Filtering Technique for Stabilization of Marching-on-in-Time Method

In this paper, digital filters are used for the stabilization of the marching-on-in-time (MOT) method. A methodology of designing a proper filter using optimization techniques is proposed here. Since the proposed procedure considers the important part of the spectrum of the excitation signal, the designed filter does not degrade the accuracy of the MOT method. Further, the procedure for the efficient stabilization of the MOT method by a set of filters is proposed and verified on the examples

Multi-Objective Synthesis of Filtering Dipole Array Based on Tuning-Space Mapping

In the paper, we apply tuning-space mapping to multi-objective synthesis of a filtering antenna. The antenna is going to be implemented as a planar dipole array with serial feeding. Thanks to the multi-objective approach, we can deal with conflicting requirements on gain, impedance matching, side-lobe level, and main-lobe direction. MOSOMA algorithm is applied to compute Pareto front of optimal solutions by changing lengths of dipoles and parameters of transmission lines connecting them into a serial array. Exploitation of tuning space mapping significantly reduces CPU-time demands of the multi-objective synthesis: a coarse optimization evaluates objectives using a wire model of the filtering array (4NEC2, method of moments), and a fine optimization exploits a realistic planar model of the array (CST Microwave Studio, finite integration technique). The synthesized filtering antenna was manufactured, and its parameters were measured to be compared with objectives. The number of dipoles in the array is shown to influence the match of measured parameters and objectives

Acceleration of Marching on in Time Method for TD-EFIE by Equivalent Dipole Moment Method and its Analysis

The paper is focused on the application of the equivalent dipole moment (EDM) method to accelerate the marching on in time (MOT) method for the time domain electric field integral equation (TD-EFIE). The implicit MOT scheme with the EDM method for the TD-EFIE is derived and analyzed. It is shown that the derived scheme is faster than the conventional one, even if it is not used for modeling electrically large structures. Since the conventional implicit MOT scheme for the TD-EFIE is sensitive to small changes of its coefficients, the full-value using of the MOT scheme with the EDM approximation requires an appropriate technique (e.g. a preconditioning) to obtain a well-conditioned scheme

Laguerre Polynomials’ Scheme of Transient Analysis: Scale Factor and Number of Temporal Basis Functions

The paper is focused on two important parameters of the scheme with weighted Laguerre polynomials: the scale factor of time axis and the number of temporal basis functions. In the first part of the paper, the approach for the determination of the number of temporal basis functions is proposed. Its number is determined during the run of the scheme. In the second part of the paper, the influence of the choice of the scale factor on the efficiency of the scheme, with the possibility of its optimum choice, is investigated. The investigations show that a chosen scale factor strongly influences the efficiency of the scheme. If the scale factor is not chosen close to the optimum one, the scheme becomes time-consuming. However, a simple formula for its prediction can not be given. The choice of the scale factor seems to be the weak point of the scheme with Laguerre polynomials

Modeling Microwave Structures in Time Domain Using Laguerre Polynomials

The paper is focused on time domain modeling of microwave structures by the method of moments. Two alternative schemes with weighted Laguerre polynomials are presented. Thanks to their properties, these schemes are free of late time oscillations. Further, the paper is aimed to effective and accurate evaluation of Green\'s functions integrals within these schemes. For this evaluation, a first- and second-order polynomial approximation is developed. The last part of the paper deals with modeling microstrip structures in the time domain. Conditions of impedance matching are derived, and the proposed approach is verified by modeling a microstrip filter

Low-profile Circularly Polarized Antenna Exploiting Fabry-Perot Resonator Principle

We designed a patch antenna surrounded by a mushroom-like electromagnetic band-gap (EBG) structure and completed it by a partially reflective surface (PRS). EBG suppresses surface waves and creates the bottom wall of the Fabry-Perot (FP) resonator. PRS plays the role of a planar lens and forms the top wall of the FP resonator. The novel PRS consists of a two-layer grid exhibiting inductive and capacitive (LC) behavior which allows us to obtain a reflection phase between –108 and +180 degrees. Thanks to this PRS, we can control the height of the cavity in the range from λ/2 to λ/300. Obtained results show that the FP resonator antenna enables us to achieve a low profile and a high-gain. The patch is excited by a microstrip transmission line via the cross-slot aperture generating the circular polarization. Functionality of the described concept of the FP antenna was verified at 10 GHz. The antenna gain was 15 dBi, the impedance bandwidth 2.3% for |S11| < –10 dB, and the axial ratio bandwidth 0.6% for AR < 3.0 dB. Hence, the antenna is suitable for narrowband applications. Computer simulations show that the microwave FP antenna can be simply redesigned to serve as a source of circularly polarized terahertz waves

Multicriteria Optimization of Antennas in Time-Domain

An original approach to the time-domain multicriteria optimization of antennas is presented. For a given excitation pulse, the time-domain objective function takes the “time-domain impedance matching”, distortion of responses at the feeding point and in a desired radiating direction (with respect to the excitation pulse), and the radiated energy in the desired direction into account. The objective function is tested on the optimization of a bow-tie antenna using the particle swarm optimization. The proposed approach is suitable for the design of broadband antennas

Circularly Polarized Rectangular Ring-Slot Antenna with Chamfered Corners for Off-Body Communication at 5.8 GHz ISM Band

This paper deals with a substrate integrated waveguide (SIW) circularly polarized rectangular ring-slot antenna with chamfered corners designed for 5.8 GHz ISM frequency band for off-body communication. The antenna consists of a substrate integrated waveguide, which operates in the fundamental mode TE10, and the rectangular ring-slot radiator with chamfered corners etched in the top wall of the SIW. It radiates a right-handed circularly polarized (RHCP) wave in the boresight direction. Experimental results prove that the proposed antenna located in free space achieves the impedance bandwidth of 2.41 % (for the reflection coefficient less than -10 dB) and the RHCP gain of 6.57 dBi, and the impedance bandwidth of 2.6 % and the RHCP gain of 6.98 dBi for its location on the phantom. The axial ratio (AR) bandwidth (for the AR less than 3 dB) is 0.9 % for both configurations

Design of a Linearly Polarized HMSIW U-Slot Antenna

In this paper, a characteristic modal analysis and a design guide of a linearly polarized HMSIW U-slot antenna is proposed. The presented characteristic modal analysis of the antenna explains its multi-modal behavior in the centimeter frequency band. Further, in this paper there is a design guide of the antenna for several dielectric substrates. Exploitation of the design guide is demonstrated on the design of several antenna examples which are finally experimentally verified in a laboratory environment

X-Band Circularly Polarized HMSIW U-Slot Antenna

In this paper, a circularly polarized U-slot half-mode substrate integrated waveguide (HMSIW) antenna is proposed. It is based on a combination of U-shaped slot etched in the HMSIW top wall and a shorting via placed between the area bounded by the slot and the HMSIW bottom wall. The antenna is designed for the operating frequency of 10 GHz, parametrically studied, fabricated and experimentally verified. Experimental results proves that the fabricated prototype radiates a left handed circularly polarized (LHCP) electromagnetic wave and it achieves the impedance bandwidth of 11.9 % for the reflection coefficient less than -10 dB, the axial ratio (AR) bandwidth 2.2 % for AR less than 3 dB, and the LHCP peak gain of 6 dBi. The proposed antenna combines attractive features like low profile, low weight and low cost fabrication process