A slim tri-port antenna with polarization diversity and pattern diversity characteristics is presented for 2.45 GHz WLAN router applications. By compositing a J-pole antenna and two perpendicularly crossed dipoles, the proposed antenna achieves available vertical and horizontal polarizations covering the whole horizontal plane. Besides, the two crossed dipoles generate two orthogonal radiation patterns, making it an attractive solution for pattern diversity applications. The three antennas are integrated by sharing the bottom structure of J-pole antenna and the top structure of dipoles, resulting in a slim and compact structure. The proposed antenna is made by copper, with overall volume of only 25.5×25.5×126.5 mm3. Measure results show that return losses of three ports are all better than 10 dB and isolations between each two ports are better than 20 dB from 2.39 GHz to 2.49 GHz. Besides, simple structure, slim size, and light weight make it easy to install vertically on the WLAN routers.
A modified technique to design directional ultra-wideband (UWB) antenna with slotted ground structure approach on the ground plane has been presented for applications in C- and X-bands. Initially, elliptical slot is inserted into ground and thereafter, the axis of ellipse is rotated 45 degrees in direction of the substrate. Minor axis of the ellipse is optimized to locate it symmetrically around the circular patch in order to obtain the full C- and X-band operations and also to enhance directivity. Thereafter, for further improvement in the directivity as well as gain, an elliptical slot in circular patch has also been introduced. The impedance bandwidth approximates about 95% covering the frequency ranging from 4.18-11.50 GHz. The return losses (S11) are -38 dB and -43 dB through simulation, which are -24 dB and -32 dB by measurement at 6.3 GHz, 9.3 GHz resonant frequencies, respectively. Simulated gain and half power beam width (HPBW) are 2.5-8.4 dB and 49-22 degrees in 4.18-11.50 GHz band, respectively. Gain and half power beam width (HPBW) of the proposed antenna improves by 1-2 dB and 5-10 degrees, respectively compared with previously designed antennas. Simulation of the antenna has been carried out on Computer Simulation Technology (CST) software on an FR-4 substrate having dielectric constant 4.3 of thickness 1.6 mm. The measured results show good agreement with equivalent circuit model and CST simulation.
A novel miniaturized single-feed cross-aperture coupled circularly polarized (CP) microstrip patch antenna loaded by four identical shorting strips is proposed and discussed. Each shorting strip underneath the edges of the radiating patch is connected to the ground plane via an array of three identical and equidistant shorting pins. With the assistance of the capacitance offered by the radiating patch and the shorting strips, and the inductance induced by the shorting pins, the patch size and overall size of the proposed antenna have been significantly reduced by 75% and 69%, respectively, compared with the conventional antenna. An antenna prototype with an overall size of 50 mm×50 mm×7.548 mm (0.317λ0×0.317λ0×0.048λ0) and a patch size of 29.43 mm×27.85 mm (0.186λ0×0.176λ0) has been fabricated and measured, which shows a measured 10-dB return loss bandwidth of 92 MHz (4.76%) from 1.886 to 1.978 GHz with a maximum right-handed CP (RHCP) gain of 4.9 dBic. The measured 3-dB axial ratio (AR) bandwidth is 28 MHz (1.46%) from 1.899 to 1.927 GHz with a 3-dB AR beamwidth of more than 140º across the operating bandwidth.
In this paper a new method to solve the microwave matching problem of MEMS shunt connected switches is proposed, as an extension of a previously presented approach based on the image parameter formulation. The image phase concept is used to impose the matching condition in the ``on'' state of the device, which is the most critical one. Two different configurations are investigated: a single basic cell and double basic cell topologies. For both of them an analytic modeling procedure is developed, and the equations for the synthesis of the structures are derived. In order to provide some examples, the method has been applied to a previously realized MEMS shunt variable capacitor.
