ElectroMagnetic Design Made Easy
A permanent magnet linear generator (PMLG) is simply a generator made up of a stator, translator, and air gap. The stator is usually made up of copper windings and laminations which aim at minimizing the eddy current losses. The translator consists of permanent magnets that can be either rings, cylinders, or rectangles and made of rare earth material. Depending on the required force and the air gap magnetic field, the magnets can be arranged radially, axially, or in Halbach fashion.
Lowpass filters are essential ingredients of microwave and wireless devices and systems. However, they suffer from a limited harmonic rejection in the stopband. A remedy which is traditionally used by microwave engineers is to add attenuation poles to extend the stopband bandwidth. Unfortunately, such workaround usually increases the overall size of the filter which is, definitely, undesirable and hinders the ever-increasing demand for miniaturization. In recent years, a new technique to limit the harmonic rejection in the stopband, has become popular among microwave engineers. This technique, which consists of etching-out slots or defects on the ground plane of a printed microstrip board, is called a Defected Ground Structure (DGS). You can actually think of a DGS as a simplified form of Electromagnetic Band Gap (EBG) structure.
Wireless Power Transfer (WPT) is a technique to transmit electric power without connecting wires using electromagnetic fields and waves. Generally speaking, WPT methods can be categorized to either non-radiative –near field- or radiative –far field. A power transfer is considered non-radiative if the maximum diameter of both the receiver and transmitter is less than half of the operating wavelength (𝐷𝑚𝑎𝑥 < 𝜆/2) and the transfer distance 𝑟 is less than the wavelength (𝑟 < 𝜆). Similarly, if 𝐷𝑚𝑎𝑥 > 𝜆/2 and 𝑟 < 2𝐷𝑚𝑎𝑥2 / 𝜆, it is still considered a non-radiative situation. However, a transfer is considered radiative if 𝐷𝑚𝑎𝑥 < 𝜆/2 and 𝑟 > 2𝜆 or if 𝐷𝑚𝑎𝑥 > 𝜆/2 and 𝑟 > 2𝐷𝑚𝑎𝑥2 / 𝜆. In terms of frequencies, the aforementioned conditions, translate to a frequency range of 10kHz-200MHz, and 300MHz-300GHz for non-radiative and radiative, respectively.
The miniaturization of antenna arrays imposes on the designer to place a large number of elements in a small footprint. This action gives rise to the so-called mutual coupling, which, in turn, causes crosstalk and distortion leading to the deterioration in the antenna performance and potential distortion of the radiation pattern. We won’t exaggerate if we say that such mutual coupling is the biggest obstacle to the miniaturization of antenna arrays. Over the years, antenna designers have found workarounds but with limited success. The workarounds include bandgap and ground defected structures as well as 3-dimensionncal vias.