Radio wave energy harvesting has become one of the most fascinating fields of research, especially in developing antenna for its front end subsystem. This paper presents the development of a single large aperture antenna for energy harvesting system. Three substrate layers FR4-air-FR4 are employed to increase the antenna gain. Measurement result shows that the proposed antenna is able to obtain gain of about 9.61 dBi at 1.575 GHz (GPS L1 frequency), with low return loss of about -17.12 dB. The achieved bandwidth is about 128 MHz. The antenna characteristic is suitable for energy harvesting application.
A printed multiband multiple input multiple output (MIMO) antenna system is proposed in this paper. The MIMO antenna system is composed of two identical antenna elements which are perpendicular to each other. The defected ground plane with two microstrip lines is introduced to suppress the coupling between the antenna elements. The proposed MIMO system operates at two separated impedance bandwidths of 770 MHz (2.09-2.86 GHz) and 890 MHz (5.05-5.94 GHz) with an overall size of 50 × 50 × 1.59 mm3. The achieved isolation at the lower and higher frequency bands is higher than 20.9 dB and 17.8 dB, respectively. The proposed MIMO antenna system is feasible to be used for time-division long-term-evolution (TD-LTE, 2300-2655 MHz) and wireless local area network 802.11 a/b/g (WLAN, 2.4-2.4835 GHz, 5.15-5.875 GHz) applications.
The paper focuses on design and analysis of hexagon inspired fractal geometry and defected ground plane to evaluate the performance of patch antenna for wireless applications. It also emphasizes increasing the antenna bandwidth by incorporating novel rectangular Defected Ground Surface (DGS) structure with CPW feed. In the proposed work, antenna is simulated and fabricated for wireless applications using FR4 as the substrate, and it covers wide band with high gain. The antenna resonates at frequencies of 3.79 GHz and 5.5 GHz with measured return losses of -25.02 dB and -26.03 dB, respectively, making the proposed antenna suitable for Wi-Fi, cordless phone, wireless devices and wireless sensor networks applications.
The block diagram of a TR (Transmit Receive) module that consists of four channels using a silicon substrate is presented in this paper. The silicon substrate fabricated by microelectronic process has been adopted to increase the interconnect density of module. Several broadband vertical transitions are simulated and optimized by EM simulator. The vertical transition works well from DC to 40 GHz. The insertion loss is less than 1 dB, and the return loss is better than -15 dB in back-to-back configuration. A novel TR module based on the silicon substrate is proposed for its miniaturization and high integration advantages. The module occupies a compact area of 30 mm×20 mm×1.8 mm, and the weight is 1.77 g.
Present paper describes the design, development and evaluation of a wideband, compact Ku-band orthomode transducer (OMT) for SATCOM application. It consists of a square waveguide output section, square waveguide to rectangular waveguide transition, straight waveguide port and an orthogonally coupled port. A tapered waveguide section has been used to couple the orthogonal RF (Radio Frequency) signal to the common port. The designed OMT has a transmit port with frequency band 13.75 GHz-14.5 GHz and a receive port with frequency band 10.95-12.5 GHz. Finite element method based ANSYS's High Frequency Structure Simulator (HFSS) EM software has been used for simulation and optimization of OMT. Measured reflection coefficients of OMT over transmission and reception frequency bands are better than -15 dB and -12 dB, respectively. Designed OMT has port to port isolation better than 45 dB against 30 dB isolation of conventional OMT available in market.
A new approach is presented to reduce the monostatic radar cross section (RCS) of a metal surface. In this approach, called Polarization Cancelation, the polarization of incident wave is rotated by several angles so that the reflected wave becomes zero in direction of incidence. The characteristics and mechanism of the polarization rotation and RCS reduction are investigated. The presented approach is verified by simulation and measurement results.
A seven-band antenna for vehicle-mounted T-BOX with a compact structure is proposed and studied. The proposed antenna is composed of a monopole branch and a ground branch. In addition, a slot is embedded in the monopole branch for bandwidth enhancement. By using 0.25- and 0.5-wavelength modes, the lower band (824-960 MHz) and higher band (1710-2690 MHz) are covered. The working mechanism is analyzed based on S-parameters and surface current distributions. The attractive merits of the proposed antenna are that the structure is compact with a small ground, and no lumped element is used. The measured results show that the antenna can cover the lower band of GSM850/900 and the desired upper band of DCS1800/PCS1900/UMTS2100/LTE2300/2500. The measured efficiencies are also presented.
