The paper presents the performances of microstrip patch antennas excited by the aperture-coupling feed that is composed of a T-shaped microstrip feed line and an annular-ring slot. Because the annular-ring slot is designed at a full-wavelength resonant mode, a broad impedance bandwidth can be obtained by combing the resonant modes of the coupling slot and radiating patch; moreover, a low cross polarization is also observed, especially around the direction with maximum gain. For reducing the considerable back radiation induced by the resonant coupling aperture, additional slots are introduced and embedded along the perimeter of the annular-ring slot. Experimental results show that the reformed coupling slot can improve the front-to-back ratio of the aperture-coupled microstrip antenna by more than 5 dB. Simulation analyses are also performed to support the measured results.
This work is dedicated to the study and measurement of the electric and magnetic fields intensities in the vicinity of an antenna array that is used for broadcasting at medium frequencies. The far field distance of a radiating system is usually computed with 2D2/λ which is obtained from the geometry of the problem. Another method to obtain the far field distance using the wave impedance of the electromagnetic wave through the ratio of electric and magnetic field, has been measured and calculated theoretically. The classical and new method to compute the far field distance are compared in this paper in order to show the improves in the calculation. The antenna array used in this work is a monopole plus a parasitic element at medium frequency, which generate a ground wave. Near the antenna, the electric field has vertical and radial components, and the areas are called the reactive near field and the radiated near field. The attenuation of the electric and magnetic fields due to the soil can be neglected for the near field study. The prediction of the levels of field intensity is useful to analyze electromagnetic interference and electromagnetic compatibility. It is also important to verify the regulations of International Standard IEEE C95-1 and the Argentina Regulation 3690 of National Communications Commission (CNC).
In this letter, an easy concept to eliminate the simultaneous switching noise (SSN) in multilayer board is proposed. Use of the low impedance element provides a short path to lead noise to ground, called virtual shield. This method could effectively suppress the first mode of the parallel resonance, and the wider-band suppression could be obtained by array short via. It is also proved that the virtual shield concept has to be placed as the excited source at the same layer.
The design and realization of a ten-element shaped-beam antenna array are presented. A flat-top pattern in the main beam which allows a well-proportioned power distribution in desired zone is achieved by optimizing the amplitudes and phases of array elements using genetic algorithm. Being different from the most optimization in reported literatures, the proposed synthesis has taken the actual element patterns but identical and isotropic ones into account, which can reduce the error between computation and realization. Besides, both the optimized amplitudes and phases are set to be realizable. The array operating at 1.71-1.74 GHz is manufactured and measured. The measured radiation patterns of the proposed array show a flat-top main beam of about 40o and a peak side-lobe level of -20 dB, exhibiting a good agreement with the simulated results.
This paper presents a novel compact power divider with third harmonic suppression and also can provide a direct current(dc) path which could simplify the other active circuits in the complicated phased array antenna system. The proposed power divider achieves 20% size reduction compared to the conventional Wilkinson power divider. From the measured results, it can be seen that the simulated results can instruct the practical circuit very well.
The analytical expression of scattering field from a conductor elliptic cylinder is presented, as the electromagnetic wave propagating vertical to the axis of an elliptic cylinder with arbitrary incident angle and polarization. The obtained result is in agreement with that in the reference when we use this analytical expression to calculate the scattering field from a cylinder. Simulations show that the vertical size of the elliptic cylinder effects greatly the scattering field when we observing it in the direction perpendicular to the direction of the incident wave. The scattering field is strong as the polarization direction of incident wave parallel to the axis of the elliptic cylinder. The algorithm used in the article is valid to investigate the scattering characteristic of other elliptic cylinders. The obtained result offers a theoretical foundation for the practical applications such as electromagnetic remote sensing of target's size and shape.
In this paper a numerical analysis of a periodic planar structure using a uniaxial substrate is shown. The paper means to explore the possibility to use non-conventional substrate to reduce the size of planar radiating structure. The encouraging numerical results set the ground for a further experimental analysis. The presented results can be applied easily to the design of planar antennas, arrays and Frequency Selective Surfaces (FSS). Currently the demand for multiband performance devices that can stay in the palm of the hand has become more compelling. In this light, the advance in planar radiating structure design using non-conventional material with the objective of size reduction is carried out. A FSS resonating at 20.75 GHz has been analyzed. Pyrolytic boron nitrite (PBN), which has an anisotropic dielectric with a relative electric permittivity represented by a diagonal tensor, is adopted as the substrate of the designed FSS to achieve the size reduction while maintaining the FSS performance. The design is then compared with the one that uses isotropic substrate (i.e., RO4003). Comparison shows that the introduction of such a non-conventional medium allows the patch size to be reduced approximately by 20% while maintaining almost the same electromagnetic performance. Issues about size reduction and frequency shifting are further presented and discussed in the paper.
A novel planar omnidirectional array based on Quasi-Yagi antenna was proposed in this paper. The modeling of this antenna and design method based on equivalent circuits has been developed. An eight-unit planar array has been designed, fabricated and measured. Measured results exhibit good performance of the return loss and radiation pattern in horizontal plane. The gain of the array in horizontal plane was about 0 dBi. The un-roundness of the radiation pattern in horizontal plane was about 5 dB.
