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A new type of rat-race coupler, based on electromagnetic bandgap (EBG)-loaded half-mode substrate integrated waveguide (HMSIW) and composite right/left-handed (CRLH) HMSIW, has been proposed and investigated comprehensively. It consists of three sections of EBG-loaded HMSIWs with 90° phase delay and one section of CRLH HMSIW with −90° phase advance. Due to the evanescent-mode of EBG-loaded HMSIW and the backward behavior of the CRLH HMSIW in the left-handed region, the size of such a miniaturized rat-race coupler is reduced about 65.7% in comparison with its conventional counterpart. The rat-race coupler with the central frequency of 5.5 GHz has been designed and fabricated so as to validate our method, and its good performance is demonstrated by both simulated and measured results. [ABSTRACT FROM AUTHOR]

One-directional weakly conditionally stable finite-difference time-domain (WCS-FDTD) method is extended to solve electromagnetic problems in linear dispersive media by virtue of piecewise linear recursive convolution (PLRC) technique. This proposed method provides similar accuracy to PLRC alternating direction implicit (ADI) FDTD approach, yet consumes less computational time and less memory. This proposed method is particularly suitable for solving problems in linear dispersive materials with fine features along two spatial directions. [ABSTRACT FROM PUBLISHER]

In this paper, the application of reflected group delay in the design of the output antenna for a 5.8 GHz magnetron is presented. For a radial direction output magnetron, the external quality factor (Qe) is mainly determined by the output antenna. In order to facilitate the output antenna design, we firstly calculate the cold cavity spectrum and the electric field distribution in the anode cavity by simulation. Then the relation between reflected group delay and external quality factor has been derived through equivalent circuit of the magnetron. Moreover, the required reflected group delay is obtained according to the derivation. And the optimum position of output antenna connecting with vane is determined. The sample magnetron has 49.2% output efficiency in hot cavity test [ABSTRACT FROM AUTHOR]

In this paper, a body-worn planar monopole antenna is proposed for body-centric wireless communications systems (BWCS) working at the frequency around 2.45 GHz. The effect of human body in the near vicinity of the antenna on the antenna performance is also investigated. Based on the body-worn monopole antenna, a simple body-worn MIMO system is developed to improve the capacity of BWCS. The effect of mutual coupling between elements on capacity is also considered. The studies show that the capacity of data transmission is improved when MIMO system is adopted. [ABSTRACT FROM AUTHOR]

In this work we investigate three different artificial ground planes for microstrip antenna design, which are useful for different applications. The three different ground plane configurations studied include: (i) conventional dielectric substrate backed by a perfect conductor; (ii) a loop type of artificial magnetic conductor (AMC); and a spiral-type of AMC. Both the loop and spiral types of AMCs tend to lower the resonant frequency of the microstrip patch antenna (MPA), as compared to that of the dielectric substrate, for the linearly polarized case. However, the spiral AMC can be used to realize circular polarization as well, at a different frequency band, hence, is useful for designing dual-band dual-polarization microstrip antennas. [ABSTRACT FROM AUTHOR]

A novel design of epsilon-negative (ENG) material which can exhibit negative permittivity at two nearby bands is presented in this paper. With the unit shape as an unsealed rectangle frame, the components of this ENG material are two folded wires with different dimensions. Each folded-wire structure can achieve electric resonance at a certain frequency band by appropriately adjusting its dimensions. Its electromagnetic properties are then retrieved to demonstrate that the dual-band electric resonances can be obtained in our sample. With the aid of numerical simulation, the transmission property of the proposed dual-band epsilon-negative material is further investigated. And the result shows that the stop band for each folded wire (permittivity ε < 0) is easily adjusted by changing the designing parameters, without influence on the other nearby resonance frequency. It provides an advancement of dual-band and low mutual coupling resonances design. It is also promising that our approach will be effective to make this kind of dual-band ENG material applied into the areas of reconfigurable antennas and their arrays. [ABSTRACT FROM AUTHOR]

