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Purpose Helical coil electromagnetic launchers (HEMLs) using motion-induced commutation strategy solve the problem of synchronization control perfectly. HEMLs can meet the requirements of multiple applications such as the electromagnetic catapult, electromagnetic mortar and high-velocity coilgun. The trade-off between the velocity and efficiency is an important basis for these different applications. To optimize such objectives before actual design, the purpose of this paper is to focus on the efficient and flexible calculation model and algorithm. A novel structure of HEML is proposed after the transient simulation by this algorithm, which can improve the energy conversion efficiency and suppress the muzzle arc without affecting the velocity too much.Design/methodology/approach The equivalent circuit model of the launcher is established and the governing equations are derived. A combination of the four-stage Runge–Kutta method and the trapezoidal quadrature formula are used to solve the governing equations.Findings With smaller number of turns in the coils of HEML, the velocity is larger and the efficiency is lower. The non-uniform HEML is an effective option to improve the energy conversion efficiency and to suppress the muzzle arc with almost the same muzzle velocity as the conventional HEML.Originality/value The paper presents a common model and a flexible fast numerical method which can be used in multi-objective optimization of HEMLs such as the genetic algorithm. A new structure of the non-uniform HEML is proposed to improve the energy conversion efficiency and to suppress the muzzle arc of the launcher. [ABSTRACT FROM AUTHOR]

Purpose - The purpose of this paper is to design and measure an H-plane substrate integrated waveguide (SIW) 72?GHz backfired horn antenna chip. The SIW horn was fabricated on a standard 0.5-µm GaAs process with substrate thickness of 100?µm. Design/methodology/approach - Planar SIW horn design method with standard GaAs circuit design rule was adopted. The input reflection coefficient and output antenna gain was simulated at the FEM-based 3D full-wave EM solver, Ansoft HFSS and measured at the Agilent E8361C Network Analyzer and Cascade 110?GHz probe station. Findings - The measured input -6 dB bandwidth is about 0.9?GHz at a center frequency of 72.39?GHz. The maximum antenna power gain extracted from the path loss at 72.39?GHz is about -3.64?dBi. Research limitations/implications - Thin substrate exhibits larger capacitance and energy stores rather than radiates. Flat cutting restricts the arc lens design and results in the radiation plane mismatches to the air. Simple taper transition design makes the input bandwidth much narrower. The problems can be further improved by selecting thicker substrate and the multi-section input CPW GSG pads to microstrip transition. Practical implications - Unlike the traditional anechoic chamber, the antenna measurement station is exposed to the open space and chip antenna was supported by the FR4 substrate and the metal probing station plate. A fully characterization of the antenna open space environment before the measurement is needed. Originality/value - An H-plane SIW 72?GHz horn antenna was designed and studied. The antenna was using the GaAs 0.5-µm MMICs process design rule includes the SIW designed cylindrical metal bars all being restricted in standard rectangular shape. Compare to traditional bulky waveguide horn antenna, the antenna chip size is only 1.8×1.7?mm2. The on-wafer measurement is conducted to measure the input return loss and the maximum antenna power gain of the on-chip antenna. The designed on-chip SIW horn antenna is useful for the integrated design of the E band GaAs MMICs single-chip RF transceiver. [ABSTRACT FROM AUTHOR]