A circular microstrip antenna (CMSA) cannot be fed directly with 50 Ω microstrip (MS) line, without an inset or an impedance transformer, as all around the periphery the impedance is equally high. The feeding technique such as inset fed or quarter wave transformer makes the antenna geometry asymmetrical. In this paper, a technique using single shorting post and a pair of shorting posts is proposed to match the peripheral impedance of the CMSA with that of the 50 Ω-MS-line feed for operation around 2.45 GHz. The shorting posts perturb the current distribution on the patch, altering the input impedance at the periphery. By selecting proper shorting posts positions a wide range of impedance has been adjusted without altering the patch geometry. Due to symmetric arrangement of the double shorting posts, the proposed antenna configuration has a very low cross-polarization ratio of better than -65 dB at the broadside direction for 2.45 GHz. The simulated results of the directly fed 50 Ω-MS-line CMSAs are experimentally validated with good agreement.
A miniaturized rat-race coupler with arbitrary power division ratio is proposed in this paper. The design formulas of the rat-race coupler with arbitrary power division ratio are derived using the even-odd decomposition analysis. The proposed structure demonstrates miniaturized size and perfect isolation due to adding phase inverter to the branch. For demonstration, a 20 dB rat-race coupler operating at 1 GHz with 81.34% size reduction is designed and fabricated. There is good agreement between measured and simulated results.
We study the electrical conductivity of three-dimensional (3D) nanocomposite with incorporated random carbon nanotubes (CNT). Large length of the remote nanotubes generates a lot of intersections that induce rather small percolating threshold of the global conductivity in this medium. We simulate such a system by random cylinders placed in a percolating parallelepiped with the use of Monte Carlo method. Conductivity of such structure is associated with the critical phenomena, where the main transition parameter is de ned by the value of the percolation threshold. We calculate the minimal percolating threshold and determine the functional form of the conductivity by the global optimization technique. Such an approach allows studying the details of the electrical conductivity in nanocomposites even at signi cant level of the percolating fluctuations.
The main objective of this article is to design, realize and measure the performance of a reconfigurable antenna for wireless applications. The designed antenna will be able to switch among several modes, from the ultra-wideband mode (UWB mode) to narrow band mode (NB mode) and then dual-band mode (Bi-bands mode) and vice versa in order to combine the maximum functionality. By incorporating two resonators into the octagonal antenna, the initial antenna can be covered by one wideband (UWB mode), one narrow sub-band (NB mode), or two narrow sub-bands (Bi-bands mode). The ultra-wideband mode is obtained by deactivating the two resonators (so the antenna operates as a classical octagonal antenna), while the one narrow band mode is obtained by activating just one resonator. In the bi-bands mode, the two resonators are activated at a time to be used as a coupling-bridge to very narrow frequency bands. To present the work, simulated and measured results are given and discussed.
We present a new equal power quadrature branch line coupler (BLC) for dual-band applications in this paper. A new topology of the dual-band quarter wavelength transmission lines (TL) with the derivation of design equations is also introduced. The proposed BLC is designed using Advanced Design System (ADS) and fabricated on Rogers 5870 at 0.9 GHz and 2.4 GHz center frequencies. The design approach for the proposed dual-band BLC is endorsed by the simulated and measured results. A comparative analysis of this BLC with the previous BLCs is also carried out.
The deformation of antenna array due to external factors results in a significant degradation in the performance of the array direction of arrival (DOA) estimation. To solve this problem, an equivalent method based on the estimation of signal parameters by rotational invariance technique (ESPRIT) in single signal source for the array position errors is proposed in this paper. This method is mainly for the low-order deformation of the array and is based on the equivalent value of the position error. The DOA estimation of ESPRIT algorithm for single signal source was corrected. The simulation results show that the position error equivalent method can effectively equalize the position error caused by the vibration deformation of the array. When the equivalent position error is known, the orientation of the single signal source can be effectively corrected.
A frequency tunable multi-layer low cost microwave absorber is proposed for Ku and X bands of applications. The tunability is obtained with the cavity model design using two metallic layers; a frequency selective surface (FSS) layer and a metal backed substrate layer with the air gap between them. The change in air-gap results in variation of the effective substrate height, and as a consequences the resonant frequency is tuned. The coupling of LC resonance and cavity resonance at an air-gap of 7.5 mm results in a dual-band absorption of the design. The proposed absorber performance has been analyzed for both TE and TM polarizations of incident wave, and the results are found to be same. The studies on surface current distribution and incident angle variation are observed to get physical insight behind absorption. The waveguide measurement method is used to correlate the simulated results with the measured one. With this simple cost efficient design, the absorber appears well suited for EMI/ EMC application at X and Ku bands.
