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Published in Philip A. Laplante, Comprehensive Dictionary of Electrical Engineering, 2018
difference-mode signal (2) ratio of the electrical capacity of a condenser, which has a given material as the dielectric, to the capacity of an identical condenser, but with air as the dielectric. (3) permittivity of a medium normalized to the permittivity of free space; a measure of the response of a dielectric to an applied electric field. (4) an electric property of an insulator or semiconducting material, which describes how differently electric fields will behave inside of the material as compared to air. As an example, er = 12.9 for GaAs as compared to er = 1 for air. In integrated circuits, an effective dielectric constant (eeff ) is used, since the electric fields supported by the signals traveling through the conductors on the circuit flow through both air and the insulator or semiconductor simultaneously. dielectric discontinuity interface between two media with different dielectric permittivity properties. dielectric medium medium that is polarizable but relatively nonconducting. dielectric resonator an unmetallized dielectric object of high dielectric constant and high quality factor that can function as an energy storage device. dielectric resonator antenna (DRA) an antenna where a dielectric resonator is used as the radiation element. dielectric resonator [stabled] oscillator (DRO) a dielectric resonator is a cylindrically shaped piece of material, or "puck," that has the properties of having low-loss resonant frequencies that are determined primarily by the size of the cylinder. Placing a dielectric resonator near a microstrip line can form a resonant circuit that will frequency stabilize a voltage-controlled oscillator. dielectric slug tuner system of two movable dielectric pieces of material placed on a transmission line for the purpose of matching a wide range of load impedances by means of placing the dielectrics in proper positions. dielectric step discontinuity the junction between different dielectric waveguides. dielectric waveguide a waveguide that relies on differences in permittivity among two or more materials to guide electromagnetic energy without the need for ground planes or metallic strips. Such guides of rectangular, circular, elliptical, and other cross sections are made of dielectric materials and used for transmitting signals. Transmission is accomplished by the total internal reflection mechanism inside the waveguide. difference amplifier See differential amplifier.
Improvement of the stopband spurious window for a dual-mode dielectric resonator filter by new coupling technique
Published in International Journal of Electronics, 2018
Saad Luhaib, Nutapong Somjit, Ian C. Hunter
Microwave dielectric resonator (DR) filters are widely employed in modern microwave communication systems due to their high Q-factor, temperature stability and compact size (Liang & Blair, 1998; Zhongxiang, Chang, & Xianliang, 2011). Nowadays, the requirements of these filters are becoming more challenging because of the limitations in frequency spectrum and the high data rate demand. Single-mode resonators have been achieved to operate as DR filters with low loss in wireless systems (Cohn, 1968; Zaki and Chun- ming, 1986). Multi-mode DR filters offer a reduction of size without compromising the electrical performance (Mansour, 2004). In 1982, Fiedziuszko reported the first dual-degenerate mode in a dielectric-loaded cavity filter (Fiedziuszko, 1982), which allowed a size reduction ratio of 8.3% compared with standard . To further reduce the size, Mansour (Memarian & Mansour, 2009) proposed a new DR configuration for size reduction consisting of a half cut cylindrical ceramic puck exhibiting dual mode performance at a certain ratio. A four poles bandpass filter prototype was designed and measured with a spurious free window of 600 MHz and a size reduction compared with dual mode. One of the drawbacks of multi-mode DR filters is their poor spurious window which is less 300 MHz (H¨oft, 2010).
Design, Fabrication and Characteristics of Eco-Friendly Microwave Absorbing Materials: A Review
Published in IETE Technical Review, 2022
Geetika Verma, Kamla Prasan Ray
With the increasing use of microwave frequency for obtaining larger bandwidth in electronic circuits, it has become essential to provide shielding from EM pollution from/to nearby systems. Agricultural-based eco-friendly absorbers can be used inside the enclosures to reduce EMI. Single and multi-layer eco-friendly absorbers can be utilized in applications such as microwave devices, antenna applications, electromagnetic compatibility and various other microwave measurements, as shown in Figure 7. Absorber materials can also be employed in a number of the waveguide and co-axial microwave components [90]. Other applications of such microwave absorbers can be mini anechoic chambers [75] to be operated in laboratories for antenna measurements [91], L-shaped moveable chambers to act as walls. The single and multi-layered absorbers can also be utilized as radar absorbing materials for tents and other mobile vehicles in military applications. The absorbers with low dielectric losses can act as a substrate for designing antennas, replacing FR-4 and other similar substrates. Such materials can also be used as a substrate for dielectric resonator antennas. Ullah et al. [92] designed a microstrip patch antenna on a substrate made from eco–friendly material rice husk. Coco-husk as substrate was utilized to design a multiple-input multiple-output (MIMO) antenna with very high port isolation of >20 dB for triple-band applications [93]. A simple one layer metamaterial microwave absorber utilizing coconut coir fiber of dimensions 10 × 10 × 1 mm was simulated [79]. Also, agricultural residues such as rice husk powders have been utilized as fuel for biomass for micro grid applications [94].