The paper is devoted to the investigation of electromagnetic field distribution in the vicinity of overhead transmission lines under different environmental conditions, taking into account the wire sag curve in a span. A wire state equation is utilized, which allows one to calculate stresses in the wire and sags based on the known stresses and temperatures in the initial state. The results of the electric and magnetic field distribution on sample 330 kV and 110 kV transmission lines are presented. We show that the highest electromagnetic field levels are associated with the most severe environmental conditions, resulting in the highest sag.
Recent wearable health monitoring systems use multiple biosensors embedded within a wireless device. In order to reliably transmit the desired vital signs in such systems, a new set of antenna design requirements arise. In this paper, we present a flexible, ultra-low profile, and compact dual band antenna. The proposed design is suitable for wearable and flexible telemedicine systems and wireless body area networks (WBANs). The antenna is inkjet printed on a 50.8 μm Polyimide Kapton substrate and fed by a Coplanar Waveguide (CPW). The proposed design has the merits of compactness, light weight, wide bandwidth, high efficiency, and mechanical stability. The performance of the antenna is also characterized against bending and rolling effects to assess its behavior in a realistic setup since it is expected to be rolled on curved surfaces when operated. The antenna is shown to exhibit very low susceptibility to performance degradation when tested against bending effects. Good radiation characteristics, reduced fabrication complexity, cost effectiveness, and excellent physical properties suggest that the proposed design is a feasible candidate for the targeted application.
A magneto-electric dipole antenna with novel feed design with rectangular cavity is proposed, fabricated and analyzed. Due to this new feeding structure, the antenna has been able to achieve wide impedance bandwidth of 68.8% to accommodate various wireless communication applications. The stable peak gain of 10.45 dBi with unidirectional radiation pattern has also been reported for the entire range of operation. The antenna has also been able to achieve low cross polarization levels lower than -30 dB. The antenna exhibits low side lobe radiations and almost identical E plane and H plane radiation patterns in the operating frequency range of 2.0 GHz-4.1 GHz. Due to its good electrical characteristics, the antenna is suitable for various S-band wireless communication applications.
A patch antenna integrated on the cover glass of a commercial space-certified solar cell is examined. Test fixtures were fabricated to study the antenna designed at 4.9 GHz when there was an active solar cell under the antenna. It is found that the solar cell affects the input impedance of the antenna and causes a 2-3 dB gain reduction. Repetitive tests were performed to confirm that the effect from solar cells on the antenna remained the same regardless of the working status of the solar cell, type of cover glass, or the assembly of the solar panel.
In this paper, we present a new computationally efficient method for direction-of-arrival (DOA) estimation in uniform linear arrays (ULAs). A sparse uniform linear array (SULA) structure is firstly extracted from the conventional ULA to exploit its advantage in high resolution. By performing the multiple signal classification (MUSIC), the noise subspace of the SULA is simultaneously orthogonal to the steering vectors corresponding to the true DOAs and several virtual DOAs, where all the true and virtual DOAs for each source are uniformly distributed in the sine domain. Then we divide the total angular field into several small sectors and search over an arbitrary sector. Finally, the true DOAs can be distinguished by the noise subspace of the original ULA. Since the proposed method involves a limited spectral search and a reduced-dimension noise subspace, hence it is quite computationally efficient. Simulation results are provided to verify the effectiveness of the proposed method in terms of computational complexity, estimation accuracy, and resolution performance.
Recently, the RF/microwave electronic technology evolved with the consideration of plastic and organic substrates. Such a technology offers two-folded benefits: in one side for lowering the fabrication cost and in another side for the possibility to bend electronic devices. Such a technology is particularly interesting for the implementation of antenna system. This paper is dealing with the design of flexible microstrip antenna 1:2 array. Theoretical approach on the typically symmetrical antenna 1:2 array is proposed. The design methodology of microstrip antenna combined with 1:2 T-power divider (T-PWD) is described. Based on the transmission line theory, the S-parameter model of the antenna system with non-standard reference load is established. Then, the microstrip antenna passive system is theoretical analysed in function of the physical dimensions of the designed structure. The feasibility of the flexible antenna passive system is investigated with the proof-of-concept (POC) designed on Kapton substrate. The POC prototype consisted of microstrip antenna 1:2 array is designed to operate at about 5.8 GHz. Comparisons between the full wave simulated and measured return losses were performed. Then, simulated radiation pattern highlights the efficiency of the fabricated prototype of passive antenna array.
