In this paper, we propose a novel compact switchable monopole CPW-fed antenna which has the ability to be used for narrowband as well as UWB applications. A single element antenna to be used for wireless local area network (WLAN) applications is first proposed in this article having overall dimensions of 24×30.5 mm2. The corresponding antenna has been transformed to UWB frequency range just by utilizing two variable capacitors within the designed structure. The proposed small size, variable, low cost as well as low weight antenna with good propagation characteristics performs well in the WLAN as well as in the UWB frequency band. The proposed antennais simulated using Ansoft HFSS, and results are validated in CST Microwave Studio suite. The proposed antenna has also been fabricated, and the measured response is correlated with the simulated ones.
The paper presents the results of observing, in a real time, the process of combustion in air of aluminum nanopowder ignited by laser radiation. The obtained results convincingly evidence the possibility and perspective of visualization of ignition process by means of laser monitor. The video images allow observing the main stages of the combustion process including starting of combustion in the place of laser radiation focusing, spreading of the heat wave and appearance of the second combustion wave. For quantitative analysis of the combustion process, we suggest to analyze the average intensity of images registered by laser monitor.
A pair of broadband double-sided parallel-strip line (DSPSL) to coplanar waveguide (CPW) vertical transitions are presented. The transitions are composed of CPW open end with connected grounds forming two strips of the DSPSL with single via connection. The connected grounds of CPW, which forms top strip of the DSPSL are of two dierent shapes resulting in two transitions (Types 1 & 2). Simulated results for the back-to-back transitions, using the multilayer solver of CST Microwave Studio, show good agreement with the measured ones.
A modified three-way in-phase equal Gysel power divider/combiner (PDC) and a method for implementation this novel three-way Gysel PDC on plane structure are proposed in this article. To obtain accurate values of the line impedance,the derivation of the exact equations is based on even-odd mode analysis. An experimental prototype is realized. The results show that this three-way Gysel PDC has good matching, isolation and magnitude-phase balances with high power handling capabilities.
This paper presents a novel 2D meta-surface wall to increase the isolation between microstrip patch radiators in an antenna array that is operating in the teraherz (THz) band of 139-141 GHz for applications including communications, medical and security screening systems. The meta-surface unit-cell comprises conjoined twin `Y-shape' microstrip structures, which are inter-digitally interleaved together to create the meta-surface wall. The proposed meta-surface wall is free of via holes and defected ground-plane hence easing its fabrication. The meta-surface wall is inserted tightly between the radiating elements to reduce surface wave mutual coupling. For best isolation performance the wall is oriented orthogonal to the patch antennas. The antenna array exhibits a gain of 9.0 dBi with high isolation level of less than -63 dB between transmit and receive antennas in the specified THz-band. The proposed technique achieves mutual coupling suppression of more than 10 dB over a much wider frequency bandwidth (2 GHz) than achieved to date. With the proposed technique the edge-to-edge gap between the transmit and receive patch antennas can be reduced to 2.5 mm. Dimensions of the transmit and receive patch antennas are 5×5 mm2 with ground-plane size of 9×4.25 mm2 when being constructed on a conventional lossy substrate with thickness of 1.6 mm.
This paper presents a CPW-fed UWB band-notched antenna having continuously tunable WiMAX rejection band and fixed WLAN rejection band. As the WLAN frequency band is fixed all over the world, it is made fixed with the use of a newly designed resonator in the radiating patch. As the main problem is that the WiMAX band is different in different countries of the world, between 3 and 4 GHz, it is made continuously tunable by using a novel miniaturized implemented resonator in the partial ground plane with variable capacitors. Altering the values of these capacitors tunes the 3-4 GHz rejection band continuously.
Design and experimental optimization of a 5 cm-diameter electron cyclotron resonance (ECR) Ion Thruster was carried out. The experimental results with the shorten discharge chamber demonstrated that its maximum efficiency, specific impulse, and thrust were 38%, 4300 s, 2.3 mN with the power of 130 W, respectively. The beam current was increased with the increment of the propellant flow rate and screen grid voltage. In addition, the performance of the thruster was associated with the distance of the antenna and screen grid. However, the optimum distance depended on the input microwave power which was about 20 W.