A multiple-arm dipoles antenna array based on magnetic coupling is proposed for ultra-high frequency (UHF) radio frequency identification (RFID) near-field applications. The design utilizes four multiple-arm dipoles to form a square region fed by a quarter-wave impedance transformer double-side parallel stripline (QDSPSL) structure. Broadband performance can be obtained for two different resonant frequencies caused by different dipole arm lengths. Moreover, in induction area, stronger and more uniform magnetic field distribution is generated for phases of currents on three dipole arms being kept in the same compared to conventional single-arm dipole. A 170 × 170 × 1.6 mm3 antenna has been fabricated on an FR-4 substrate to fit RFID near-field application. The measured 10-dB impedance bandwidth is 190 MHz (810-1000 MHz), which covers the entire UHF RFID frequency band (860-960 MHz). Measured tests on the antenna read range are carried out, exhibiting a reading region of 100 × 100 mm2 and 100% reading rate within 200 mm for near-field tags.
In this paper, to overcome signal-to-interference-and-noise ratio (SINR) performance degradation in the presence of steering vector (SV) mismatch between beam pointing and desired signal's SVs, we study the mismatch of SV with adaptive uncertainty level. This estimation is derived based on the geometrical interpretation of the mismatch and can be expressed as a simple closed-form expression as a function of the presumed SV and the signal-subspace projection. Then, the adaptive uncertainty algorithm self-adjusts the uncertainty sphere according to the estimated mismatch SV at each iteration. Finally, the robust adaptive sidelobe canceller (R-IASLC) algorithm can accurately evaluate the mismatches between the actual and presumed SVs and improve the target SINR. Simulation results verify the effectiveness of this method.
A dual-band two-element Multiple-Input-Multiple-Output (MIMO) antenna for Wireless Local Area Network (WLAN) applications is proposed in this paper. The MIMO antenna consists of two closely arranged symmetric monopole antennas with edge-to-edge distance of only 5.3 mm (0.044λ at 2.51 GHz). To enhance isolation, a decoupling network is inserted between the two antennas without increasing the footprint. The -10 dB impedance bandwidths in lower and higher frequency bands are 2.46-2.7 GHz and 5.04-5.5 GHz. Compared to previous works, the presented decoupling structure can obtain higher isolation over 30 dB in dual bands. Measured results agree well with the simulated ones.
A new C-band monopole antenna is proposed for use in a CAPS-based vehicle monitoring system. This monopole antenna has highly omnidirectional main beam with low elevation angle and sufficient half-power beamwidth by using a cone-shaped ground plane. The impedance bandwidth defined by 10 dB return loss is 650 MHz (5.50-6.15 GHz), and the main beam elevation angle and the half-power beamwidth are about 20° and 40° at the operating frequency 5.885 GHz, respectively. The manufactured prototype has survived a long-distance terrestrial test across China, and the design requirements for the satellite link budget, volume, cost, etc. have been reached.
This is the first communication reporting a compact broadband printed circular slot antenna with stair shaped ground plane in which bandwidth is enhanced mainly in the lower frequency band on adding 19 strips at regular space intervals in the partial ground plane. The impedance matching at specific band (7.1-8.4 GHz) takes place as a result of circular slot in the patch. The proposed structure is printed on an FR4 substrate with εr = 4.3 and 0.025 loss tangent over a compact volume of 20×25×1.5 mm3. The impedance bandwidth (S11 < -10 dB) of the proposed antenna is 133.7 % (3.0-15.1 GHz). The antenna exhibits 4.9 dB peak gain and 74 % peak radiation efficiency in the operating band. Satisfactory results and such a simple and easy to fabricate design with compact space make the proposed antenna a suitable choice for UWB applications, 5.2/5.8 GHz WLAN bands, 3.5/5.5 GHz Wi-MAX bands, X band (8-12 GHz) and other wireless communication systems. Measured and simulated results are in good agreement, affirming the simulation process. Omnidirectional radiation patterns are generally observed in the operating band of the designed antenna.
A new class of tri-band bandpass filter (BPF) is presented, and harmonic passband bandwidth can be independently controlled. In the implementation, three coupling paths are used to control the bandwidth of each passband. The first coupling path is two grounded vias which are utilized to realize coupling between two short-stub loaded resonators. And the first coupling path delivers signals at the first passband. Meanwhile, the second coupling path delivers signals at both the first and second passbands. And the third coupling path only delivers signals at the third passband. Using this method, both the frequency and bandwidth of each passband can be designed and tuned easily. In this filter design, the first harmonic passband can be adjusted separately and is independent of the fundamental passband. Two grounded vias improve flexibility and form a fundamental passband and harmonic passband independently controllable passband filter. For demonstration, a tri-band BPF with three passbands at 1.5 GHz, 2.5 GHz, and 3.5 GHz with insertion losses of 0.34, 0.76 and 1.08 dB is designed, fabricated and measured. So this proposed filter will be attractive in wireless communication systems.
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