A novel hierarchical characteristic basis function method (HCBFM) is proposed to calculate monostatic radar cross section based on singular value decomposition characteristic basis function method. In order to reduce the number of incident plane waves and accelerate the generation of characteristic basis functions (CBFs), an improved CBFs construction method is studied in this paper. Firstly, the target is partitioned with hierarchical approach, and at each incident plane wave, the high-level CBFs defined in large blocks are expressed as a linear combination of the previously generated low-level CBFs defined in the corresponding small blocks. Finally, the high-level CBFs in large blocks are orthogonalized by using singular value decomposition at multiple excitations, and a set of linearly independent CBFs can be obtained. Numerical results are given to demonstrate the accuracy and high efficiency of the proposed method.
In this work, we simulate the electromagnetic field of a rectangular waveguide with side holes. The Helmholtz equations for a given waveguide and dispersion equations are solved. As a result of numerical calculations, the obtained numerical values build the dependence of the modulus of the effective impedance on the wavelength for different types of waves.
A dual-band balun with inherent impedance transformation is presented in this paper. The inherent impedance transformation ratio from a range of 0.4 to 4.0 makes the balun ideal for the on-chip fabrication. The proposed dual-band balun exhibits excellent input port matching, equal output signal with phase di erence of 180, and extremely good isolation and matching at the output ports. A table is provided with the design parameters at the extreme impedance transformation ratios. The design concept of the proposed balun has been validated through a prototype fabricated on a Rogers RO5880 substrate. The measurement results are in good agreement with the EM simulation measurements.
This paper presents a CPW-fed dual-band dual-sense circularly polarized square slot antenna (CPSSA). The antenna consists of a rectangular radiator with two unequal rectangular strips, connected by a CPW feed line. An inverted L-shaped grounded stub is placed in the right side of the slotted ground plane with the orthogonal direction of the feed line to create CP modes. The proposed antenna obtained two CP bandwidths of 3.30-3.78 GHz and 5.40-5.86 GHz with axial ratio (AR) value less than 3 dB, and both the CP bands are overlapped by impedance bandwidth (IBW) of the antenna, ranging from 2.72 to 7.34 GHz. Total size of the proposed antenna is 50×50×1.58 mm3. The antenna is fabricated on an FR4-epoxy substrate and measured. Simulation results are verified by measurement for the given antenna. The designed antenna is well used for WiMAX (3.5 GHz and 5.5 GHz) band with CP characteristics. Design procedures of the antenna are discussed in details for further understanding of the antenna design. Parametric study has been done for describing the mechanism of the dual-band CP with the analysis of electric current distribution of the antenna. Meanwhile, wide axial ratio bandwidth has been obtained in both the bands using this structure compared to other published structures.
A composite right/left-handed (CRLH) half mode substrate integrated waveguide (HMSIW) based leaky wave antenna (LWA) is designed and analyzed in this paper. Equivalent circuit of the unit cell is extracted, and the CRLH performance is clarified. Two HMSIW structures are placed back-to-back to obtain low cross-polarization performance, which is further validated by differential excitation principle. The presented LWA is demonstrated to be a balanced structure with a beam scanning range from -60° to +31°. Besides, less than 1.7 dBi gain variation in the working band (46% centered at 13 GHz) is obtained. Simulated and measured results agree well as experiment shows.
In this paper, we theoretically investigate the electromagnetic response of the widely used layered stacked structure. For a causality and lossy system, For a causality and lossy system, relationships between maximum values of reflection and transmission coefficients are demonstrated, which are related with many parameters, such as absolute bandwidth, layers thicknesses and real parts of the static permittivity and static permeability. Different polarizations and incident conditions are discussed. The results can provide a criterion to judge different designs operating at different spectrum ranges with different thicknesses and materials by comparing them with achievable physical limits.
An impedance synthesis problem of 2D antenna arrays consisting of slotted spherical radiators, whose geometric centers are located at nodes of a flat rectangular grid with double periodicity, has been solved. The problem is formulated as follows: to determine complex impedances distributed over surfaces of the spherical radiators which allows us to steer the radiation pattern (RP) of the antenna array to given directions. Analytical solution of the impedance synthesis problem (as an alternative to numerical solution) was obtained under the assumption that spherical radiators are excited by axially symmetric magnetic currents with equal amplitudes. The approach was verified by simulation of the five-element linear antenna array. The possibility of RP scanning in a wide range was confirmed by using the synthesized distributions of complex impedances.
