Main intension is to calculate admittance and radiation pattern of longitudinal shunt slot in rectangular waveguide using Method of Moments (MoM) technique. Resonant length calculation of the slot is a critical parameter in the design of waveguide slot array antenna. All computed results are compared with simulated results. CST Microwave studio is used for the simulation and is totally based on FIT techniques. For computation purpose MATLAB 7.0 is used. The numerical data on transmission and reflection coefficient are evaluated. Method of moment solution is used to calculate resonant length versus slot offset for given waveguide dimension and frequency. E and H field radiation pattern are calculated for different offset in different frequencies.
A set of scalar differential equations for treating scattering by rotationally symmetric radially inhomogeneous anisotropic sphere is presented. These equations may easily be treated by applying the integral equation method that has been developed. Besides a possible different expansion in a Neumann series is also discussed.
A novel compact Archimedean spiral antenna with gaploading is investigated in this paper. A circular frame sharing the same centre with the spiral elements introduces a capacitive gap. By adjusting the width of the gap and the width of the circular frame, the initial resonant frequency of the proposed antenna is shifted from 2.79 to 1.93 GHz. Compared with the traditional Archimedean spiral antenna with the same lowest operation frequency, the area of the proposed antenna can be reduced by more than 30simulated radiation pattern results.
A new structure is proposed for wideband differential phase shifter. The proposed structure consists of a microstrip Nonuniform Transmission Line (NTL) and a microstrip Uniform Transmission Line (UTL). To optimally design the NTL, its strip width is expanded in a truncated Fourier series, firstly. Then, the optimum values of the coefficients of the series are obtained through an optimization approach to have low phase shift error and low reflection coefficient in desired frequency bandwidth. The usefulness of the proposed structure is studied using two examples.
In this paper, we present two pre-processing based techniques in unitary transform-domain for narrow-band interference rejection in CDMA communication systems. In our techniques, by using Karhaunen-Loeve Transform (KLT) and Discrete Fourier Transform (DFT), at the transmitter, eigenvectors occupied by NBI are determined; then the energy of the transmitted signal is set to zero into the direction of those determined vectors. Hence, any information is not deleted by NBI through channel. As a result after applying these transforms, a major part of the processing would be shifted to the transmitter, and thus complexity of receiver is reduced. Our simulation results show that the proposed methods improve the performance of the CDMA communication systems in the presence of narrow-band interference.
The resonant frequency of a microstrip patch (rectangular, square, and circular) changes as soon as an identical patch is brought closer than 0.2λ. Closed form expressions are presented for the E-plane coupled configuration from which this altered resonant frequency may be easily computed. These expressions may be readily used in the computer aided design of microstrip antenna arrays.
In this paper, we model an array of pyramid electromagnetic wave absorbers and calculate the return loss of this array using the FDTD method. For modeling the frequency dependent of the absorber, the Debye model is used. In doing so, a 3 × 3 structure of nine pyramid absorber is chosen instead of the array. The results are compared with capacitance and homogenization methods using average values for ε [10]. The results clearly show that the FDTD is an accurate method for calculating the return loss of an array of pyramid absorbers as compared with three other existing methods, and can be used to simulate the array of pyramid absorbers with different sizes in a wide range of frequencies.
This paper presents the result for antenna factor of microstrip patch antenna when used as electromagnetic interference (EMI) sensor. Antenna factor is an important parameter of a sensor used for EMI measurements. The microstrip antenna has found wide application as transmit and receive antenna in modern microwave systems. In this paper, a new application of microstrip antenna as EMI sensor is presented. The result for antenna factor versus frequency of a microstrip patch antenna is presented using commercial software CST Microwave Studio. Also the experimental results for a prototype antenna are presented and compared with the simulated result.
The scattering of visible light by hexagonal-shaped column containing densely packed inclusions is simulated by a combination of ray-tracing and Monte Carlo techniques. While the ray tracing program takes care of the individual reflection and refraction events at the outer boundary of the particle, the Monte Carlo routine simulates internal scattering processes. A dense-medium light-scattering theory based on the introduction of the static structure factor is used to calculate the phase function for densely packed inclusions. Numerical results of the phase function for a randomly oriented hexagonal-shaped ice crystal with multiple densely packed inclusions are evaluated.
In this paper, a Ku band fan beam reflector back array antenna is introduced. This is made up of two main parts that are planar array and main reflector. The proposed antenna has dimensions of 103.3×27.5×12mm3 including the reflector. This antenna with high gain for incorporating in Ku band radars at 13.4-14 GHz is described. The fan beam radiation patterns with monopolar characteristics i.e., the cross-polarization is at least 10 dB lower than the co-polarization and are obtained in the frequency band of interest. The maximum gain for proposed antenna is 16.6 dBi at 13.75 GHz and the peak gain generally >16 dBi throughout the frequency band of interest.