In this article, method of lines combined with pseudospectral discretization has extended to the analysis of the characteristics of open cylindrical substrate microstrip lines. Numerical results show that the combination benefits from the two methods and has higher efficiency and it is a powerful alternative analytic tool.
Usually, an effective permittivity can be used to describe the molecular polarization of the mixture in the reaction and consequently be used to calculate the transmission and absorption of microwave in the reactant mixtures. In this paper, we propose a method to calculate the effective permittivity of chemical reaction in solution by means of the experimental results. To verify this method, the acetone iodations reaction is employed. The calculated results of complex effective permittivity of the mixtures are in good agreement with the measured results.
This paper presents two compact ring slot antennas which are suitable for the PCS-1900 and the 2.4/5-GHz triple-band operations. The first antenna consists of three annular ring slots. The outer ring is responsible for exciting the first resonant mode where the middle ring excites the second resonant mode. The inner most rings, through their Y-shape-like slots, create a wide upper operating band by combining the third and fourth resonant modes. To improve this antenna, we have employed circular Photonic Bandgap (PBG) structures in order to obtain a smaller slot antenna with better radiation characteristics. In this design, the cross-polarization level in the E-plane has reduced compared to the first antenna by 5.5 dB, 0.3 dB and 4 dB in three resonant bands. Also, the cross-polarization in H-plane has reduced by an amount of 3 dB. In addition, the obtained results show that the co-polarization patterns are very similar in all three frequency bands. In both cases we have reduced the size of antennas to 56% and 42% respectively, of conventional microstrip slot antennas. The simulation results are verified by measurements.
A micro electromechanical phase shifter base on the fractal geometries is proposed to work at Ku frequency band with at least 23% lower actuation voltage compared to the simple rectangular membrane counterparts. In this design the membrane of the switch is chosen to be a Koch fractal and then a distributed MEMS phase shifter is set up by cascading a distinct number of these switches. This phase shifter is analyzed to obtain its parameters such as differential phase shift, group delay, and insertion and return loss. It will be shown that this phase shifter could be used as a low loss multi bit phase shifter system because of its low insertion loss and power consumption.
An increasing attention has been concentrated on nondiffracting Bessel beams, due to their novel properties and prospective applications. In order to study their properties entirely, including the transverse modes, the polarization states and the flow of energy, vector analyses should be done. In this paper, based on auxiliary functions of Hertzian vector potential, nondiffracting Bessel beams are analyzed. The useful results are obtained and presented in this paper.
This paper presents the application of using the macromodels for modeling the interconnections in some fairly complex digital high speed circuits. The analysis which is based on a time domain full wave approach, deals with signal integrity. The results of this simulation are compared with measurements, and sources of error are discussed.
An ultra-wideband exponential tapered slot antenna with new geometrical gratings, which is fed by a nonuniform CPW-slotline balun that is essentially important for the ultra-wide band characteristic, has been introduced in this paper. The measurement shows that the frequency band is from 1.7 GHz to over 13 GHz, among which the VSWR is below -10 dB except 1.7 GHz around (below -9 dB). The gratings are emphasized to make the antenna to perform better radiation characteristics of a comparatively stable, symmetrical pattern and low side lobes through the operating band as well as obviously higher gain and sharper beam width in the low frequency section in comparison with the one without gratings (more than 3 dB at 1.7 GHz).
The phase noise is a very important index to wireless system, especially in millimeter-wave continuous wave radar systems. The phase noise of the signal, which is firstly leaked from transmitter and then mixed to intermediate frequency band by the local oscillator (Tx-IF), will worsen the sensitivity of supper heterodyne radar system used for Doppler velocity detection. In this paper, the coherent analysis is applied on the phase noise after nonlinear process, which shows that the phase noise of the Tx-IF is affected by those factors: the magnitude of the phase noise of the transmitter and that of the local oscillator, and the correlationship between each other. In practice, by reducing the phase noise of the transmitter and that of the local oscillator and ameliorating the correlationship of the two phase noises, the phase noise of the Tx-IF can be improved greatly. Such proposition is successfully applied in the design of a millimeter-wave Doppler radar working at 95 GHz. The experimental measurement shows that the sensitivity of this radar is better than -70 dBm.
The paper describes a novel low profile circularly polarized antenna. The antenna is a single dipole over a particular wire formed panel with high impedance properties. Although the principles of operation for the antenna are general, in this work they are specifically applied to the design and optimization of a FM broadcasting antenna. The distinguishing feature of the design is that it incorporates the following interesting concepts simultaneously: artificial high impedance surfaces or artificial magnetic conductors, materials showing refractive indexes of less than unity (n < 1), and polarizing structures. Another advantageous aspect of the design is the computational efficiency emerging from this fact that the structure is entirely wire made. This way the relevant numerical analysis and optimization can be efficiently carried out by NEC, a one-dimensional (1D) MoM-based EM analyzer.
This paper presents an efficient meshless approach for solving electrostatic problems. This novel approach is based on combination of radial basis functions-based meshless unsymmetric collocation method with projection domain decomposition method. Under this new method, we just need to solve a Steklov-Poincare interface equation and the original problem is solved by computing a series of independent sub-problems. An electrostatic problem is used as an example to illustrate the application of the proposed approach. Numerical results that demonstrate the accuracy and efficiency of the method are stated.
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