A microstrip patch antenna can be readily installed on any non-planar surface due to its conformal property, and this feature enhances its applicability in many areas. Moreover, in some specific applications, it is desirable and mandatory to provide protection of antenna from the unfriendly surroundings. Therefore, the present work focuses on the antenna with a dielectric cover and analyzes its effect on directivity, gain, and bandwidth at various superstrate air gaps. Two antenna models of single and dual elements are considered here separately, and both are conformal to the cylindrical surface. The antenna parameters are studied under varying superstrate gaps with equal intervals up to a quarter wavelength under fixed cylindrical curvature. It is noted that there is a significant improvement of 6% and 12% in bandwidth at quarter wavelength gap as compared to simple single and dual antenna models without dielectric loading, respectively. Also, both the calculated and measured results show the other important constructive effect of superstrate on the antenna performance.
A compact size (20×21 mm2) planar tri-band electrically small antenna is presented for Wireless ISM, RFID application resonating at 1.57 GHz, 2.47 GHz and 926 MHz. The Proposed structure consists of a dual-slot radiating patch and two split ring structures made using combination of L and U shapes forming a defected ground structure (DGS). Length and width of the planar slot is optimized to get the required frequency bands whereas incorporation of DGS leads to increase in impedance bandwidth. The simulated and measured return losses (S11) of all three frequency bands are greater than 10 dB. Impedance bandwidths of 20 MHz (913-934 MHz), 90 MHz (1.5-1.59 GHz) and 70 MHz (2.43-2.50 GHz) are achieved for the proposed range. The electrically small antenna radiation pattern is omnidirectional, and gains of 0.32 dBi, 1.2 dBi and 1.5 dBi are achieved which makes the antenna suitable for RFID, GPS and WLAN applications.
This paper concerns the analysis of the performance of a Composite Right-/Left-Handed (CRLH) distributed oscillator. In order to increase its output power, a modification of the standard configuration is proposed. The basic idea is to combine the signals from the two output ports of the structure by means of a Wilkinson combiner, so obtaining a single output generator. The power performance of the conventional two output oscillator and the power performance of the new configuration are numerically compared by changing the number of employed transistors. The same procedure is adopted to analyze the amplitude of the higher order harmonics in the generated signals as a function of the number of active elements. On the basis of simulated data an increase of the output power, together with a second harmonic reduction, is expected for the single output oscillator with respect to the standard CRLH topology. Experimental results fully confirm these numerical predictions.
This paper presents two novel bandpass filters using sixteenth mode substrate integrated waveguide (SMSIW) and thirty-second mode SIW (TMSIW) cavities, respectively. The overall size of SMSIW and TMSIW cavities can be reduced by a factor of 15/16 and 31/32 in comparison to the filters designed in the conventional SIW resonator, while keeping almost the same resonant frequency. Based on SMSIW cavity, a first-order filter with the center frequency of 2.45GHz and a transmission zero (TZ) located at the upper-stopband is proposed. The second-order TMSIW cavity filter exhibits one TZ at the lower-stopband and two TZs at the upper-stopband, and it has a better performance of the passband than the former with the same size and center frequency. It also has a wider upper-stopband with suppression of an unwanted harmonic at 7.6GHz. Two intersecting rectangular slots are etched between the two cavities with a smaller angle between them of 30 degrees. The whole size of the filter is 24.2 mm×29.1 mm×0.508 mm. The filters are fabricated in SIW technology, and the frequency response shows good agreement between simulated and measured results.
In recent years, wireless indoor positioning systems have attracted significant research interest. However, maximizing system precision remains challenging, especially for three-dimensional (3D) estimates. In this paper, a novel hybrid approach to resolving this problem is proposed through the development of a multiagent system composed of a Bayesian network and a deep neural network for 3D indoor positioning. The proposed system is based on a combination of the multilateration and fingerprint methods in order to reduce the acquisition region of the received signal strength vectors. In addition, the relationship between the quality of the received signal and the noise level, which is influenced by the increase in the number of access points and the number of persons moving within the environment, is considered by the system. The proposed approach exhibits a better performance than other algorithms with an average positioning error of less than 0.9 m. This result represents a difference of more than 22 cm with respect to the most similar algorithm.
Based on the multi-mode interference effect in the periodic dielectric waveguide, a novel waveguide crossing structure is proposed and analyzed. The structure can achieve crossing connection of three periodic dielectric waveguides at the same position with low crosstalk and relative high transmission coefficient. Based on electromagnetic numerical simulation methods, the proposed crossing structure of three periodic dielectric waveguides is calculated and analyzed in details, and at the optical communication wavelengths near 1.55 μm, crosstalks below 22 dB between the three crossing periodic dielectric waveguides are achieved.