This paper proposes the conception of envelope time reversal (TR). Using different frequencies for signal modulation and demodulation, we give the theoretic derivation of one novel frequencydifference method, which demonstrates excellent TR focusing characteristic for envelope signal. In the following experiment, we carry out envelope TR on 100 MHz, 300 MHz and 500 MHz baseband signals separately. Being consistent with theoretic derivation, the experiment result verifies the feasibility of envelope TR. [ABSTRACT FROM AUTHOR]

Some new and simple correlations have been introduced to predict impact sensitivities of various nitro energetic compounds. The correlations are based on the atomic numbers of C, H, N, O, and other amending factors, which are determined by the effect of the connective positions of groups to impact sensitivity. The predicted impact sensitivities for 196 energetic compounds are compared with the latest empirical computations presented by Keshavarz. Root mean square (rms) of deviation from experimental data is 37 cm, which is lower than that obtained from Keshavarz's computation (44 cm) [25,26]. [ABSTRACT FROM AUTHOR]

A technique is developed for the far field pattern analysis of reflectarrays, which is called 'element-in-array pattern' analysis technique. The technique rigorously takes the effects of mutual coupling between elements and the surrounding array environment into account by extracting the scattered fields of the element aperture in a realistic array configuration. Numerical results validate its accuracy and effectiveness. [ABSTRACT FROM AUTHOR]

In this paper, a memory-reduced (MR) 2-D order-marching time-domain (OMTD) method for uniform waveguides is proposed. The OMTD method uses weighted Laguerre polynomials and Galerkin's testing procedure to eliminate the temporal variables and results in an unconditionally stable scheme. Although the OMTD method may be more efficient than the finite-difference time-domain (FDTD) method with too many time steps to complete a simulation, it has to deal with matrix inversion. To reduce its high computer memory requirements and computational power when analyzing complicated geometries, the divergence theorem is introduced to obtain a more memory-efficient matrix equation. Two waveguide examples are presented to validate the accuracy and efficiency of our algorithm. [ABSTRACT FROM AUTHOR]

In this paper, an extended simplified sub-entire domain (ExSSED) basis function method is presented. Its advantage is that it can further reduce the number of unknowns over the original one. Several numerical examples are given to validate its accuracy. Good agreement between the results using the proposed method and those by the method of moments and original simplified sub-entire domain basis function method is achieved. [ABSTRACT FROM AUTHOR]

A modified composite right/left handed (CRLH) transmission line (TL) is presented. With respect to a conventional CRLH-TL, it is a more accurate model because a pure left handed (LH) cell is not possible due to unavoidable parasitic series inductance and shunt capacitance effects. A 45° differential phase shifter constructed by a modified CRLH-TL and a conventional delay TL is designed and implemented using SMT chip components. The new model is validated by simulation and measurement results. [ABSTRACT FROM AUTHOR]

The power/ground bounce seriously affects circuit performance. Several methods have been used to simulate it. These methods ranged from simple lumped circuit models to full-wave (dynamic) three-dimensional Maxwell equations simulators. In this paper, the method of time-domain full-wave analysis is used to simulate the noise caused by three types of different excited sources in the power distribution networks (PDNs), to research the effect of source types on the noise and to analyze the effect of source property, dielectric materials, and boundary conditions on noise voltage and mutual impedance between ports. [ABSTRACT FROM AUTHOR]

An accurate model of composite right/left handed transmission line (CRLH-TL) is used to design an arbitrary dual-band branch-line coupler (BLC). A pure left handed (LH) cell is not possible due to unavoidable parasitic series inductance and shunt capacitance effects, which are taken into consideration in the accurate model. With respect to a dual-band BLC designed with a conventional model, the coupler designed with the accurate model uses less chip components and achieves perfect performance, which is demonstrated by simulation and measurement results. [ABSTRACT FROM AUTHOR]

