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A dual‐gate aluminium gallium arsenide (GaAs)/GaAs pseudomorphic high electron mobility transistor is analysed based on the distributed modelling approach, wherein the transistor is considered as an active multi‐conductor transmission line. Discretisation of the governing matrix Telegrapher's equation is carried out using the implicit Crank–Nicolson‐finite‐difference time‐domain (CN‐FDTD) method. The results obtained from the proposed method are compared with the results of the conventional leap‐frog (LF) FDTD scheme. It is observed that the unconditionally stable CN method is in good agreement with the LF method even by increasing the time step size by the factor of 5000, leading to a dramatic decrease in the central processing unit time. [ABSTRACT FROM AUTHOR]

An explicit finite difference time domain method is proposed for modelling of composite right-/left-handed active multiconductor transmission lines in time domain. For the first time, the concept of active composite right-/left-handed transmission lines is considered in field effect transistor (FET) modelling. In this work, based on the distributed model, the FET is considered as an active multiconductor transmission line in the mm/wave frequency range. In this modelling technique, the FET is divided into 2 different parts, the active part, represents the intrinsic equivalent circuit of the transistor, while the passive part symbolizes the device electrodes. The finite-difference time-domain scheme is proposed for the analysis, and the results of this technique are compared with the ones obtained from simulations. Furthermore, the stability issue is investigated and the sufficient condition for stability is derived. [ABSTRACT FROM AUTHOR]

This paper has proposed a new pre-processing stage algorithm to enhance the overall performance of current simplification algorithms in analog circuits. This pre-process stage takes place after the calculation of symbolic transfer function and before the main core of the simplification algorithm. The detailed stages of this pre-process are completely independent of the main simplification and symbolic transfer function algorithm. As such, the pre-process algorithm can be easily added to any simplification algorithm to improve the total simplification performance. The use of this command, which is based on the stack decision method, helps the pre-process algorithm to obtain a high-process speed. Based on the CPU time simulation results for a transfer function with 139 terms, it is expected to have a total CPU time in the simplification of a 9820 term of about 28 to 30 seconds pulse and 1.2 to 4.9 seconds for the pre-process algorithm. Finally, a total method, which involves the combination of this pre-process algorithm with the main simplification algorithm is proposed in, and a CPU time of about 30 to 35 seconds is needed for simplifying a huge transfer function with 9820 terms. The addition of extra pre-process algorithm to the main simplification algorithm will reduce the total CPU time of simulation from 820 to 35 seconds, indicating a reduction of 95% in the total needed simulation time. [ABSTRACT FROM AUTHOR]

ABSTRACT In this paper, we have investigated plasma column excited by surface-waves using monopole plasma antenna. Since the plasma frequency has an important role in conductivity of the plasma column and antenna radiation characteristics, determining the distribution electron density and plasma frequency in the inhomogeneous plasma column axis is particularly important. For this purpose, the plasma column is modelled by fluid equations for high-frequency discharges. Because of significant advantages such as high power handling capability at 2.45 GHz, the surfaguide launcher is chosen from the other conventional launchers to propagate the surface wave along plasma column. The surfaguide is experimentally excited an argon gas-filled tube at a pressure of 0.2 torr as a surface-wave plasma source. In this work, because of safety considerations about high power radiation, plasma frequency measurements was impractical using conventional methods. Therefore, a new system is designed consists of a solid-state VCO, amplifier, circulator, attenuator and two double-ridged horn antennas. The plasma frequency is obtained close to 5.7 GHz, which is consistent with theoretical concepts. © 2017 The Authors. Microwave and Optical Technology Letters. Microwave Opt Technol Lett 59:806-811, 2017 [ABSTRACT FROM AUTHOR]

ABSTRACT This article presents a novel reflective phase shifter based on wideband multi-section 3-dB hybrid coupler in slot-coupled structure. By terminating coupled and transmission ports of coupler with rectangular microstrip loads, reflective phase shifter is achieved. It designed on multilayer Rogers RO4003C substrate. The configuration consists of elliptically shaped transmission line and the combination of rectangular and elliptical shaped slots on the ground plane. To improve characteristics of the designed coupler especially in lower frequency band, multi-section transmission line and altering shape of the slot on ground is proposed. By etching extra rectangular slots on the ground plane the overall size reduction is achieved. Measurement results of the proposed coupler demonstrate coupling of 3 ± 0.7 dB with 90° ± 0.6 phase shift over 1-6 GHz (143%). The novel reflective phase shifter based on the designed coupler provides phase deviation less than 0.7° on 1.2-4.8 GHz (120%). The obtained return loss is better than 10 dB as well as insertion loss is less than 1.2 dB at the frequency band of interest. © 2017 Wiley Periodicals, Inc. Microwave Opt Technol Lett 59:567-573, 2017 [ABSTRACT FROM AUTHOR]

In the millimeter-wave frequency range, electromagnetic effects can significantly influence a device behavior. As the core of modern communication systems, active devices such as field-effect transistors require up-to-date models to accurately integrate such effects, especially in terms of noise performance because most of communication systems operate in noisy environments. Based on the active coupled line concept, a novel approach for efficient noise performance modeling of millimeter-wave field-effect transistors is proposed. This distributed model considers the effect of wave propagation along the device electrodes, which can significantly affect the noise performance, especially in the millimeter-wave range. Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]