The electromagnetic passive localization without the need of carrying any device, named device-free passive localization (DFPL) technique, is an emerging technology for determining an uncooperative target's position. The DFPL technique detects the shadowed links in a monitored area and realizes localization with the received signal strength (RSS) measurements of these links. However, most current RSS-based DFPL schemes belong to the model-based DFPL method, since the localization accuracy depends on the shadowing model. Moreover, model-based DFPL methods require high memory and computing resources for accurate tracking performance, and thus may not be suitable for resource-constrained applications. To overcome these problems, in this paper we propose a lightweight DFPL method which makes use of recent link lines detected by wireless sensor networks to estimate the target's location. This method can be independent of the shadowing model and can also reduce the algorithm's storage and computational resource requirements. The effectiveness and robustness of the proposed scheme are demonstrated by experimental results where the proposed algorithm yields substantial improvement for localization performance and complexity.
The aim of this study is to present a dual-band antenna for Wireless Medical Telemetry Service (WMTS) applications. The antenna covers all three frequency bands 608-614 MHz, 1395-1400 MHz, and 1427-1432 MHz, and is intended for continuous health monitoring of patient's vital parameters. The designed antenna consists of a meandered dipole antenna and a superstrate layer to preserve the biocompatibility of the structure. It has a compact size with dimensions 17.6 mm x 12 mm x 2.54 mm. The measured -10 dB bandwidths are found to be 16.3% for the lower frequency band and 10.6% in the upper frequency band. The antenna is in vitro tested in a tissue mimicking solution.
A hybrid algorithm based on the invasive weed optimization (IWO) and the convex optimization (CVX) is proposed for minimizing the peak sidelobe level (PSLL) of linear array with focused and/or shaped beam pattern. In this approach, IWO is adopted to produce the array (described by element positions), and CVX is used to determine the excitations for each produced array. Then the corresponding PSLL acts as the fitness function of IWO to find the optimal positions which lead to the minimum PSLL. Numerical experiments are conducted to validate the effectiveness and robustness of the proposed hybrid approach. Compared with other techniques, a lower PSLL can be achieved with a fixed main beam width or with a shaped main beam using this hybrid algorithm. Moreover, this method can easily cope with some constraints on the aperture, such as the minimum element spacing and the total number of elements.
This paper investigates the performance of a Windowing Based Crest Factor Reduction (CFRWB) technique, to enhance the power efficiency of Radio Frequency (RF) power amplifiers. In particular, CFRWB is implemented on a Doherty Power Amplifier (DPA) in conjunction with Generalized Memory Polynomial (GMPDPD), and Volterra series based Digital Predistortion (VDPD) techniques. Key features like spectral regrowth, Peak to Average Power Ratio (PAPR) reduction, efficiency improvement and Error Vector Magnitude (EVM) have been used to measure the efficacy of the proposed method. Both simulation and experimental results show that the proposed combination of CFRWB technique with GMPDPD and VDPD is able to reduce the PAPR of the complex input signals by nearly 60%, with minimal degrading of the EVM and spectral regrowth. Moreover, such signal with reduced PAPR can be used to overdrive the DPA, allowing for a relevant average efficiency enhancement (i.e., up to 25%), while fulfilling the requirements of modern communication standards such as Wideband Code Division Multiple Access (WCDMA) and long-term evolution (LTE).
