Analysis And Design Of Microwave Devices Based On Ridge Gap Waveguide Technology
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Analysis and Design of Microwave Devices Based on Ridge Gap Waveguide Technology
The usage of high frequency microwave devices is rapidly increasing with the advances achieved in the communication systems. However, the standard guiding structures have high losses such as microstrip technology, or difficulty in manufacturing such as in the case of waveguides. The newly developed ridge gap waveguide (RGW) technology resolves the problems above as it has low losses and does not require electrical contacts as required in the waveguides. The concept of RGW is simple as it allows the wave propagations in the guiding part and eliminates the leakage in all other directions. The region that surrounds the ridge consists of two parallel surfaces; one is a perfect electric conductor (PEC) and the second is a perfect magnetic conductor (PMC). The gap between the two surfaces should be less than a quarter wavelength. Periodic conducting nails realize the PMC that practically has a possible bandwidth 2.5:1 and in some cases exceeds 3:1. Usually, the design of these surfaces relies on the unit cell analysis that is based on determining its band gap, the estimation of the band gap is performed numerically. The band gap of the cell is the operating bandwidth of the complete structure. For the first time, we presented a method to measure the band gap from s-parameter measurements. Utilization of the broadband characteristics strongly depends on the proper design of the transition between the RGW and the standard guiding structures and connectors. Most of the available transitions make use of around one-third of the possible bandwidth. Therefore, we present new transitions that utilize the whole possible bandwidth of the RGW. The presented work can be divided into four major parts. Several microwave components are designed based on the RGW such as power divider, hybrid couplers, and a circulator. New methods are presented for efficient and accurate design of these components. One of the main contributions is related to the RGW circulator design; it's an accurate design procedure that can be used with other technologies as well. In addition, a new setup to measure the low relative permittivity of thin materials such as fabrics is presented. An example of a leaky wave antenna using split slot arrays is presented. These studies highlight the RGW advantages and can be considered as a step towards the standardization of this technology.
Design and Analysis of Microwave Devices Based on Gap Waveguide Technology
Among state-of-the-art guiding structures, the Ridge Gap Waveguide (RGW) is a promising technology, as it minimizes the losses in high-frequency applications and supports wide operating bandwidth. There is another form of the guiding structures that utilize the idea of the Artificial Magnetic Conductor (AMC) surfaces such as Groove Gap Waveguide (GGWG). It has the same advantages as the RGW in terms of losses, and immunity to leakages without the need for electrical contacts, but with different dispersion characteristics. The RGW supports a quasi-TEM mode while the GGWG supports TE modes as it's a different form of the rectangular waveguide. Therefore, GGWG has high power capability comparable to the standard waveguides. As currently, interest is increasing of millimeter wave and microwave applications, the RGW and GGWG are excellent candidates for these applications due to their low loss. It is quite essential to develop microwave components with superior electrical characteristics for such applications. The anisotropic materials have useful physical properties that can benefit the microwave devices, due to their enormous advantages such as high stability and wide bandwidth in the millimeter wave band. Ferrite is an example of such anisotropic materials. Their properties can be deployed to improve the performance of the millimeter microwave devices in terms of higher stability, wider band, and high power handling. Taking advantages of the above characteristics, the research work in this thesis is focusing on their use for microwave and millimeter wave frequencies. The presented devices are responsible for the feeding of the antenna systems. Moreover, they can be deployed in different applications such as antenna beamforming. In this thesis, the differential phase shifters and the orthomode transducers (OMTs) are realized by different technologies that are suitable for both of the microwave and the millimeter wave bands that serve different applications of the wireless communication systems. The research work done can also be summarized in two parts. The first part starts with the study and investigation of the ferrite material properties and their role in the microwave devices. Then, later providing a new accurate model with mathematical formulas for the differential ferrite phase shifter. Moreover, a new design methodology for those phase shifters is presented. Later, the ferrite is applied in the conventional waveguide, Substrate Integrated Waveguide (SIW), and RGW technologies. In the second part, study, design, and analysis of different types of the orthomode transducers are presented. They are devices responsible for combining and separation of two orthogonal polarizations. The presented OMTs has a compact size with excellent performance. Several OMT types are considered such as the one-fold symmetry, asymmetric, and two-fold symmetry. The first mentioned two OMTs are realized by deploying the waveguide technology, while the two-fold symmetry OMT is based on the GGWG technology. It has the ability to design a feeding network for an array of antennas based on the GGWG technology. Moreover, this OMT is fabricated using 3D printed technology that uses the carbonated plastic material, in which two copper layers are covering all the structure surfaces by electroplating. This fabrication is a new promising technology that is not expensive, lightweight and less complex than traditional machining. However, there are some concerns about power handling and high temperature withstanding. Such problems might have a solution in the future with a more accurate 3D metallic printers.
Surface Electromagnetics
Author: Fan Yang
language: en
Publisher: Cambridge University Press
Release Date: 2019-06-20
Provides systematic coverage of the theory, physics, functional designs, and engineering applications of advanced electromagnetic surfaces.