Thermal hose is capable of transferring the thermal energy of a finite source to arbitrary long distance. This is achieved by using stretching transformation and can be ideally constructed by using a material with a highly anisotropic thermal conductivity. For practical realization, such a thermal hose can be made of homogeneous conductors in bilayer configurations, employing only copper and expanded polystyrene. It is shown that the thermal energy can be well confined and almost perfectly transferred in an arbitrarily bending hose, demonstrating excellent flexibility. More interestingly is that, when a point heat source is placed at the opening of a split-ring-shaped hose, the temperature of the inner region becomes uniform and reaches nearly as high as the heat source. These novel properties of the proposed flexible thermal hose have been numerically validated in time-dependent case, showing excellent transfer and configuration of thermal energy.
A compact wideband antenna consisting of a L-shaped radiating element which has a modified inverted-F structure and a C-shaped parasitic radiating element on the ground is proposed. Three resonant frequencies and a very wide operating band are obtained. A prototype of the proposed antenna has been constructed and experimentally studied. The measured results show that the operating bandwidth with 10 dB return loss is about 2.9 GHz (2.11-5.01 GHz), 81.46%, respectively, covering LTE2500 (2.5-2.69 GHz), 2.4 GHz WLAN and 2.5/3.5 GHz WiMAX bands. Furthermore, the antenna has a simple planar structure and small volume of only 30 × 30 × 1.6 mm3. Good radiation characteristics and acceptable peak gains are obtained over the operating bands.
A novel microstrip diplexer with high selectivity and isolation performance is proposed through the combination of two compact bandpass filters composed of open/shorted lines and an open stub, which are designed for LTE application. Six transmission zeros in the upper stopband are used to suppress the harmonic of the microstrip diplexer. The transmission zeros near the passband can be adjusted conveniently by only changing the electrical length of the open/shorted stubs. A diplexer prototype with two passbands at 1.8 GHz and 2.1 GHz is fabricated. The isolation between the two channels is greater than 40 dB from 0.1 to 6.5 GHz.
An approach of reducing Mutual Coupling between two patch antennas is proposed in this paper. Here, a meander line resonator is placed in between the radiating elements. By inserting the meander line resonator between the patch antennas with the edge-to-edge distance less than λ/18, about 8 dB reduction of Mutual Coupling throughout the 10-dB bandwidth has been achieved without degrading the radiation pattern.The circuit model of the proposed configuration is carried out in this paper and envelope correlation coefficient is also computed. The proposed structure has been fabricated and measured.
A 3D printed dual-ridged horn antenna (DRHA) is presented. The antenna design is optimized for additive manufacturing and is 3D printed using acrylonitrile butadiene styrene (ABS) and then painted with nickel based aerosol spray. The coaxial transition is also included in the 3D printed prototype. The antenna was manufactured with the intention of improving learning and education of electromagnetism and antennas for undergraduate students using a low-cost personal desktop 3D printer. The painted DRHA has a 10 dB return-loss bandwidth of 6621 MHz (1905 MHz-8526 MHz) with a peak gain of 11 dBi. This prototype is the first known ABS based horn antenna with the coaxial transition embedded into it.
A novel feeding network is investigated both theoretically and experimentally. The proposed system with combination of a Wilkinson power divider and two branch-Line couplers is established. The output signals of the system have the same amplitude and 900 phase difference with each other. The size reduction technique is applied to minimize the physical size of the proposed network. In this technique, the ground of the structure is defected, and distributed capacitors and inductors are added to empty space of the branch-line couplers. Moreover, meandered lines are used in order to match the output impedance of the Wilkinson power divider arms and reduce its size. The initial design realized in 2.5 GHz shows the fractional bandwidth of 24%. Then a miniaturized structure is fabricated with 42% smaller size than the main structure while it shows similar electrical performance. For both cases, measurement and simulation results are in good agreement with each other.
This paper presents the use of micro-electromechanical systems (MEMS) switches to realize the radiation pattern reconfiguration of microstrip antenna, which works in Ka-band. The antenna was fabricated on a silicon substrate and designed to reconfigure radiation pattern at the operation frequency of 35 GHz. The simulation results show that by controlling the states of MEMS switches between the driven element and two parasitic elements, the antenna can achieve reconfigure into three maximum radiation directions in the H-plane (θ=0°, ψ=90°, θ=14°, ψ=90°, and θ=-14°, ψ=90°, respectively). The measured maximum radiation directions of modes-1, modes-2, modes-3, modes-4 are θ=17°, -25°, 3.5°,0.7° and gains of four modes at the maximum radiation direction are 5.78 dBi, 6.49 dBi, 7.24 dBi, 6.31 dBi, respectively. The measured results are closely consistent with the simulation ones. The proposed antenna can be applied to satellite communication.