A novel C-L-L π-type feeding network is presented to tune the working frequency and impedance matching of antenna. Two varactors are used in the tunable feeding network as tunable elements for antenna resonating frequency and impedance matching tuning. The tunable capability of the network is studied, and a patch antenna is used to verify the tunable feeding network. The tunable feeding network is designed, fabricated and measured. The measurement results show that the patch antenna can be tuned from 630 MHz to 1.04 GHz with a maximum impedance bandwidth of 24 MHz of S11 less than -10 dB.
This paper aims to estimate the shape of microwave scattering objects using linear sampling method (LSM) with multifrequency data. LSM is a simple, reliable linear inverse algorithm and uses multiview multistatic single frequency scattered field data measured around target objects. Despite its simplicity and computational effectiveness, the output LSM results depend on the frequency of operation. To improve the LSM performance, the present work proposes a new formulation that incorporates frequency information in the LSM equation. As a result, LSM finds the target's shape by a simple solution to a linear inverse problem via multifrequency data. The output results are tested with various types of numerical examples of synthetic data as well as experimental data provided by the Institute of Fresnel.
A compact wideband filtering power divider is presented in this paper, by using coupled transmission lines at two output ports to realize filtering function. The return loss and insertion loss of the design in the passband are improved by inserting fan-shaped open stubs and etching a T-shaped slot at the input port. The central frequency of the power divider is 2.4 GHz. The measured results show a 10-dB fractional bandwidth of 60%, and a wideband filtering response can be obtained. The material object is designed by using FR4, and the size is 0.4λg*0.2λg. The design is well used in the WiFi band.
This paper presents an exact expression for the mutual impedance of two coaxial loops located on the surface of a conductive ground. The semi-infinite complete integral representation for the impedance is first converted into a finite integral. Then the spherical Hankel function contained in the integrand is expanded according to Gegenbauer addition theorem. This makes it possible to perform analytical integration and express the mutual impedance as a sum of products of spherical Bessel functions. Since no simplifying assumption is introduced in the mathematical derivation, the obtained formula is valid in quasi-static as well as non-quasi-static frequency ranges. Numerical examples show how, accuracy being equal, the proposed expression is less computationally expensive than standard Gauss-Kronrod numerical integration technique.
In this work, we propose a compact CMOS power amplifier using a differentially coupled series inductor for motion detection radar applications. The proposed switching-mode power amplifier is designed with a cascode and differential structure. To realize a compact size matching network, a differentially coupled series inductor is used in the input matching network. In the proposed power amplifier, two typical spiral series inductors for the input matching network are replaced with a single differentially coupled series inductor. As a result, the used chip area of the differentially coupled series inductor is smaller than half that of a typical inductor for the given inductances of each inductor. Additionally, to obtain a high gain characteristic, we adapt modified mode-locking techniques for the power stage of the power amplifier. To verify the feasibility of the power amplifier, we design a 9.5-GHz power amplifier with a 130-nm RFCMOS process. We obtain saturation power of 15 dBm while the power-added efficiency is approximately 28%.
This paper presents the design of a continuous polyharmonic-tuned mode (CPHTM) power amplifier (PA) with an introduced optimal knee voltage waveform control parameter in a continuous harmonic-tuned voltage waveform equation. The optimal knee voltage waveform control parameter works in unison with derived equations, providing bandwidth and efficiency potentials over the limiting factors of the conventional harmonic-tuned power amplifiers (PAs). The effectiveness of the design strategy is proven by the realisation of a CPHTM type-I (CPHTMT-I) PA as compared with a non-continuous polyharmonic-tuned mode type-II (NCPHTMT-II) PA. Test results with continuous-wave (CW) signals show drain efficiency (DE) levels within 53.6%-79% (1.31-2.39 GHz) with 58.4% fractional bandwidth for CPHTMT-I and 64%-78% (1.65-1.95 GHz) with 16.7% fractional bandwidth for NCPHTMT-II. The CW result evidently shows the validation and efficacy of the proposed theory.
