When a microstrip patch antenna is brought closer than 0.2λ to an identical patch the resonant frequency of that antenna changes from the designed frequency. In this paper numerical results for the resonant frequency are presented from a theoretical analysis of the mutually coupled H-plane microstrip patch antennas with confirming experimental results. We have also established the relation between resonant frequency of E-plane coupled and H-plane coupled microstrip patch antennas.
Based on the theory about charge moment tensor and the magnetic moment of a rotational charged body, and by means of Eulor's equation for a rotational rigid body in classic mechanics, the Lagrangian and the dynamic equation of a charged dielectric rigid body under a uniform magnetic field has been derived; Also two symmetric simple cases have been solved or analyzed under condition of slow rotation and no gravitation, the corresponding invariants have also been found.
In the recent years, extensive studies have been done to design space-time codes appropriate for communications over fading channels in multiple input-multiple output (MIMO)systems. Most of these designs have been based upon the assumption that the channel fading coefficients are uncorrelated hence independent jointly Gaussian random variables. Naturally the best strategy in such situations that the elements of the channel matrix are independent is to employ diversity techniques to combat the adverse effects of these fading media and thus the most famous space-time codes, i.e., orthogonal and trellis codes have been designed with an eye to realizing the maximum attainable diversity order in a MIMO system. In this paper, we will remove this almost ever-present yet practically difficult to meet condition and shall introduce a new linear space-time block code that due to having some inherent redundancy as well as diversity is wellsuited to correlated fading channels. We will discuss the properties of the proposed code, derive its maximum likelihood (ML) decoder and provide simulation results which show its superiority to the highly used orthogonal space-time block codes in a wide range of signal to noise ratios in correlated fading channels.
Fractional curl operator has been utilized to study the fractional order surface waveguides. Fractional order surface waveguides may be regarded as intermediate step of two surface waveguides which are related through the principle of duality. Fractional eigenvalue equations are examined at the interface between dielectric medium and free space, for various values of fractional order parameter result in different fractional surface wave modes.
Closed-form expressions for the input impedance of halfwavelength rectangular microstrip antennas fed by coaxial connectors of different sizes at any point on any one of the non-radiating edges and open-circuited at the other ends are derived. Good agreement between computed and measured data is obtained.
Antenna diversity is a well-known technique to enhance the performance of wireless communication systems. In order to create an antenna diversity system on a wireless device, two or more antenna elements could be placed in positions. However, it is difficult to implement multiple antennas on handheld terminal. A compact planar inverted-L diversity antenna for handheld terminals is provided. Three diversity antennas operating at 2.15 GHz are designed. The isolation is found to be better than 13 dB and the usable bandwidth is about 13% in measurement. The measured radiation patterns are obtained that the proposed diversity antenna attains 2 dBi gain.
This paper presents a novel wideband bandpass filter making use of complementary split-ring resonator (CSRR) as the basic resonant unit. The resonant characteristic of CSRR is carefully studied through full wave analysis. The coupling of CSRR structure is very strong that can be used to realize wideband filter with small insertion loss. A filter with center frequency at 3.5 GHz, passband from 3.1 GHz to 3.8 GHz is designed and fabricated. The measured results are in good consistent with simulated results.
In this paper, using moment method in the spectral domain, full wave analysis of two orthogonal microstrip transmission lines in two layered PCB board is presented. First, using 1-dimensional spectral domain method, the propagation constants and the currents on each line are obtained, without considering of the other line. Then, using Galerkine's method in 2 dimensional spectral domain, the scattering parameters of the structure are calculated. The results of our analysis are compared by the quasi-TEM approach. Comparisons show good agreement between our results and quasi-TEM approach.
The generation of the picture out of the SAR raw data is a computational intensive task. Both range compression and azimuth compression utilized Fast Fourier Transform (FFT) algorithms and Inverse Fast Fourier Transform (IFFT) in order to perform convolution with respective reference signal. Thus FFT and IFFT occupied about 70% of the total computation operation in SAR image formation. In this paper a modified algorithm based on conventional FFT is proposed to optimize the computation performance. It is shown that the proposed algorithm can essentially achieve better performance with minimum computational burden compare to conventional FFT.
