A new design of high selectivity wideband bandpass filter based on transversal signal-interaction concepts loaded with open and shorted stubs is proposed in this paper. Two transmission paths are used to realize signal transmission. Path 1 is composed of a T-shaped structure with shorted stub, and Path 2 consists of two open coupled lines loaded with open stubs. A wide five-order passband and high selectivity stopband with four transmission zeros can be achieved in the proposed filter. Finally, a wideband bandpass filter operating at 3 GHz with 3-dB fractional bandwidth of 83.3% (1.55 to 4.05 GHz) is designed, fabricated, and measured. Good agreement between the simulation and experiment is obtained.
This letter presents a compact hexa-mode microstrip resonator which is originated from a traditional stub-load resonator (SLR). Stub in SLR isreplaced by a couple of square-loops in the proposed resonator. The advantage of this replacement is that six modes emerge to realize a compact size, and more transmission zeros are generated in its application on filter to enhance the frequency selectivity. For demonstration, a compact dual-band microstrip filter using the proposed resonator is designed in 2.4 GHz/5.2 GHz of WIFI channel, and six transmission zeros are generated to enhance the frequency selectivity.
Brain stroke is a serious disease and one of the major causes of death. Stroke detection based on the frequently studied microwave imaging method is computation-intensive and not always reliable. This paper presents a stroke-detection scheme based on subspace classification technique. Specifically, the stroke is detected and located using the intersection of the positive antenna lines, i.e. connecting the transmitter and receiver. The numerical results show that the proposed method can detect and locate blood clots efficiently.
This paper presents a short-range imaging algorithm for multiple-input-multiple-output (MIMO) array. One of the steps in a previous method utilizes 2-D STOLT interpolation to transform 3-D data into 2-D data, which is not strict in the view of mathematical derivation and lack of physical meaning. The convolution operation which is analyzed by physical process of angular spectrum propagation is used to explain multi-static configuration and reduce the 3-D data into 2-D ones. This paper gives the physical phenomena of the whole process of imaging. We also explain the different physical meanings of FFT between transmitters and receivers. Numerical simulations show the consequence of STOLT interpolation in the previous algorithm and demonstrate the performance of the proposed algorithm.
In this letter, an interdigital band-pass filter is proposed for out-of-band rejection improvement. Seven quarter-wavelength resonators are employed to form the passband. Three extra transmission zeros (TZs) on both sides of the passband are implemented by introducing source-load coupling and dumbbell defected ground structures (DGS). As demonstrated by the measured results, out-of-band rejection and selectivity are improved by these three TZs, and good performances are achieved. The proposed method of increasing out-of-band rejection is feasible and applicable in the design of modern microstrip filters.
A dual-band microstrip distributed multiplier with two multiplication factors based on the extended composite right- and left-handed (E-CRLH) transmission lines (TLs) is presented. Dual-band operation for distributed multiplier is achieved by three cells, and each cell consists of a transistor, microstrip TL and E-CRLH transmission line. The distributed multiplier exhibits two multiplication factors in two different frequencies: one multiplication factor in reverse direction and the other multiplication factor in forward direction. The excellent agreement between proposed technique and measurement results confirms the accuracy and efficiency of the method.
The paper is devoted to experimental and theoretical study of spectra zone characteristics of the wire medium metamaterial with mechanically tunable unit cell. We experimentally demonstrated the effective control possibility of the spectral characteristics of wire medium metamaterial by varying its elementary unit-cell geometry. We established conditions under which the experimental implementation of the wire medium metamaterial at microwaves possesses the properties of a plasma-like medium and the properties band gap structure. A good agreement between the experiment and theory is demonstrated.
