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Circuit World
Number of Followers: 17  
  Hybrid Journal Hybrid journal (It can contain Open Access articles)
ISSN (Print) 0305-6120
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  • Design and optimization of a low voltage RF switch MEMS capacitance using
           genetic algorithm and Taguchi method
    • Pages: 53 - 64
      Abstract: Circuit World, Volume 45, Issue 2, Page 53-64, May 2019.
      Purpose This paper aims to design, optimize and simulate the Radio Frequency (RF) micro electromechanical system (MEMS) Switch which is stimulated by electrostatically voltage. Design/methodology/approach The geometric structure of the switch was extracted based on the design of Taguchi-based experiment using the mathematical programming and obtaining objective function by the genetic meta-heuristic algorithm. Findings The RF parameters of the switch were calculated for the design of Taguchi-based S11 = −5.649 dB and S21 = −46.428 dB at the working frequency of 40 GHz. The pull-in voltage of the switch was 2.8 V and the axial residual stress of the proposed design was obtained 28 MPa and the design of Taguchi-based S11 = −4.422 dB and S21 = −48.705dB at the working frequency of 40 GHz. The pull-in voltage of the switch was 2.5 V and the axial residual stress of the proposed design was obtained 25 MPa. Originality/value A novel complex strategy in the design and optimization of capacitive RF switch MEMS modeling is proposed.
      Citation: Circuit World
      PubDate: 2019-06-19T01:13:11Z
      DOI: 10.1108/CW-02-2019-0014
  • Stability investigations based on two-port describing functions
    • Pages: 65 - 79
      Abstract: Circuit World, Volume 45, Issue 2, Page 65-79, May 2019.
      Purpose Stability of a nonlinear, tuned amplifier has been investigated based on the describing function method. On stability, this paper means global asymptotic stability. The tuned amplifier comprises a saturated amplifying device with feedback and two resonators, at the input and the output. Describing function method here means introduction of the two-port describing functions. Design/methodology/approach Describing function method is applied, extended for two ports. Results from complex analysis and matrix algebra are heavily used. The two resonators have identical resonant frequency and bandwidth. Instability is represented by non-vanishing output perturbation for zero-input perturbation. Applying a simple transistor model with saturation and feedback, stability is analyzed in the form of output voltage as a function of input voltage. Findings Two-port scattering and admittance describing functions have been introduced. At a certain input voltage amplitude, instability appears in the form of unwanted sidebands, then at a higher input voltage, instability disappears, in good agreement with experiments. The hand calculated stability limits are in good agreement with the computer analysis. Originality/value The paper is based on an early publication of the author (Baranyi and Ladvánszky, 1984). Here, the full material is presented, explained step by step, extended and revised. All neglections that were earlier made in the author’s paper have been avoided here. This paper has significant tutorial value as well.
      Citation: Circuit World
      PubDate: 2019-06-05T11:07:01Z
      DOI: 10.1108/CW-12-2018-0105
  • Design of the variable frequency oscillator in DC-DC converter
    • Pages: 80 - 85
      Abstract: Circuit World, Volume 45, Issue 2, Page 80-85, May 2019.
      Purpose Because of the logic delay in the converter, the minimum turn on time of the switch is influenced by the constant time. When the inductor current gets to the threshold of the chip, the control signal will delay for a period. This makes the inductor current rising with the increasing of the clock and leads to the load current out of control. Thus, this paper aims to design an oscillator with a variable frequency protection function. Design/methodology/approach This paper presents an oscillator with the reducing frequency applied in the DC-DC converter. When the converter works normally, the operating frequency of the oscillator is 1.5 MHz. So the inductor current has enough time to decay and prevent the power transistor damaging. After the abnormal condition, the converter returns to the normal operating mode automatically. Findings Based on 0.5 µm CMOS process, simulated by the HSPICE, the simulation results shows that the frequency of the oscillator linearly decreases from 1.5 MHz to 380 KHz when the feedback voltage less than 0.2 V. The maximum deviation of the oscillator frequency is only 6 per cent from −50°C to 125°C within the power supply voltage of 2.7-5.5 V. Originality/value When the light load occurs at the output stage, the oscillator frequency will decrease as the load voltage drops. The test results shows that when the circuit works in the normal condition, the oscillator frequency is 1.5 MHz. When the load decreased, the operating frequency is dropped dramatically.
      Citation: Circuit World
      PubDate: 2019-01-24T09:27:54Z
      DOI: 10.1108/CW-01-2018-0003
  • The resin-flowing model in prepreg lamination of print circuit board
    • Pages: 86 - 92
      Abstract: Circuit World, Volume 45, Issue 2, Page 86-92, May 2019.
