A Compact Lowpass Filter with Ultra Wide Stopband using Stepped Impedance Resonator

In this paper, a compact asymmetric-shaped microstrip lowpass filter (LPF) using a stepped impedance resonator is presented. An ultra wide stopband with high attenuation in the stopband region, within very small circuit area is achieved for the proposed filter using novel asymmetric structures for resonator and suppressor. The transmission zeros of the resonators can be adjusted as a function of high impedance and low impedance microstrip lines, and due to the asymmetric structure, the proposed suppressing cell can be located within the resonator structure without occupying a large area. For verification, a 2.92 GHz LPF is designed and fabricated. The experimental results, in comparison with the other LPFs, show that the proposed LPF has significant advantages in the stopband characteristics with acceptable sharp roll off. The measured passband insertion loss is below 0.1 dB, and the rejection band over -20 dB is obtained from 3.42 GHz to 36.2 GHz. The size of filter corresponds to compact electrical size of 0.156 λg × 0.128 λg, where λg is the guided wavelength at 2.92 GHz. Also, the maximum variation of the group delay in 80 percent of the passband region is only about 0.2 ns

Self-selection, earnings, and out-migration: A longitudinal study of immigrants to Germany

In this paper we examine the process of out-migration and investigate whether cross-sectional earnings assimilation results suffer from selection bias due to out-migration. Our 14 year longitudinal study reveals that emigrants are negatively selected with respect to occupational prestige and to stable full time employment. Our results show no selectivity with respect to human capital or gender. The likelihood of return migration is strongly determined by the range and nature of social attachments to Germany and origin countries. It is also the highest during the first five years since arrival, and grows higher toward retirement. Selective emigration, however, does not appear to distort cross-sectional estimates of earnings assimilation in a relevant way. Copyright Springer-Verlag 2003J61, J2, C4, Return migration, immigrant assimilation, event history,