In this paper, a novel ultra-wideband (UWB) power divider with dual notched bands using square ring multiple-mode resonators (SRMMRs) is presented. The characteristics of the proposed SRMMRs are investigated by using even- and odd-mode analysis. Then, the initial UWB performance is achieved by introducing SRMMRs to the basic Wilkinson power divider. Finally, two desired notched bands inside the UWB passband are achieved by embedding a pair of coupled dual-mode stepped impedance resonators (DMSIRs) into the SRMMRs. The central frequencies of the notched bands can be easily controlled by the electrical length of the DMSIRs. To validate the design concept, a novel compact UWB power divider with dual notched bands centered at frequencies of 5.8 GHz and 8.0 GHz is designed and measured. The simulated and measured results indicate that it has a low insertion loss and good return loss performance at all the three ports, and a high isolation between the two output ports across the UWB bandwidth from 3.1 to 10.6 GHz with a small size of 0.46λg×0.69λg, where λg is the guided wavelength at 6.85 GHz.
An omnidirectional antenna array is proposed in this paper. The antenna unit of the array is composed of ten radiation patches and the associated microstrip feeding network. Some gaps between top and back patches are introduced in the antenna to improve matching, ease of feeding and enhance the bandwidth. Microwave experiments and numerical simulations are performed to demonstrate antenna functionalities. The fabricated antenna exhibits a bandwidth of 14% (1-1.15 GHz) for VSWR ≤ 1.5, with a gain around 6 dBi. The results are valuable for the design and evaluation of omnidirectional planar antenna arrays with good impedance matching, which are important for airborne and navigation applications.
This paper discusses the spectrum relation in Multiple-Input-Multiple-Output (MIMO) structures and presents an imaging algorithm for sparse linear MIMO array for short range imaging. This algorithm is available for MIMO array consisted by transmit and receive arrays separated from each other. The wave propagation process is used to interpret the spectrum relation in linear MIMO structures; therefore, the convolution relation of spectrum can be clearly understood. Moreover, the spectrum shift effect in linear MIMO structure with separated transmit and receive arrays is discussed and solved according to the spectrum relation. Above all, the imaging algorithm for sparse linear MIMO structure is presented, and the image performance is demonstrated by simulation results.
A quasi-millimeter electromagnetic wave with the frequency of 22-30 GHz is applied to detect knots and holes in wood samples. It has better spatial resolution while keeping good transmission properties compared to microwave region used in the previous experiments. The images of knots and holes in wood are clearly obtained by analyzing the phase and amplitude of the transmitted wave. And the phase measurement results are all better than amplitude results according to phase values changing much more than amplitude.
A novel miniature microstrip-fed multiband antenna for wireless local area network (WLAN) and X-band satellite communication applications is presented in this paper. The proposed antenna consists of two arc-shaped strips, dual inverted L-shaped parasitic stubs and a partial ground plane. The proposed antenna can excite multi-resonant modes while achieving a compact size of 18×34.5×0.8 mm3. The measurement results show that -10 dB impedance bandwidths are 290 MHz (2.28-2.57 GHz), 1.27 GHz (5.0-6.27 GHz), and 850 MHz (7.11-7.96 GHz), which can cover the entire operation frequencies of WLAN (2.48-2.4835 GHz, 5.15-5.875 GHz) and X-band satellite communication system (7.25-7.75 GHz) applications.
In this paper, a new microstrip balanced-to-balanced diplexer is presented and investigated. The proposed diplexer primarily consists of two balanced bandpass filter paths, and each balanced filter path can be designed independently based on two identical stub-loaded triple-mode resonators. It should be mentioned that no extra matching networks are required at the common balanced input port in the design. For demonstration, a prototype balanced-to-balanced diplexer operating at 2.30 and 2.83 GHz is designed, fabricated and measured with 3-dB fractional bandwidths of 13.0% and 13.4%. Both simulated and measured results are provided in satisfactory agreement.
A very simple design method to embed routing capabilities in classical corrugated filters is presented in this paper. The method is based on the calculation of the heights and lengths of the so-called filters design building blocks, by means of a consecutive and separate extraction of their local reflection coefficients along the device. The proposed technique is proved with a 17th-order Zolotarev-filter whose topology is bent twice so that the input and output ports are in the same plane while preserving the in-line filters behaviour. This new filter allows the possibility of eliminating subsequent bending structures, reducing the insertion loss, weight, and PIM.