol. 13, No. 5 (2019)
Authors:
Yougen Xu;Yulin Huang;Junfeng Liu;Zhiwen Liu;
Pages: 649 - 659 Abstract: In widely linear beamforming, the second-order non-circularity property exhibited by the signal-of-interest (SOI) can be exploited to improve interference and noise suppression. Assuming known SOI steering vector and spatially white noise, several algebraic schemes for estimating the SOI non-circularity coefficient are proposed in the context of narrowband widely linear beamforming without training/reference signal. These new estimators are based on signal purification, pseudoinverse, oblique projection, and pre-processed subspace separation. Simulation results are included to illustrate the performances of the proposed methods. PubDate:
4 17 2019
Issue No:Vol. 13, No. 5 (2019)
Authors:
Emad Elrifai;Marjorie Grzeskowiak;Gaëlle Lissorgues;Frédérique Deshours;Christophe Bourcier;Gérard Carrer;Elodie Richalot;Odile Picon;
Pages: 660 - 665 Abstract: This study presents the design, fabrication, and measurement of a square open-loop resonator (SOLR) on high resistivity silicon substrate feed with a planar Goubau line (PGL), which is a very low-loss transmission line around 60 GHz fabricated through a very simple and low-cost process. Electromagnetic simulations using ANSYS high frequency structure simulator are performed for the PGL structure, in order to determine the PGL characteristics (impedance, losses and quality factor) versus the line width. The geometrical parameters of the SOLR structure are studied to observe their impact on reflection and transmission properties. An equivalent lumped element circuit is extracted from the distributed planar design to study and optimise the resonating structure using Advanced Design System. This electrical circuit response is successfully compared to the planar electromagnetic structure one, and a parametric study permits to better understand the role of the different circuit elements. Field displays lead to a better understanding of the SOLR behaviour. For measurement purpose of the fabricated structure, a coplanar waveguide-PGL transition is optimised with 0.9 dB losses. Simulation and measurement results show good performances for filter applications with 1 dB losses and small size at 60 GHz for 10% bandwidth. PubDate:
4 17 2019
Issue No:Vol. 13, No. 5 (2019)
Authors:
Noemen Ammar;Henri Baudrand;
Pages: 666 - 674 Abstract: In this study, the wave concept iterative process method is developed in a spherical coordinate system in order to investigate the characteristic of multiple-loop antennas around a multilayer sphere. The analysis method is based on the incoming and outgoing waves defined from the tangential electromagnetic fields at the interfaces of the layers. The iterative process is governed by two systems of equations linking the waves in spectral and spatial domains. The toggling between the two domains is insured by the Legendre transformation. Numerical results consider single and multiple loops (both activated and parasitic loops) around a metallic sphere coated by one or several dielectric layers. The mutual coupling and the radiation characteristic of a loop excited by two feeding sources are analysed. The influence of parasitic loops on the return loss of the activated loop is extensively investigated including the number and the position of the loops on the sphere. The coupling sensitivity between two activated feeding sources is also investigated. The presented results agree very well with the simulation and the literature. PubDate:
4 17 2019
Issue No:Vol. 13, No. 5 (2019)
Authors:
Ahmed S. Eltrass;Nahla A. Elborae;
Pages: 683 - 691 Abstract: In this work, a new design of wide-band multiple-input multiple-output (MIMO) antenna with improved isolation and dual-band rejection is proposed for wireless systems operating over the entire ultra-wide-band (UWB), X-band, and Ku-band (3–18 GHz). The proposed four-element UWB-MIMO antenna is fabricated on Rogers RT/Duroid-5880 substrate with dimension of 73 × 73 × 0.79 mm3. It achieves high isolation (>20 dB) between antenna elements without using any decoupling structures. In order to prevent interference problems from nearby WiMAX (3.3–3.8 GHz) and WLAN (5.1–5.8 GHz) systems, a C-shaped stub is embedded in the radiating patch and a pair of U-shaped parasitic strips is inserted beside the feed line in the single element design. The effectiveness of the proposed design is demonstrated by investigating measurement and simulation results, and comparing them with other existing designs. The results show that the proposed design has an input reflection coefficient PubDate:
4 17 2019
Issue No:Vol. 13, No. 5 (2019)
Authors:
Senshen Deng;Feng Xu;Peng Chu;Ke Wu;
Pages: 692 - 698 Abstract: Two kinds of classical triangular metric resonant cavities including the isosceles right triangular and equilateral triangular metric cavities are investigated carefully. A comprehensive and rigorous derivation process of these two resonant cavities is proposed. Based on this, the mode function and the transverse field components for the modes in the triangular substrate-integrated waveguide (SIW) cavities can be provided. Then the resonant frequency of both kinds of triangular SIW cavities can be calculated. Combined it with the coupling matrix, a fourth-degree filter implemented of isosceles right triangular SIW cavities and a sixth-degree filter formed by equilateral triangular SIW cavities are designed, fabricated and measured in detail. The measured results are in line with the simulated ones. The frequency responses of both filters show a pair of transmission zeroes at each side of the pass band due to the cross-coupling structure. It also verifies the validity of the derivation in this study. Compared with the rectangular and circular resonant ones, the construct of the triangular cavity has the advantage of much more compact. Besides, the proposed filters based on the triangular cavity also have their own advantages of low cost, good selectivity and easy integration with other planar circuits. PubDate:
4 17 2019
Issue No:Vol. 13, No. 5 (2019)
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