In this paper, an ultra wideband antenna employing a defected ground structure is presented. The radiating element is a circular patch on which a fractal based geometry is inscribed in the form of slots and excited by a tapered feed-line for impedance matching. The antenna has an impedance bandwidth of 8.2 GHz (117% at centre frequency of 7GHz) and a peak gain around 6 dB. To improve the impeda...

Relying on abrupt phase discontinuities, metasurfaces characterized by a transversely inhomogeneous surface impedance profile have been recently explored as an ultrathin platform to generate arbitrary wave fronts over subwavelength thicknesses. Here, we outline fundamental limitations of passive gradient metasurfaces in molding the impinging wave and show that local phase compensation is essent...

A discrete-time analog echo canceller is described that reduces the echo in the front end of Gigabit Ethernet twisted-pair interfaces. Echo cancellation in the analog domain by means of four taps reduces the complexity of the digital echo canceller and crosstalk cancellers. Designed in a 0.4m CMOS technology, the circuit employs an LMS algorithm to adapt to the cable length and impedance discon...

Time Domain Reflectometry (TDR) is commonly used as a convenient method to determine the characteristic impedance of a transmission line, or to quantify reflections caused by discontinuities along or at the termination of a transmission line. TDR can also be used to measure quantities such as the input capacitance of a voltage probe, the inductance of a jumper wire, the end to end capacitance o...

The method of moments (MOM) in conjunction with the generalized scattering matrix (GSM) approach is proposed to analyze transverse multilayered structures in a metal waveguide. The formulation incorporates ports as an integral part of the GSM formulation and so the resulting model can be integrated with circuit analysis. The proposed technique permits the modeling of interactive discontinuities...

[1] We consider the use of lumped voltage and current sources in engineering lightning return stroke models with emphasis on those including a tall strike object. If the model is to be used for computing remote electric and magnetic fields, we suggest a representation of the lightning channel as a transmission line energized by a lumped voltage source, with the voltage magnitude being expressed...

My research focuses primarily on optimal control of systems in domains with contacts, equipped with variable impedance actuators. The control of such robots is non-trivial due to the the discontinuity in the dynamics which is introduced by mechanical contact with the environment. The traditional optimal control approach is designed to handle smooth continuous system dynamics for tasks over a pr...

The grid-connected dual-PWM adjustable speed drives (ASDs) modulate the energy of motor torque oscillation and inject it into power system, potentially causing low-frequency (LFO) in grid. In this study, considering harmonic common-modulation both-side converters, precise sequence impedance models are derived for ASDs using linearisation method. Based on ASD, oscillation, which is equivalent to...