A compact broadband bandpass filter (BPF) on Composite right/left-handed (CRLH) Quarter-Mode Substrate Integrated Waveguide (QMSIW) is presented and analyzed in this paper. A size reduction is implemented by etching the CRLH interdigital slots (CRLH-IS) in the compact QMSIW cavity to introduce a lower resonant frequency less than that of the QMSIW. The influence of the rotation angle of the CRLH-IS on the frequency response of the CRLH QMSIW BPF is analyzed, and the optimal rotation angle is used to implement a BPF with good out-band rejection. The proposed CRLH QMSIW shows the characteristics of low quality factor and high coupling coefficient that make it a good solution to design a broadband bandpass filter. The measured insertion loss is less than 1.8 dB at 4.43 GHz with a fractional bandwidth (FBW) of around 22%. The measured results agree well with the simulated ones.
In this letter, a new design for patch antenna, which can obtain low radar cross section (RCS) and high gain performance simultaneously, is proposed on the basis of a metamaterial (MTM) superstrate. The superstrate consists of two metallic layers with different patterns on both sides of a dielectric substrate. Low reflection and transmission are obtained from the upper surface which can absorb most of the incident wave to reduce the antenna RCS. The bottom surface, which has partial reflectivity, is used to construct a Fabry-Perot resonance cavity with the ground plane of the patch antenna to improve its directivity. Measured results show that the proposed antenna can achieve RCS reduction in a broad frequency band ranging from 2 to 14 GHz with maximum RCS reduction value of 28.3 dB, and high gain performance is enhanced by 4.3 dB at most compared with the original antenna in the working frequency band extending from 10.9 GHz to 12 GHz. The measured results agree well with the simulated ones.
This paper deals with experimental verification of reciprocity relations for nonlinear quadripole, such as Hall transducer. We suppose that the matrix of quadripole resistances can be decomposed into the sum of matrices: linear and nonlinear. We experimentally confirmed the classical reciprocity relations for linear part of matrix of resistances.
A new defected ground structure (DGS) is designed to reduce the mutual coupling of a dual-frequency printed monopole array. The designed dual-frequency DGS consists of two concentric split ring slots. Each split ring slot produces band rejection characteristics at one resonant frequency of the antennas. An effective equivalent circuit model of the DGS section is proposed with the circuit parameters successfully extracted. Good agreement exists among the circuit simulation, EM simulation and experimental results. With the inclusion of the DGS, the measured mutual coupling of the dual-band array has been effectively reduced by 10 dB and 20 dB at two resonant frequencies, respectively.
In this letter, a four-layer transmitarray operating at 9.5 GHz is designed using a double-petal loop element as the unit cell. A configuration of the double-petal loop elements is used to increase transmission phase variation while maintaining a wide transmission magnitude bandwidth of the unit cell, and a full transmission phase range of 360° is achieved for a transmission magnitude equals to or better than -2.4 dB. Furthermore, the oblique performance of the unit cell is also good. Then, a prime-focus 676-element microstrip transmitarray with the proposed element is fabricated and measured. The highest measured gain is about 22.15 dBi at 9.8 GHz, resulting in a 31% aperture efficiency. The antenna bandwidth of 10.2% (from 9.3 to 10.3 GHz) for 1 dB-gain is achieved in this design.
In this paper, a new coplanar waveguide (CPW) fed ultra-wideband (UWB) planar monopole antenna with dual band-reject characteristics is proposed. Two resonators of different lengths are employed at the bottom layer to create two notches at the frequency of interest. The proposed fabricated antenna works from 2.8 to 11.34 GHz with two notched bands which cover the WLAN (5.725-5.825 GHz) and ITU (8.025-8.4 GHz) bands. The proposed antenna is fabricated and measured for verification purposes. Good agreement between the measurement and simulation is found.