In this paper, a Rectangular Dielectric Resonator Antenna (RDRA) with a modified feeding line is designed and investigated at 28 GHz. The modified feed line is designed to excite the DR with relative permittivity of 10 which contributes to a wide bandwidth operation. The proposed single RDRA has been fabricated and mounted on a RT/Duroid 5880 (εr=2.2 and tan δ=0.0009) substrate. The optimized single element has been applied to array structure to improve the gain and achieve the required gain performance. The radiation pattern, impedance bandwidth and gain are simulated and measured accordingly. The number of elements and element spacing are studied for an optimum performance. The proposed antenna obtains a reflection coefficient response from 27.0 GHz to 29.1 GHz which cover the desired frequency band. This makes the proposed antenna achieve 2.1 GHz impedance bandwidth and gain of 12.1 dB. Thus, it has potential for millimeter wave and 5G applications.
Single-layer circularly polarized (CP) reflectarrays in the Ka-band are presented in this paper. Three reflectarray (RA) models are designed and measured, using geometrically dissimilar elements. Each element is analyzed individually and optimized to obtain good performance within the operating frequency band. To compensate the spatial delay from feed to the elements at RA surface, the angular rotation technique has been employed for obtaining reflected phase curve. The performances of the antennas are analyzed at 30 GHz, exhibiting 13.3% of 1.5 dB gain bandwidth, while the axial ratio bandwidth is less than 3 dB in the whole operating band.
A multilayer notch-loaded antenna for dual-band (L & S) operation has been proposed in this paper for wireless communications. The antenna is multilayered with dielectric layers of FR4 and Rogers/Duroid. A superstrate layer has been introduced with square-shaped elements angled at 90 degrees to each other with an empty space just above the patch. The proposed structure of the antenna with superstrate layer is applicable to low frequency consecutive dual band operations. The antenna also shows very good radiation characteristics with a gain of more than 7.0 dB and side lobe levels reduced to a very good extent of around -20 dB.
A compact wideband planar double-sided printed quasi-Yagi antenna is presented. This letter focuses on the feasibility of substituting conventional balun for microstrip-to-slotline transition balun to achieve wider bandwidth and relatively smaller size. The proposed antenna, consisting of a feeding balun, a concave arc-shaped reflector, a modified driver with stacked structure and two directors, is designed and fabricated. Good agreement between simulated and measured results is observed. Simulation and measurement results reveal that the proposed antenna can provide an impedance bandwidth of nearly 100% (2.02-6.05 GHz). Additionally, within the impedance bandwidth, the radiation pattern of the proposed antenna has front-to-back (F/B) ratios ranging from 10.1 dB to 19.1 dB, cross-polarization levels in the main radiation direction from 19.8 dB to 36.2 dB and gains from 3.4 dBi to 7.4 dBi.
The dispersion diagram of infinite periodic structures is useful for the practical design of waveguide filters. Analyzing the pass- and stop-bands (gaps) in the dispersion diagram of a unit cell, it is possible to generate a finite structure with a very similar electrical response. However, the truncation of the infinite periodic structure degrades the pass-band performance. In this paper, these impairments are overcome by means of suitable waveguide tapers matching the impedance of the periodic structure to the access ports. As a result, the analysis and design of practical low-pass filters, derived from passive structures based on Electromagnetic Band-Gap (EBG) waveguides periodically loaded with metal ridges, are successfully addressed. According to these procedures, a five-order and an eight-order EBG low-pass filters are obtained after an optimization step. Measurements of a manufactured prototype fully validate the proposed approach.
This paper presents a new property of maximally-at filter prototype coefficients. The property can be used to relate the summation of all the coefficients to an elegant expression which only includes the first coefficient. This property is then used to calculate the increase in insertion loss of this type of filters in the presence of dissipative losses due to elements/resonators finite quality factors. This presented equation for the excess loss is very convenient and does not require referring to the prototype element value table. The property is also used to show that the group delay of a maximally-at lowpass filter at ω = 0 rad/sec is only a function of the first element value of the prototype filter. Finally, a commercial circuit simulation tool is used to generate examples to verify the accuracy of the presented analytical equations. Additionally, the results are compared to expressions found in classical literature.