This paper proposes an improved adaptive approach involving Bacterial Foraging Algorithm (BFA) to optimize both the amplitude and phase of the weights of a linear array of antennas for maximum array factor at any desired direction and nulls in specific directions. The Bacteria Foraging Algorithm is made adaptive using principle of adaptive delta modulation. To show the improvement in making the algorithm adaptive, results for both adaptive and nonadaptive algorithms are given. It is found that Adaptive Bacteria Foraging Algorithm (ABFA) is capable of improving the speed of convergence as well as the precision in the desired result.
A new mathematical method and proposal for generation of shape invariant potentials using supersymmetric quantum mechanics is introduced. For this purpose the potential term in the Schrodinger equation is expressed in terms of the super potential. The obtained equation transformed into well known ordinary second order differential equation. Using standard technique, the Nikiforov-Uvarov (NU) method the superpotential in the Schrodinger equation is expressed in terms of the parameters appeared in the NU-approach concluding to a nonlinear differential equation. By solving the obtained equation and using relation between superpotential and potential the shape invariant potentials are obtained. The proposed method is general and straightforward for introducing of the shape invariant potentials.
This paper presents a new enhancement technique for infrared images. This technique combines the benefits of homomorphic image processing and the additive wavelet transform. The idea behind this technique is based on decomposing the image into subbands in an additive fashion using the additive wavelet transform. This transform gives the image as an addition of subbands of the same resolution. The homomorphic processing is performed on each subband, separately. It is known that the homomorphic processing on images is performed in the log domain which transforms the image into illumination and reflectance components. Enhancement of the reflectance reinforces details in the image. So, applying this process in each subband enhances the details of the image in each subband. Finally, an inverse additive wavelet transform is performed on the homomorphic enhanced subbands to get an infrared image with better visual details.
An exponentially tapered structure is introduced into multimode interference (MMI) devices. Compared with a parabolically tapered structure,which has been successfully used in MMI devices, this structure can further reduce the length of these devices. The performances of the 1 × 2 MMI coupler with exponentially tapered structure,such as the optical transmission,the wavelength response and the fabrication tolerance,are investigated by the 2D finite difference beam propagation method. Results show that the exponentially tapered MMI coupler exhibits a similar property to that with a parabolically tapered structure.
New electromagnetically coupling fed low profile broadband high gain E-shaped microstrip antennas (MSA) were proposed for high speed wireless networks in IEEE 802.11 a and j standards. The proposed antenna uses an E-shaped microstrip patch covered by a radome and fed by an electromagnetically coupled strip. To validate this concept, a single antenna element and a sub-array were designed, built and measured. The measured results indicate that the element and the sub-array cover the band from 4.8 to 6.0 GHz (return loss < −10 dB) and produce a gain of 8 dBi and 11 dBi, respectively. The developed prototypes may find their applications in wireless communication networks as mobile or base antennas.
A closed form analytic solution is introduced for arbitrary Coupled Nonuniform Transmission Lines (CNTLs). First, the differential equations of CNTLs are written as a suitable matrix differential equation. Then, the matrix differential equation is solved to obtain the chain parameter matrix of CNTLs. Afterward, the voltage and current of lines are obtained at any point using the chain parameter matrix. The validation of the introduced solution is studied, finally.
A new miniature ultra-wideband exponential tapered slot antenna with gratings, which is fed by a 180 degree microstrip phase shifter network, has been introduced in this paper. The switch characteristic and the reflecting loss of the phase shifter is also analyzed. Some subminiature rectangular gratings are etched at the front and back end, as a result of which, the inner band characteristic is improved and the frequency band of the antenna is extended to more than 3 : 1 (S11 < −10 dB). The radiation pattern has good direction property in the entire bandwidth and favorable symmetrical endfire radiation characteristic as well as more than 10 dB gain in the central frequency band.