A novel UWB antenna with adjustable rejection bandwidth is proposed and fabricated. The proposed antenna consists of a monopole and a novel dual-T square resonator. The results demonstrate that a wide rejection bandwidth from 10.4 to 11.5 GHz can be achieved, and the rejection bandwidth can be adjusted by transforming the dimensions of dual-T square resonator. Moreover, reflection coefficient curve with two poles at one rejected bandwidth is also obtained which is induced by the proposed novel square resonator. In addition, to explain the mechanism of adjustable rejection bandwidth, the analysis of parametric study and electric field distributions of the design are given. The total volume of the antenna is 27 mm×19 mm×1 mm. Compared to other recent works, a simpler structure, wider rejection bandwidth and more compact size are the key features of the proposed antenna. Owing to its adjustable bandwidth and simple structure, the proposed antenna can be used in UWB communications applications to suppress the radio-frequency interference.
This paper describes the concept and design of a novel compactself-supported cup feedantenna for parabolic reflectors. The feed antenna consists of an open waveguide cup which is excited by a disk loaded dipole. This structure is fed by a coaxial waveguide through a split-coaxial balun and has a rear radiation pattern toward the reflector antenna. Two different types of this configuration are designed in this paper: a linearly-polarized grid reflector antenna fed by a single dipole excitation, and a circularly-polarized solid reflector antenna fed by a cross dipole excitation. The measurement is done for the former, and simulation results of the latter via two different software packages CST and HFSS are compared in this paper. Analyzing the results shows that both types of cup feed antenna have an excellent aperture efficiency and low side lobe level.
A planar wideband balun is proposed. The proposed balun consists of a novel slotline T-junction and three microstrip-slotline transitions. Similar to the principle of the E-plane waveguide T-junction, the slotline T-junction acts as a phase inverter. With the microstrip-slotline transition, the device employs microstrip as feedlines. The radiation loss of the slotline is reduced to improve the insertion loss by loading the slotline with a superstrate and adding via holes along the slotline. An experimental balun with a bandwidth of 128% from 2.2 GHz to 10 GHz is designed, fabricated, and measured for validation. The measured results have reasonable agreement with the simulated ones.
An analytic model is proposed to estimate the electromagnetic field transmission line coupling for both radiated emission and immunity using TEM cell measurements. Further, a coupling impedance is introduced to determine the domination between electric and magnetic fields of the field-line coupling. Comparison of measurement and calculation results confirms the accuracy of the model. The model and coupling impedance can be helpful for the suppression of radiated emission and the enhancement of radiated immunity of transmission lines in electromagnetic compatibility design of electronic systems.
This letter presents a new directional dual-band slotted trapezoidal inverted-F antenna (IFA) for indoor Wireless Local Area Network (WLAN) applications. The dual-band performance can be obtained by tuning the lengths of the inner symmetrical trapezoidal slots and the outer trapezoidal arms in a nearly independent manner. The measured results show that the proposed antenna can provide two separate impedance bandwidths (return loss better than 10 dB) around 180 MHz and 750 MHz for 2.4/5.1-5.8GHz WLAN bands, respectively. Good radiation performance and roughly constant in-band antenna directivities are also observed.
We present a novel type of pixel antennas that are suitable for fabrication in low-cost setups based on commercial inkjet printers. The proposed antennas involve hexagonal cells that can be removed in accordance with rigorous optimizations via genetic algorithms that are supported by full-wave solutions with the multilevel fast multipole algorithm. Optimal pixel configurations are determined precisely for desired electrical characteristics, such as low power-reflection values at required frequencies. Measurements on fabricated samples demonstrate the effectiveness of the optimizations, as well as the favorable characteristics of the hexagonal-cell pixel antennas that fully benefit from the advantages of low-cost inkjet printing.
A miniaturized ultra-wideband (UWB) quasi-self-complementary antenna (QSCA) with band-rejection characteristic is presented and discussed. With the tapered microstrip-fed line and flower-shaped QSC structure, a lower cut-in frequency (3.18 GHz) is obtained with a compact size (9x17.5x1 mm3). By embedding a five-star-shaped ring resonator under the radiation patch, a band-notched feature is achieved. The measured impedance bandwidth below 2:1 VSWR is from 3.18 GHz to 13.4 GHz with a rejection band from 5.45 GHz to 5.95 GHz, and the simulated and measured results of the proposed antenna are in good agreement. Thus, the antenna is suitable to be integrated with the space-limited wireless system without electromagnetic interference at the WLAN (5.47-5.825 GHz) band.