A compact ultra-wideband (UWB) bandpass filter is presented by using a modified stepped impedance resonator (SIR) and defected ground structures (DGSs). The modified SIR is to generate multiple-resonant peaks within the UWB passband and tighten the coupling with the feed-lines. Then, the DGSs are to enhance the coupling degree of coupled lines and realize wide stopband. From simulated and measured results, the filter shows good UWB performance, including low insertion loss within the passband, a small group delay variation, and a wide stopband with -20 dB attenuation up to 19.6 GHz. [ABSTRACT FROM AUTHOR]

A compact dual-band stepped impedance bandpass filter with a defected ground structure (DGS) is proposed. The half-wavelength stepped impedance resonator is adopted to result in two tunable passbands. A DGS is constructed under the two coupling stepped impedance resonators to achieve good passband performance. Compact size and high selectivity is realized with the tap input/output coupling structure. For demonstration, one RF filter operating at 2.45 and 5.2 GHz is designed. Simulated and measured results are provided. [ABSTRACT FROM AUTHOR]

A novel ultra-wideband (UWB) bandpass filter is proposed by using a modified stepped impedance resonator (SIR). The modified SIR can generate multiple-resonant peaks within the UWB passband and the feed-lines at the two sides can enhance coupling degree. The proposed filter shows good UWB passband performance with low return loss and flat group delay variation in both simulated and measured results. It has a simple and compact structure. [ABSTRACT FROM AUTHOR]

In a standard Schiffman phase shifter a coupled section and a uniform transmission line are used to give a differential phase shift. In order to achieve a larger bandwidth it is necessary to use tight coupled sections which are difficult to be realized. Further more, a 90° Schiffman phase shifter can hardly be realized with a low permittivity substrate. In this letter a novel Schiffman phase shifter is proposed with a defected microstrip structure. The S-parameters of the proposed structure show that the novel Schiffman phase shifter can achieve a phase shift with a low permittivity substrate and can obtain a 30% bandwidth with a phase error +/- 3 deg. [ABSTRACT FROM AUTHOR]

This paper presents a new method for overcoming the structure curvature influence on the antenna properties and processing of conformal array to produce almost ideal pattern by using pattern reconfigurable technique. Artificial neural network (ANN) models of radiating element and conformal array are also created through measured or simulated data. Once the model is developed, it can be used in the design of conformal array and provide fast answers of the tasks. [ABSTRACT FROM AUTHOR]

A novel dual-band design of planar monopole antenna is presented in this paper. Printed on a dielectric substrate and fed by a 50 Ω microstrip line, a planar monopole antenna is demonstrated to generate two separate resonant modes to cover 2.4/5.2 GHz WLAN (wireless local area network) bands with satisfactory radiation properties. The impedance bandwidths of the proposed antenna are 600 MHz centered at 2.65Hz and 1.15GHz centered at 5.12 GHz for S11 < -10 dB. The parameters which affect the performance of the antenna in terms of its frequency domain characteristics are investigated. [ABSTRACT FROM AUTHOR]

In this paper, one of meshless methods named element-free Galerkin method is firstly employed to analyze electromagnetic scattering problems. Moving least-squares interpolations are used to construct the trial and test functions for the weak form. Numerical studies show that it is working and has good performance in electromagnetic scattering problems computation. [ABSTRACT FROM AUTHOR]

In this paper, the sub-entire domain basis function method and characteristic function (CF) method are used to analyze scattering of large-scale periodic structures. The former can dramatically reduce the number of unknows. To reduce the time for impedance matrix generation, the CF method can be used when the distance between the source function and the testing function positions is big enough. Finally, some simulation examples are given to validate the method. [ABSTRACT FROM AUTHOR]

This paper describes the application of the order-marching time-domain (OMTD) method coupled with the discrete Fourier transform (DFT) to the solution of eigenvalue problems. In the cylindrical coordinate system, the resonant frequencies of the TE01δ modes of a millimeter-wave cylindrical cavity dielectrically loaded at the base are determined. The results obtained with our proposed method are compared to the theoretical solutions and results with the finite-difference time-domain (FDTD) method. [ABSTRACT FROM AUTHOR]

