China
Africa
Explore chapters and articles related to this topic
Sensor Applications
Published in Luc B. Jeunhomme, Single-Mode Fiber Optics, 2019
As is any optical interferometer, the FOG sensitivity is limited by photon noise. Detection of phase shifts as small as 10-6 to 10-7 rad should then be possible with several microwatts of returning light power, but when compared to the total phase accumulated along the coil (about 109 rad for 100 m of silica fiber at a 840 nm wavelength), this means detecting one part in 1015 to 10l6. To get this incredible number happens to be feasible because of the fundamental principle of reciprocity of light propagation in a linear medium. This requires only the use of a truly single-mode waveguide filter (single spatial mode and single polarization state) at the common input–output port of the ring interferometer [34]. This ensures that, at rest, both counterpropagating waves follow exactly the same path in opposite directions. Then they suffer exactly the same propagation delay through the coil and their phase difference is nulled out. This yields a so-called reciprocal configuration (Fig. 8.3) which drastically improves the stability of the interferometer. Good alignments are obviously still needed, but only to optimize a high throughout power in the total system, which is a much less stringent requirement than ensuring a phase stability of 10-7 rad, that is, a mechanical stability of 10-5 nm.
Principle of Filters
Published in Yoshihiro Konishi, Microwave Electronic Circuit Technology, 2018
Dielectric Waveguide Filter [16] By using the high-dielectric material, we not only can decrease the size but also easily create the magnetic wall between the air and the ceramic. Therefore, a λg/2 waveguide resonator with short ends can be replaced by a λg/4 waveguide resonator with open and short ends.
Photonic Network
Published in Naoaki Yamanaka, High-Performance Backbone Network Technology, 2020
T. Miyazaki et al. report in Paper 7.5 the optical bridge and switch function for protection networks. This function is used in the ADM (Add Drop Multiplexer) system. An experimental system is realized by using a AWG (Arrayed Waveguide Filter) and fiber amplifiers. The architecture is applicable to the WDM restoration ADM network.
Compact LTCC bandpass SIW filter with high selectivity for 5G exploiting mixed coupling
Published in Electromagnetics, 2021
Xueyuan Guan, Xiangjun Zhang, Shang Yin, Yushun Liu
With the speedy development of wireless communications and radar technology, there is demand of the component and the subsystem with good performance and small size. The microwave or millimeter-wave filters are the important components of the wireless communication system, and so it is vital to design the compact filter with high performance (Thomas 2003). The conventional rectangular waveguide filter has high superior performance, such as small insertion loss, high power handling capacity, but it has the shortcomings of bulkiness, high fabrication cost, and non-easy integration with planar circuit. Recently, a new planar structure called substrate integrated waveguides (SIWs) is proposed to design microwave filter or antenna. SIWs offer an attractive substitution through printed planar structures combining the low-loss performance of conventional rectangular waveguides with easy integration of printed planar transmission lines. The SIW not only has the merits of rectangular waveguide structure, such as high quality factor, high-power handling capacity, but also has low cost mass production, easy fabrication (Lee, Yoo, and Yook 2009; Potelon et al. 2008; Sun et al. 2020). During the past decades, much attention has been paid to the design of all kinds of SIW filters. Many types of SIW filter topologies have been developed to realize miniaturization of filters including half-mode SIW (HMSIW), quarter-mode SIW (QMSIW), and eighth-mode SIW (EMSIW), which have small size. However, many of those filters are fabricated exploiting conventional PCB process, which only have one or two layers of the dielectric; the volume of the filter cannot be reduced to the large extent (Jones and Daneshmand 2019). Moreover, these structures have radiation loss and are difficult to realize. As we know, in wireless communication system, in order to diminish the influence of interference signal, the selectivity of filter need to be increased. The conventional method is to increase the number of resonators or introduce input–output coupling. A large number of resonators will increase the volume of the filter. A better way is to introduce the mixed couplings to generate transmission zeros (TZs) at desired frequencies to increase the selectivity of the bandpass filter.