Crosstalk is one of the bottlenecks in improving the speed and density of high-speed interconnection systems. In this paper, multi-way and 2-level transmission is changed to one-way and multi-level transmission. Under the condition to maintain the data transmission capacity of the system, the number of microstrip lines is reduced, and the distance between microstrip lines is increased to reduce crosstalk. The simulation results show that over 50% of crosstalk is suppressed in multilevel signal transmission systems.
This article was removed from the website on September 9, 2019, because it has been found to violate plagiarism rule of our journal.
A compact dual-band metamaterial-inspired antenna is designed and developed in this paper. This design is carried out by loading a radial stub (acts as virtual ground plane) onto a circular microstrip fed patch antenna. Proposed antenna resonates at two frequencies fc1 = 2.70 GHz and fc2 = 7.34 GHz with -10 dB simulated impedance bandwidth of 6.6% (2.62-2.80 GHz) and 14.57% (6.57-7.65 GHz) respectively. First band is due to the metamaterial transmission line while second band is due to the coupling between microstrip feed and ground plane. Electrical size of the proposed antenna is 0.27λ0 × 0.27λ0 × 0.014λ00, where λ0 is the free space wavelength at f0 = 2.70 GHz. In addition, this antenna provides antenna gain of 1.49 dB at 2.70 GHz and 3.75 dB at 7.34 GHz in the boresight direction. This antenna also provides dipolar type pattern in the xz plane whereas omnidirectional pattern in the yz plane with cross polarization level of -32 dB in the lower band while cross polarization level of -23 dB is maintained even in higher band. Proposed antenna's compactness, excellent radiation characteristics and ease of fabrication make it feasible to be utilized for Worldwide interoperability for microwave access (WiMAX) and satellite TV applications.
An algorithm called MUSIC-like algorithm was originally proposed as an alternative method to the MUltiple SIgnal Classi cation (MUSIC) algorithm in order to circumvent requirement on subspace segregation. The relaxation parameter β, which was introduced into the formulation of the MUSIC-like algorithm, has enabled the algorithm to achieve high resolution performance comparable to the MUSIC algorithm without requiring explicit estimation of the signal and noise subspaces. An adaptive framework for the MUSIC-like algorithm was later developed under the α-stable distributed noise environment. In spite of great improvement on target's resolvability performance, a trade-off between such improvement and the estimation bias is inherent. In this letter, two novel directional adaptive β-selection methods for MUSIC-like algorithm under α-stable distributed noise are proposed. The proposed methods aim at reducing estimation bias and noise sensitivity which are inherent in prior adaptive β framework. Simulation results highlight noticeable reduction on the estimation bias as well as the noise sensitivity of the proposed methods without excessive compromise on target's resolvability performance compared with the original adaptive β framework.
The aim of this paper is to introduce a new kind of reflectarray cell with both amplitude and phase control abilities. A slot is added in the ground of an arbitrary conventional cell for this purpose. A slotted cell having a square patch is investigated to verify the effectiveness of the proposed approach. This cell is used to reduce the side lobe level of a reflectarray antenna.
A new miniaturized microstrip branch-line coupler with good harmonic suppression is proposed in this paper. The new structure has two significant advantages, which not only effectively reduces the occupied area to 19.1% of the conventional branch-line coupler at 0.90 GHz, but also has high 7th harmonic suppression performance. The measured results indicate that a fractional bandwidth of more than 15.6% has been achieved while the phase difference between S21 and S31 is within 90° ± 0.8°. The measured fractional bandwidths of |S21| and |S31| within 3 ± 0.3 dB are 16.1% and 16.7%, respectively. Furthermore, the measured insertion loss is comparable to that of a conventional branch-line coupler. The new coupler can be easily implemented by using the standard printed-circuit-board etching processes and is very useful for wireless communication systems.
Old susceptibility data, measured in superconducting materials at low-frequency, are shown to be accounted for consistently within the framework of a recently published [1] analysis of the skin effect. Their main merit is to emphasize the significance of the skin-depth measurements, performed just beneath the critical temperature Tc, in order to disprove an assumption, which thwarted any understanding of the skin-depth data, achieved so far by conventional high-frequency methods, so that those data might, from now on, give access to the temperature dependence of the concentration of superconducting electrons.
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