A coplanar waveguide-fed uniplanar multi-folded slot antenna that has impedance bandwidth enough to cover UWB systems is presented. The -10 dB return loss bandwidth of the antenna spans from about 3 GHz to about 11 GHz. Parametric study is presented. Details of the proposed ultra-wideband design are described and simulation results are presented and discussed in this paper. [ABSTRACT FROM AUTHOR]

Novel dual-band and broad-band designs of a slot antenna with a cross-shaped stub are presented in this paper. For dual-band operation, the antenna's operating frequency ratio can be tuned by adjusting size of the cross-shaped stub. When proper design is achieved, the antenna can generate two separate resonant modes to cover 2.4/5.2 GHz (wireless local area network) WLAN bands. The simulated impedance bandwidths of the proposed antenna are 260 MHz centered at 2.44 GHz and 610 MHz centered at 5.36 GHz for S11 < -10 dB. Furthermore, it is found that two separate resonate frequencies can be connected to cover the frequency ranges of the digital communication system, personal communication system, international mobile telecommunication, and 2.4GHz WLAN. The bandwidth of the wideband antenna is 1.49 GHz centered at 2 GHz. Details of the proposed dual-frequency and broad-band designs are described and simulation results are presented and discussed in this paper. [ABSTRACT FROM AUTHOR]

In this paper, we introduce a compact two-dimensional (2-D) complex variable technique with the order-marching time-domain (OMTD) scheme to solve lossy uniform transmission line problems. By applying the complex variable technique to dealing with the partial derivative with respect to wave propagation direction in Maxwell's equations, the spatial attenuation along the propagation direction will be taken into account. Thus, in the heavy loss cases, more accurate results can be obtained as compared with conventional real variable technique. At the same time, the weighted Laguerre polynomials and Galerkin's testing procedure are chosen to treat with the time variable analytically. This OMTD method is free of stability constraint and may be computationally much more efficient than the finite-difference time-domain (FDTD) method with too many time steps to compute the solution. In the numerical example, the proposed method shows its advantage of efficiency and accuracy. [ABSTRACT FROM AUTHOR]

A novel broadband millimeter-wave reflectarray antenna composed of compound-cross-loop elements of variable lengths is proposed. Compared to the conventional single-layer reflectarray elements, the compound-cross-loop elements can realize much larger phase variation range from 0° to 465°, leading to broader bandwidth. Using this technique, a 15°-beam-steering reflectarray operating at 30 GHz is designed. The computed results demonstrate the agreement of the main beam steering with the design requirement, and a 1-dB gain bandwidth close to 25.17% is obtained. The validity of the obtained results is verified by comparing the ones generated by Ansoft High Frequency Structure Simulator (HFSS) with those produced by Ansoft Designer. The antenna is useful for millimeter-wave applications. [ABSTRACT FROM AUTHOR]

Odd-even-mode method is used to analyze the mutual characteristics of a two-element Yagi patch antenna. There are odd-mode and even-mode of a two-element Yagi patch antenna. When the operating frequency of the antenna is at the odd-mode frequency, the radiation pattern is a sum-pattern. When the operating frequency is at the even-mode frequency, the pattern is a difference-pattern. By utilizing this method, a pattern reconfigurable Yagi patch antenna is designed. Simulated and measured results are given. [ABSTRACT FROM AUTHOR]

The frequency-domain transmission-line equations for parallel planar transmission lines are derived in this paper. Such a general formula is very useful in order to analyze the characteristics of arbitrary transmission lines. And the hypothesis, i.e., the existence of non-zero diagonal parameters in the parameter matrix, made by Haase and Mei is validated through a sound theoretic derivation. The nonzero parameter takes into account the effects of discontinuity, radiation and higher modes of the lines. [ABSTRACT FROM AUTHOR]

A single folded-slot antenna with a high impedance ground plane (HIGP) has been successfully designed. Employing the design of experiment (DOE) technique, a well-matched folded-slot antenna has been obtained without any matching networks. At the same time, since the HIGP is utilized between the substrate and the ground as a ‘magnetic conductor’, the radiation efficiency of the antenna has been greatly improved. Electromagnetic simulation shows that the return loss of the antenna near 30 GHz is less than -30dB and the directivity is 8.3 dBi. These properties are much better than traditional GPW-fed slot antennas. [ABSTRACT FROM AUTHOR]

