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Perspectives on the History of Computing
Published in José López Soriano, Maximizing Benefits from IT Project Management, 2016
The Z4 machine represents a milestone in the history of computers; it was the first computer in the world to be sold as a product. Until that time, computing machines were designed and built by the inventor for a specific purpose, and usually with the financing of a customer or institution. The Z4 was able to reproduce punch cards by using instructions contained within the machine itself. This made it possible to reproduce programs and programming, and it also facilitated making program modifications or the correction of programming mistakes, in contrast to earlier machines, which did not have this capability. The Z4 included about 22,000 relays, had a memory of 500 words of 32 bits, and weighed 1000 kg. It could perform calculations at a rate of about 1000 instructions per hour, and managed a comprehensive instructions set that could solve complicated scientific operations.
New highly narrowband miniature microstrip bandpass and bandstop filters based on SIR components for wireless systems
Published in Electromagnetics, 2021
SIRs are characterized into symmetrical and asymmetrical varieties, as described in Figure 2. In general, in SIR structures, a thinner width of the microstrip section possesses a bigger impedance as compared with a wider one. Explicitly, Z1< Z2 is for symmetrical SIR, and Z4> Z5 is for asymmetrical SIR, as illustrated in Figure 2. Correspondingly, d1 and d2 stand for electrical lengths for symmetrical SIR, whereas e1 and e2 signify electrical lengths for asymmetrical one. Characteristically, symmetrical SIR includes three step-impedance segments involving two similar impedance and electrical length at each end. An impedance ratio of SIR has principally specified the dimensions condition for symmetrical SIR.
Design of microstrip bandpass filters based on stair-step patch resonator
Published in International Journal of Electronics, 2019
Yaqeen Sabah Mezaal, Ayman S. Al-Zayed
Stepped Impedance Resonator (SIR) technique is Transverse Electromagnetic (TEM) or semi TEM mode transmission line resonator that has dual or more lines with dissimilar characteristic impedances. This approach has the benefit of simple assembly and takes a smaller amount of size than comparable low-pass filter using stubs. As a consequence of the radiations, transverse resonances and other disadvantageous properties, SIR technique is inappropriate for microwave frequencies greater than 20 GHz. Nevertheless, for frequencies more than 20 GHz, this weakness point turns out to be a negligible issue with the latest electromagnetic simulators and contemporary technologies available to microwave engineers (Mezaal & Ali, 2016). SIRs can be classified into symmetrical and asymmetrical types. As a rule in SIR technique, the narrower width of microstrip segment has greater impedance than wider microstrip segment. Accordingly, Z1<Z2 for symmetrical SIR and Z4>Z5 for asymmetrical SIR as depicted by Figure 1. Accordingly, D1 and D2 are electrical lengths for symmetrical SIR while n ad m are electrical lengths for asymmetrical one. Mostly, symmetrical SIR has three step-impedance segments including dual identical impedance and electrical length at both ends. The condition of dimensions of a symmetrical SIR is fundamentally specified by the impedance ratio of SIR (K). In general, if the impedance ratio is higher than 1, the harmonics responses will sway nearby the centre frequency. On the other hand, if the impedance ratio is smaller than 1 as shown in Figure 1(a), the harmonics responses will be moved away from the centre frequency, therefore that this specific feature is favourite to be realistic for a filter design. Alternatively, the asymmetrical SIR as shown in Figure 1(b), can be used to reduce size as well as suppressing undesirable signals. In this paper, the idea of symmetrical and asymmetrical SIRs reported in (Namsang & Akkaraekthalin, 2010), has been adopted to construct a microstrip resonator in form of stair-step topology. It consists of two asymmetrical SIR elements joined to symmetrical SIR base section as depicted in Figure 2.