A wideband dual-polarized dipole antenna is presented using the differential feed technique. The proposed antenna consists of two horizontal bow-tie dipoles and four vertically oriented meandering strips. Two pairs of differential-fed L-shaped microstrip feed lines are used to excite the antenna. Due to the differential-fed technique, the cross polarization level can be reduced to -35 dB. With the introduction of the meandering strips connecting the radiating patch to the ground plane, the height of the antenna is about 0.102λ0. A parametric study is performed to provide information for designing and optimizing such an antenna. The proposed dipole antenna has been fabricated and measured. The impedance bandwidth of 48.3% (S11 < -10 dB) from 2.57 GHz to 4.21 GHz is achieved. The measured isolation between the feeding ports is better than 30 dB over the operating band. Moreover, the antenna has a compact structure and good unidirectional radiation pattern, making it conveniently integrated with microwave differential circuits and applied in the base station systems.
To reduce the radar cross section (RCS) of a target, plasma coating on perfectly electric conducting plate is studied in this paper. Nonuniform helium plasma produced by a minitype solid rocket engine is with collisional and unmagnetized. Energy excited for generating helium plasma is investigated. Based on the collisional, unmagnetized, and cold plasma model, backscattering RCS is computed by using finite-difference time-domain method. Principle of RCS reduction is explained. To find minimum input energy while RCS reduced, relationship between input power and RCS reduction is discussed, and numerical optimization is also implemented. We can identify optimal parameters and choose the best electron density profile under condition of given input power level.
A novel wide-flare-angle corrugated horn covering the full Ku/Ka satellite communication frequency bands is designed and optimized. In order to satisfy the rigorous bandwidth requirements, a spline-profiled smooth section and a corrugated section with ring-loaded slots are introduced into the wide-flare-angle horn design. Instead of the ``trial-and-error'' method, the Differential Evolution (DE) algorithm is employed to obtain the optimum dimensions of the proposed horn. A prototype of the optimized horn is constructed and measured. Both simulated and measured results show that the proposed horn has good radiation and impedance performance. The performance of the horn is also demonstrated as a feed in a typical dual-reflector antenna. Simulation results show that the overall antenna system meets the usual performance requirements.
A new compact microstrip ultra-wideband (UWB) bandpass filter (BPF) with improved out-of-band rejection and good selectivity is proposed using a modified ring multiple-mode resonator (MMR). The initial UWB bandpass filter comprises interdigital coupled lines and a conventional ring MMR. Then, four high-low impedance resonant cells are periodically placed in the inner area of the conventional ring MMR, which have the properties of achieving harmonic suppression and size reduction. To validate the design theory, a new compact microstrip UWB BPF with improved out-of-band rejection is designed and fabricated. Both simulated and experimental results are provided with good agreement.
This paper presents a very simple comb shaped single layer microstrip patch antenna with seven operating bands for wireless systems. Eight symmetrical rectangular strips are connected by a single strip to achieve multiple operating bands. The proposed antenna provides maximum number of resonating bands compared to the antennas of its class. Effects of additional strips and the connecting strip on the antenna characteristics are studied. A prototype of the antenna is fabricated for experimental validation. The measured reflection coefficient (S11) and radiation patterns are in good agreement with their simulated counterpart. Measured result shows that the proposed antenna can operate at seven different frequency bands 1.56-1.64 GHz, 1.76-1.94 GHz, 3.62-3.74 GHz, 4.43-4.48 GHz, 5.02-5.13 GHz, 5.48-5.62 GHz and 5.92-6.02 GHz. These bands cover some of the most useful bands for wireless systems such as GPS (1570.42-1580.42 MHz), DCS-1800 (1710-1880 MHz), PCS-1900 (1850-1990 MHz), WiMAX and WLAN.
A compact dual-polarized antenna element integrated with balun is proposed. Two pairs of dipoles are employed for the dual-polarizations of the antenna, and strong mutual coupling between them is introduced to widen the bandwidth of the antenna. Bent dipoles are used to reduce the size of the antenna. The simulated and measured results show that the proposed antenna can cover the bandwidth ranging from 790 MHz to 960 MHz with VSWR < 1.5 and isolation > 26 dB. The antenna element is also fabricated and tested. The measured results show that the antenna can be a good candidate for the design of European Digital Dividend/CDMA800/GSM900 mobile communication base station antenna.
Coupled resonators are widely used in the design of cross-coupled filters with dual-passband response and the quasi-elliptic function characteristics. In this paper, we will present a dual-band bandpass filter using only couplings between adjacent resonators, i.e. without cross-couplings. The dual-band bandpass filter with passband centre frequencies of 1747 MHz and 1880 MHz respectively is designed and fabricated using microstrip U-shaped resonators. Using coupled resonator pair as a dual-band cluster, a miniaturised structure is achieved as compared to the conventional topology. The measured responses agree closely with the simulations.