A novel partly shielded-finite ground coplanar waveguide (PS-FGCPW) low pass filter has been designed. The device consists of a PS-FGCPW loaded with metal stubs at periodic positions of the signal line. The width of the metal stubs has a sinusoidal variation as the function of the position along the signal line. By properly choosing the position and dimension of the loaded stubs, a wide stop band, more than four times the pass bandwidth, is obtained through the suppression of spurious frequencies inherent to the distributed structures. The prototype also exhibits very sharp cutoff, very low insertion loss in the passband, slow-wave effect and high isolation performance. [ABSTRACT FROM AUTHOR]

Generalized transmission-line equations for lossless parallel planar transmission lines are derived based on exact electromagnetic theory. The hypothesis, i.e., the existence of non-zero diagonal parameters in the parameter matrix, made by Hasse and Mei is validated through a sound theoretic derivation. These non-zero parameters take into account the effects of discontinuity, radiation and higher modes of the lines. [ABSTRACT FROM AUTHOR]

A new pattern reconfigurable microstrip antenna is presented to demonstrate the capability of beam steering by controlling MEMS switches on/off. Simulated and measured results show that two sets of connection states and four switchable directional quasi-conical beams in different quadrants can be obtained at 8 GHz and the return losses are less than –10 dB. One set of connections provides two quasi-conical half power beams in the first and third quadrants of the upper half space. The second set of connections provides two quasi-conical half power beams in the second and fourth quadrants of the upper half space. [ABSTRACT FROM AUTHOR]

This paper present a generalized transmission-line theory which is useful to describe the local radiation effect along almost arbitrary three-dimensional wire structures. For the generalized transmission-line theory, the mathematical structure of the classical telegrapher equation is preserved, while the coefficients (the per-unit-length parameters) are generalized in order to represent the intrinsic behavior of the wire structure. Essentially, the generalized transmission line equations (GTLEs) is a novel kind of telegrapher equation. The equation coefficients of the generalized transmission line equations (GTLEs) are determined from full-wave numerical solutions in this paper. In comparison with the conventional telegrapher equation, the GTLEs has two additional terms - dependent series voltage and shunt current sources - which represent local radiation effect from discontinuities of the nonuniform transmission-line itself. For the double folded stub microstip structure, the novel 1D-GTLEs whose coefficients are determined by dynamic numerical methods can have broadband frequency characteristics. To the investigated microstrip structure as a band stop filter, the S parameters for a frequency band from 3GHz to 18 GHz can be calculated by using only one group of the 1D-GTLEs is sought for the whole structure with stubs and the model of 2D-GTLEs is validated to be more accurate than that of 1D-GTLEs through numerical experiments in this paper. [ABSTRACT FROM AUTHOR]

The efficacy of pest control of three different oil formulations in multiple low-concentration spray programmes on sweet orange and pummelo were compared with unsprayed and normal farmer-treatments over three years. Phytotoxicity of sprays was assessed in terms of fruit and leafdrop, fruityield and external fruitquality. Trees sprayed with any type of oil had lower pest numbers than unsprayed trees. On sweet orange, the heaviest oil was better than the normal farm practice at controlling chaff scale on fruit and red mite and whitefly on leaves. On pummelo it provided the best control of red mite on leaves. All three oils were as effective as the normal farm practice in control of rust mite on sweet orange fruit and leaves and red mite, rust mite and red scale on pummelo fruit. On sweet orange trees there was no evidence of phytotoxicity, and the external quality of fruit generally improved over time. On pummelo trees, oil sprays were unable to improve the external fruitquality. The number of pummelo per tree was reduced in three of the oil spray schedules in 1995 and one in 1996, but the total weight of fruit harvested per tree was unaffected. [ABSTRACT FROM AUTHOR]