In this paper, miniature planar UWB filters with circular slots in ground is presented and we are using a new technique by etching a wideband circular-shape slot resonator in the ground plane of the filters. The proposed filters have compact size of 15 × 12.4mm2. Two filters are introduced and the final design achieves flat insertion loss and linear phase of S12 throughout the passband (3.14-8.28 GHz) but occasional slight ripple occurs. Two different results are shown and the minimum insertion loss is less than 0.13 dB for both of presented filters.
Corrugated elliptic waveguide in actually extensive application is analyzed by using the mode matching method and Mathieu function. Considering space harmonics in the interior and higher order modes in the slot region of the corrugated elliptic waveguide, the dispersion equation of even TM modes is derived. The dispersion and attenuation characteristics as well as the influence of passband and stopband properties with the changes of structural parameter are investigated in detail. The calculated results in good agreement with ones in the relevant references are of very important values in theoretical studies and actual applications of corrugated elliptic waveguide for microwave engineering.
An optimal beamformer attempts to increase SNR at the array output by adapting its pattern to minimize some cost function. This is to say that, the cost function is inversely associated with the quality of the signal. Therefore by minimizing the cost function we can maximize signal at the array output. The primary optimal beamforming technique discussed in this paper will be MMSE, LMS, Frequency Domain LMS for GPS multipath reduction. In case of a GPS satellite, the DOA of the desired signal is mathematically known because the position of a satellite in an orbit is fixed at a particular time instant. So in some particular adaptive antenna algorithm the DOA of the desired signal is directly given as input.
Research of antenna Radar Cross Section (RCS) is very important for low observable platform. Aperture coupled microstrip antenna is fit for the low RCS antenna design because the feed network produce less effect on scattering of microstrip patch. A novel aperture coupled microstrip antenna is proposed, which utilizes the chip-resistor load, ground slot and miniaturization, to realize RCS reduction. Aperture coupled antenna with rectangular patch is chosen as the reference antenna. Two antennas are simulated and measured. The measured results show that the designed antenna realizes only 0.5 dB gain loss while RCS are reduced in almost all the frequency band.
A thin internal planar antenna for GSM/DCS with a hollow shorting cylinder suitable for integration with an embedded digital camera for a mobile phone is presented. A small vertical ground plane electrically connected to the system ground plane of the mobile phone is used. The vertical ground plane can function as an effective shield wall between the antenna and the nearby electronic elements in the mobile phone. The method of moments is used to simulate the antenna structure and calculate the radiation characteristics of the antenna.
This paper reports the miniaturization of a microstrip 90 degree coupler by substituting the quarter wave transmission lines employed in conventional 90 degree coupler with its equal circuits consisting of two oblique stubs and an inductor and capacitors. Reduction of the coupler to 27% its size is reported here. This coupler is designed at 1070MHz for using in even harmonic mixers of 3G mobile receivers. Furthermore, the coupler can accurately divide the input signal by two parts with the same power and 90 degree phase difference. Also, the reflection coefficient and the isolation are as good as conventional one and coupling procedure is better than it.
This paper presents a very small size microstrip antenna suitable for WLAN application. The main patch antenna consists of an M-shaped slot with shorting wall. With a shorted triangular parasitic patch and a folded patch overall antenna size is reduced. The simulated and measured results show that by selecting a proper shorting wall width, the proposed antenna can provide an impedance bandwidth of 21.17% covering the 4.93-6.09 GHz band. The antenna size is of order 0.1094λo × 0.1094λo × 0.0544λo (6 × 6 × 3mm3). The proposed antenna has 75% surface size reduction compared to a conventional patch antenna operating at the same centre frequency. The E- and H-plane radiation pattern across the entire operating bandwidth is provided.
In this paper, full-wave analysis of a microstrip-ring resonator capacitively coupled to Microstrip transmission line is presented. The method of the analysis is based on spectral domain in rectangular coordinate system. Since this coordinate system is not compatible with ring structure, triangular basis functions have been utilized for the current distributions on the ring surface. Applying Galerkin's method in spectral domain, the resonant frequencies of the structure and current distributions on the conductors are calculated and the effects of various parameters are studied. To verify the method of analysis, our results are compared with others and the accuracy of the method has been confirmed.
In this paper we have reported soliton solution of one dimensional modified complex Ginzburg Landau equation. The parametric region where such soliton solution is possible is also identified.
This paper reports the miniaturization of a microstrip Wilkinson power divider by substituting the quarter wave transmission lines employed in conventional Wilkinson power dividers with its equal circuit consisting of two stubs and an inductor. Reduction of the device length to 53% its size are reported here. This Wilkinson power divider is designed at 2140MHz for using in 3G-UMTS receivers. Furthermore, the second harmonic suppression is realized in this configuration and its frequency response is similar to low pass filters because of inductor. Also, the dividing procedure, the reflection coefficient and the isolation are as good as conventional Wilkinson.
A new deembedding method in permittivity measurement of ferroelectric thin film material is proposed in this paper. By measuring the two scattering matrixes of the two samples with different length, the propagation constant of the actual network under test (ANUT) can be obtained. Further more, the permittivity would be extracted. The results show that though the proposed deembedding method, the error induced by embedding can be eliminated successfully and the propagation constant of the ANUT can be extracted accurately.
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