      Purpose This paper aims to show a resin-flowing model based on Darcy’s law to display the flowing properties of prepreg during lamination. The conformity between the model and experimental results demonstrates that it can provide a guideline on print circuit board (PCB) lamination. Design/methodology/approach Based on the theoretical derivations of Darcy’s law, this paper made an analysis on the flow of prepreg in the pressing process, according to which a theoretical model, namely, resin-flowing model was further formulated. Findings This paper establishes a resin-flowing model, according to which two experiment-verified conclusions can be drawn: first, the resin-flowing properties of material A and B can be improved when the heating rate is between 1.5 and 2.5 min/°C; second, increased pressure gradient can add the amount of flowing resin, mainly featured by increasing pressure and reducing filled thickness of prepreg. Originality/value This model provides guidance on setting lamination parameters for most kinds of prepregs and decreasing starvation risk for PCB production.
      Citation: Circuit World
      PubDate: 2019-01-16T12:00:55Z
      DOI: 10.1108/CW-04-2018-0023
  • Stabilization and circuit implementation of a novel chemical oscillating
           chaotic system
    • Pages: 93 - 106
      Abstract: Circuit World, Volume 45, Issue 2, Page 93-106, May 2019.
      Purpose This paper is aimed at investigating a novel chemical oscillating chaotic system with different attractors at fixed parameters. The typical dynamical behavior of the new chemical oscillating system is discussed, and it is found that the state selection is dependent on initial values. Then, the stabilization problem of the chemical oscillating attractors is investigated analytically and numerically. Subsequently, the novel electronic circuit of the proposed chemical oscillating chaotic system are constructed, and the influences of the changes of circuit parameters on chemical oscillating chaotic attractors are investigated. Design/methodology/approach The different attractors of the novel chemical oscillating chaotic system are investigated by changing the initial values under fixed parameters. Moreover, the active control and adaptive control methods are presented to make the chemical oscillating chaotic systems asymptotically stable at the origin based on the Lyapunov stability theory. The influences on chemical oscillating chaotic attractors are also verified by changing the circuit parameters. Findings It is found that the active control method is easier to be realized by using physical components because of its less control signal and lower cost. It is also confirmed that the adaptive control method enjoys strong anti-interference ability because of its large number of selected controllers. What can be seen from the simulation results is that the chaotic circuits are extremely dependent on circuit parameters selection. Comparisons between MATLAB simulations and Multisim simulation results show that they are consistent with each other and demonstrate that changing attractors of the chemical oscillating chaotic system exist. It is conformed that circuit parameters selection can be effective to control and realize chaotic circuits. Originality/value The different attractors of the novel chemical oscillating chaotic system are investigated by changing the initial values under fixed parameters. The characteristic of the chemical oscillating attractor is that the basin of attraction of the three-dimensional attractor is located in the first quadrant of the eight quadrants of the three-dimensional space, and the ranges of the three variables are positive. This is because the concentrations of the three chemical substances are all positive.
      Citation: Circuit World
      PubDate: 2019-06-17T02:10:53Z
      DOI: 10.1108/CW-12-2018-0108
  • Techniques of impedance matching for minimal PCB channel loss at 40 GBPS
           signal transmission
    • Abstract: Circuit World, Ahead of Print.
      Purpose This paper aims to analyze the negative impact of surface mount (SMT) pad and imperfect via structure such as stub, pad, non-functional pad (NFP) and anti-pad on the signal integrity at 40 Gbps transmission on printed circuit board (PCB) due to impedance mismatch or discontinuity. The optimized modeling of via and SMT structures is performed to achieve minimal impedance mismatch and insertion loss less than 10 dB for six-inch full path transmission line between transmitter and receiver on PCB at Nyquist frequency 20 GHz. Design/methodology/approach This work is split into two phases. The first phase involves optimization of via and SMT structures in three-dimensional electromagnetic (3DEM) simulation using Hyperlynx Via Wizard and Keysight EMPro software, respectively, followed by analysis of time domain reflectometry (TDR) and insertion loss (Sdd21). Whereas, in the second phase, full path hybrid mode simulation involving vias for signal layer transition, a 6-inch PCB channel and SMT pads is performed using Keysight ADS software to observe the TDR, Sdd21 and eye diagram at 40 Gbps transmission. Findings Imperfect via and SMT structures have a negative effect on signal reflection and attenuation. The optimized via and SMT minimizes the impedance mismatch by 81 per cent and insertion loss by 4.5 dB, ultimately enlarging the eye diagram opening to achieve minimal data loss at receiver with 40 Gbps transmission. Originality/value The results of original empirical research work on signal integrity analysis that optimizes the PCB channel design to achieve 40 Gbps signal transmission are presented in this study. It serves as a reference guide for high-speed PCB layout design.
      Citation: Circuit World
      PubDate: 2019-06-21T09:14:37Z
      DOI: 10.1108/CW-01-2019-0004
School of Mathematical and Computer Sciences
Heriot-Watt University
Edinburgh, EH14 4AS, UK
Tel: +00 44 (0)131 4513762
Fax: +00 44 (0)131 4513327
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