Uniqueness of the initial-boundary value problems for a Tellegen media is studied. Initial-boundary value problems for a Tellegen Medium are summarized for the sake completeness; the conservation of energy for such a medium is reviewed. Sufficient conditions are given for the positive definiteness of the energy stored in a Tellegen media due to the fields. It is shown that the if the energy stored in a Tellegen medium is positive definite, then an initialboundary value problem for a Tellegen media has only one solution, if it exists.
Antenna array design techniques are focused on two main classes: uniformly spaced antenna arrays and the non-uniform spacing case. These include techniques based on mathematical programming, such as constrained programming and non-linear programming. More recently, meta-heuristics approaches have been successful at designing antenna arrays . In this work, this paper presents efficient methods of genetic algorithm (GA), memetic algorithm (MA) and tabu search algorithm (TSA) for the synthesis of linear antenna design. We present three examples of antenna array design to compare the efficiency of the algorithms through simple design to complex design. The GA, TSA and MA has been used to optimize the spacings between the elements of the linear array to produce a radiation pattern with minimum SLL and null placement control.
Two compact CPW-fed band-pass filters using dual-mode resonator are proposed and studied - one resonator with two unequal corner-cut elements located at two diagonal corners of a conventional micro-strip patch and the other with unequal crossed slots at the center of a conventional micro-strip patch. In this paper, adjusting the length of corner-cut element and the crossed slot are mainly studied. By use of HFSS, the simulation results are given and analyzed. The simulation results show that the pass-band of the filter(a) may be adjusted over the bandwidth range from 4.9% to 16%, and the pass-band of the filter(b) may be adjusted over the bandwidth range from 5.4% to 8.2%, and filter(b) with cross-slot has smaller size than filter(a) with corner-cut to meet the same application demand. According to the simulation results, to design a filter which works at 1.65 GHz, the configuration of filter(b) is adopted owning to smaller size. finally, filter(b) with len1=20.2mm and len2=20.4mm is fabricated and measured, which has a minimum insertion loss of 2.48 dB in its pass-band.
In this paper, design and analysis of a novel broadband V-shaped monopole antenna is presented. The proposed antenna has a simple configuration to fabricate with low cost. The antenna is composed of two elliptical conducting plates connected to the two edges of a small horizontal rectangular plate and placed over a small circular ground plane. The designed antenna has a very wide bandwidth range of 3-18 GHz, low cross polarization, relatively high gain and good far-field radiation characteristics in the entire operating bandwidth. To obtain the broad bandwidth, the antenna dimensions have been optimized. A comprehensive parametric study has been carried out to understand the effects of various parameters and to optimize the performance of the final design. The designed antenna is simulated with software packages CST microwave studio and Ansoft' HFSS in the operating frequency range. Simulation results for VSWR and far-field radiation patterns of the antenna over the frequency band 3-18 GHz are presented and discussed.
A novel uni-planar electromagnetic Band Gap (EBG) structure incorporated with inter-digital capacitor and meandered line inductor (ML-ID-EBG) is presented, this novel structure significantly enlarges the fringe capacitance to reduce sized cells, as well as increases the equivalent inductance to widen the relative bandwidth. Its design is detailed in this paper, and several experimental results are presented, the improved properties of the proposed ML-ID-EBG are examined, as compared with a conventional UC-EBG and a novel EBG incorporated only with inter-digital capacitor (ID-EBG).
The adiabatic parameter dynamics of non-Kerr law optical solitons is obtained in this paper by the aid of soliton perturbation theory. The various kinds of perturbation terms that arise exhaustively in the context of optical solitons are considered in this paper. The new conserved quantity is also used to obtain the adiabatic dynamics of the soliton phase in all cases of non-Kerr laws studied in this paper. The non-Kerr law nonlinearities that are considered in this paper are power law, parabolic law as well as the dual-power law.