Filtronic (United Kingdom)

An open-loop folded microstrip ring resonator is practically demonstrated to exhibit a photonic band-gap (PBG) phenomenon. This is due to the fact that impedance discontinuity at the gap introduces multiple reflections with phase correlation that generates a PBG response. The physical dimensions of this device are significantly smaller than other conventional microstrip PBG structures. Such a device can be easily integrated with other microwave devices without severely affecting space requirements

This chapter contains sections titled: Introduction Experimental Procedure Results and Discussion Conclusions

Geordneter Aufbau: Die Cobalt- und Niob-Ionen in Ba8CoNb6O24 sind vollständig in Abfolgen aus jeweils sieben Schichten mit hexagonaler und kubischer Packung angeordnet. Solche Feststoffe könnten als dielektrische Mikrowellenresonatoren, z. B. im Mobilfunk, interessant sein. In der gezeigten Struktur sind {CoO6}- und {NbO6}-Einheiten als rote bzw. blaue Oktaeder und Ba-Kationen als schwarze Kugeln dargestellt. Supporting information for this article is available on the WWW under http://www.wiley-vch.de/contents/jc_2001/2005/z500135_s.pdf or from the author. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.

Abstract This article provides a broad introduction to III–V semiconductors as a background to device and circuit technologies that use these materials. The reader is introduced to theoretical and practical concepts for this range of alloy semiconductors. The physical and chemical properties and behavior of these materials are discussed. Methods of growing epitaxial layers and fabricating microwave and RF devices are presented. A brief summary of the microwave applications of III–V semiconductors is included together with an overview of the state‐of‐the‐art performance.

One means of tuning planar stripline resonators with top and bottom electric walls and a magnetic sidewall is to include suitable radial and circumferential slots in the resonator plate. The use of a triplet of radial magnetic walls is a standard result in the literature and it has been shown to leave the so-called symmetric pole on the boundary of a planar resonator unperturbed. It is separately understood that a triplet of circumferential magnetic walls in the resonator plate will essentially modify both the dominant symmetric pole and virtual zero only. Both conditions are investigated experimentally. The first-mentioned geometry may enter into the design of three-port circulators using triple impedance poles and the latter in the adjustment of high-quality conventional circulators.

A single ended amplifier with a simple reactive matching is shown to provide stable operation with substantially improved amplifier power-added efficiency (PAE) (>30%) across an ultra-broadband frequency range (2-18 GHz). The amplifier employs a Double Pseudomorphic High Electron Mobility Transistor (DPHEMT) power device.

Rectangular waveguide resonators having different widths can be mixed in order to improve the stopband performance of band-pass filters. Two effective procedures for the choice of the resonator widths are presented and implemented to realise X-band 6-cavity filters which hold 30 dB of attenuation over a frequency range 40% wider than a standard filter. Theoretical and experimental results are shown and commented on.