Wyniki 1-2 spośród 2 dla zapytania: authorDesc:"Muhammad Tajammal CHUGHTAI"

Temperature Compensated Bias Supply Circuit for Photodiodes DOI:10.15199/48.2018.10.48

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Introduction Temperature compensation becomes necessary in situations where the ambient temperatures keep varying or the components itself are prone to temperature changes as their operation goes along[1]. The situation effects the overall operation of electronic circuitry in terms that required output keep changing drastically. In this regard several approaches have been adopted by researchers, these pertain to use of Zener diodes, Peltier elements and NJFETs [2] as reference for compensation. Nishida etal also presented a temperature compensation model to work with avalanche photodiodes [3], whereas,Webb et al [4] claimed a quantum efficiency of up to 100% after carrying out temperature compensation for an RAPD. Tajammal and Nagi [5] presented a temperature compensation solution for laser diodes. Suggested Methods for Temperature Compensation There are a number of techniques which help to compensate temperature variations under various conditions. Three more commonly used techniques are as follows:- a. Operation under constant current. b. Operation of desired components at a constant temperature. c. Biasing of circuitry or components using temperature compensated power supply. Figure 1 [6] shows a scheme for constant current operation for temperature compensation. In this scheme a current stabilized power supply is connected in series to a photodiode so that the device operates under constant current operation as the changes in temperature causes the reverse current to vary. Another method of temperature compensation is possible in which the bias voltage tracks any changes in the temperature and hence adjusts itself by sensing generated reference voltage. Figure 2 [7] shows another scheme of temperature compensation by using another alike component to provide reference voltage for the purpose. However, in order to achieve best and efficient results, it is necessary that both the components i.e. original and referenc[...]

Design of Compact Ultra-Wideband Monopole Semi-Circular Patch Antenna for 5G wireless communication networks DOI:10.15199/48.2019.04.42

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The massive mobile data requirement has increased, in last ten years, mainly due to the video content. This is due to the capability of mobile handsets supporting 4k resolution which requires the data rate of 15.4Mbps[1]. This increase is due to the increasing number of user and viewing time. This will result in an annual traffic of 296.8 excabytes(EB) by 2019[2]. Therefore, 5G communication network (IMT 2020) is the suggested solution to match this high data demand, with a capability of reaching up to data rate of 20Gbps. 5G is not only targeting enhanced mobile broadband (eMBB), but also it has diverse usage scenarios including, ultra reliable and low latency communication (URLLC) and massive machine type communication(mMTC). In order to meet with the design challenges of 5G , frontend antenna layout for base stations and mobile hand set is an intense area of research. Recently, technology of ultra-wideband has received high importance and growth in wireless communication systems due to its remarkable features. Federal Communication Commission (FCC) has allocated a frequency band ranging from 3.1 GHz to 10.6 GHz for such applications [3-8]. These systems are characterized by extreme high data rates over their wide bandwidth, low power consumptions [9-12]. Hence, designing a compact antenna with high performance in terms of operating frequency, radiation pattern, power gain, and fabrication cost remains a challenging task[13-17]. Micro strip patch antennas are widely used in ultrawideband systems due to their advantages such as low cost, simplicity, light weight, and structure size. Thus, proposed antenna is a patch semi-circular antenna fed by a micro strip line as shown in figure 1(a). Next section will present details of the antenna structure and parameters. Antenna Design Fig.1 shows the geometry structure of the proposed semi-circular monopole antenna. The entire design and parametric optimization process have been[...]

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