The long-term meteorological data of Era-interim from 1979 to 2014 covering the observation at 00, 06, 12 and 18 have been used to derive vertical refractivity gradient in the lowest 100. Diurnal, seasonal and annual variations of refractivity gradient and its component are analyzed for coastal and plateau areas of Nigeria. The relative frequency of the occurrence of gradient below -100 N-units/km used in clear air propagation study is derived from cumulative distribution of the gradient. Occurrence of anomalous propagation in each region is also estimated. The result will help in the effective wireless link planning and design.
Based on the theory of Babinet's principle, a type of dual-polarized antenna working in C band with complementary structures is designed. The structures comprise a wire loop antenna and a slot loop antenna, which is complemented and fed by a coaxial line. A ground is placed to improve the front-to-back ratio of the antenna. The performance of the antenna is studied numerically and experimentally. A prototype antenna was built, stable and symmetric radiation patterns are obtained within the frequency of 4.9 GHz~5.1 GHz, and the port isolation is less than -24dB. The measured results coincide with the simulated ones. This explains the feasibility of the proposed dual-polarized antenna.
This paper proposes a compact Radial Line Slot Array (RLSA) antenna for 5.8 GHz Wi-Fi devices, which meets market needs. Various small RLSA antenna models with radius of 140 mm, were designed using extreme beamsquint technique. The models then were simulated to result in a best model. A prototype of the best model was then fabricated and measured to verify the simulation. The measured parameters are: a gain of 18 dBi, bandwidth of 1 GHz, beamwidth of 20˚, and mainlobe to sidelobe ratio of 15 dB, which meet antenna specifications for market needs. The prototype was tested as an antenna for a Wireless Fidelity (Wi-Fi) device in order to show its performance. The test showed that the prototype worked properly. Lastly, we compared the size of the prototype with the average size of various antennas available in markets. We found that the prototype had the advantage of small size and flat, with similar performance.
A new compact interdigital capacitor loaded open slot antenna and its lumped model are presented in this letter. Equivalent model analysis shows that the introduction of the interdigital structure increases the capacitive element of the slot and thus reduces the operating frequency of the slot antenna. And the antenna operating frequency as well as its size can be easily reduced by simply increasing the capacitance of the interdigital capacitor and the characteristic impedance of the slot. Experimental results of the exemplary antenna agree well with those of the full-wave simulation, proving that the proposed open slot antenna structure is viable in antenna design.
A clubs-shaped wideband antenna with reconfigurable radiation pattern is proposed. This antenna is composed of two tapered slots of mirror symmetry, embedded with two PIN diodes and fed by a 50 Ω coplanar waveguide (CPW). By controlling states of PIN diodes, two tapered slots can be shut down or opened. Consequently, the proposed antenna works in three radiation modes: one monopole pattern with a simulation frequency band (3.93-5.55 GHz) and two end-fire patterns with an identical band (3.29-6.13 GHz). The antenna is fabricated and tested. Measured results show good agreement with the simulation, which denotes that it is suitable for wideband wireless communication systems.
A new technique for mutual coupling reduction, based on the application of electric resonator, is presented in this paper. In this method, first a custom-designed unitcell is presented that provides a proper S12 response for the mutual coupling reduction, and then, this unitcell is used in a two-element array of wideband dipoles. According to the results, this unitcell provides a maximum reduction of 15 dB in the frequency response of the antenna array while does not have a considerable effect on the reflection coefficient and radiation pattern of the antenna. To verify the results, the antenna is fabricated and measured, and there is a very good agreement between the simulation and measurement.