Comparison of Electromagnetic Band Gap and Split-Ring Resonator Microstrip Lines as Stop Band Structures

In this paper, microstrip lines magnetically coupled to splitring resonators (SRRs) are conquved to electromagnetic bundgup (EBG) nr,rrostrip lines in terns q/ their stop-heard penjbrnmrnce and dimensions. In bath types o/ trunsmis•siou lines, signal propagation is inhibited in it certain jequency bwuL For EBG microstrip lines, the central frequency of such a forbidden band is determined by the period of the structure, whereas in SRR-hased microstrip lines the position of the frequency gap depends on the quasi-static resonant frequency of the rings. The main relevant conrributiun of this paper is to provide a tuning procedure to control the gap width in SRR microstrip lines, and to show that by using SRRs, device dimensions ale much smaller than those required by EBGs in order to obtain similar stop-banal performance. This has been demonstrated by fill-wave electromagnetic simulations and experimentally verified from the characterization ql two fabricated microstrip lines: one with rectangular SRRs etched on the upper substrate side, and the other with a periodic perturbation cf'strip width. For similar rejection and 1-(;H,. gap width centered at 4.5 Gllz, it has been found that the SRR microstrip line is•,fve times shorter. In addition, no ripple is appreciable in the allowed band for the .SRR-hared structure, whereas due to dispersion, certain mismatch is expected in the EBG prototype. Due to the high-frequency selectivity, controllable gap width, and small dimensions, it is believed that SRR coupled to planar transmission lines can have an actual impact on the design of stop-band filters compatible with planar technology, and can be an alternative to present solutions based on distributed approaches or EBG

High Selectivity Filter Employing Stepped Impedance Resonators, Series Capacitors and Defected Ground Structures for Ultra Wide Band Applications

The paper presents a compact planar Ultra Wide Band ¯lter employing folded stepped impedance resonators with series capacitors and dumb bell shaped defected ground structures. An interdigital quarter wavelength coupled line is used for achieving the band pass characteristics. The transmission zeros are produced by stepped impedance resonators. The ¯lter has steep roll o® rate and good attenuation in its lower and upper stop bands, contributed by the series capacitor and defected ground structures respectively.

Optimal Design of a Surface Mounted Permanent-Magnet BLDC Motor for Spacecraft Applications

This paper presents the optimal design of a surface mounted permanent-magnet (PM) Brushless direct-current (BLDC) motor meant for spacecraft applications. The spacecraft applications requires the choice of a motor with high torque density, minimum cogging torque, better positional stability and high torque to inertia ratio. Performance of two types of machine configurations viz Slotted PMBLDC and Slotless PMBLDC with Halbach array are compared with the help of analytical and finite element (FE) methods. It is found that unlike a Slotted PMBLDC motor, the Slotless type with Halbach array develops zero cogging torque without reduction in the developed torque. Moreover, the machine being coreless provides high torque to inertia ratio and zero magnetic stiction