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Guided Wave Propagation and Transmission Lines
Published in Mike Golio, Commercial Wireless Circuits and Components Handbook, 2018
W.R. Deal, V. Radisic, Y. Qian, T. Itoh
A variety of planar transmission lines have been demonstrated, including microstrip, coplanar waveguide (CPW), slotline, and coplanar stripline. The cross-section of each of these planar transmission lines is shown in Figs. 12.6(a–d). Once the dielectric substrate is chosen, characteristics of these transmission lines are controlled by the width of the conductors and/or gaps on the top planes of the geometry. Of these, the microstrip is by far the most commonly used planar transmission line. CPW is also often used, with slotlines and coplanar striplines being the least common at microwave frequencies, for a variety of reasons that will briefly be discussed later. In this section, we will describe the basic properties of planar transmission lines. Because of its prevalence, the microstrip will be described in detail and closed form expressions for the design of the microstrip will be given.
Planar Transmission Lines
Published in S. Raghavan, ®, 2019
First in the planar transmission line family is the stripline, which is homogeneous and has TEM mode as the dominant mode of propagation. The basic structure of the homogeneous strip transmission line consists of a flat strip conductor situated symmetrically between two large ground planes, first proposed by Barret (1951) has pure TEM mode as the dominant mode of propagation. The suspended stripline, the most useful variant of the stripline (inhomogeneous transmission line), has the effective dielectric constant close to that of air. Edge-coupled suspended substrate lines have a lower loss and less sensitivity to physical dimensions than an equivalent microstrip or stripline. Shielded stripline corrects for the effect of side walls at a finite distance.
Determining dielectric properties of nematic liquid crystals at microwave frequencies using inverted microstrip lines
Published in Liquid Crystals, 2022
Haofeng Peng, Yongwei Zhang, Senlai Zhu, Murat Temiz, Ahmed El-Makadema
It is very important to measure the effective dielectric constant accurately for the LC to be used. Table 2 summarises different measurement methods of liquid crystals across the 5–40 GHz range, and it also gives the relative dielectric anisotropy () and measurement error on permittivity for different LC mixtures. In [31–33], the permittivity characteristics of LCs can be determined by using the resonant technique, which offers high sensitivity and accurate results for effective dielectric constants, but the resonant method has a weakness of being appropriate for individual frequency. In [34], a broadband coaxial transmission line method is used to characterise LCs between 360 MHz and 23 GHz. Even though the broadband method can determine the dielectric constants of LCs over a wide range of frequencies, it offers a relatively low accuracy. The method in [35] proposes a planar transmission line for the characterisation of the NLC in the 60 GHz band. One of the advantages of this method is that the structure allows the application of the bias field to the LC through the strips. However, this method achieves lower accuracy than the ones based on resonator. In [36], a microstrip line method is used to obtain the permittivity of the LCs. For this purpose, a unique LC cell is formed, and the measurements are based on the inverted microstrip line through applying the bias voltage to the LC cell using a bias tee. A metamaterial absorber has been used at 90–120 GHz for LC characterisation in [37].
General design of N-way Bagley power dividers with arbitrary unequal output power splitting ratios using a new iterative algorithm
Published in Electromagnetics, 2021
Mohammad R. Rawashdeh, Asem S. Al-Zoubi, Nihad I. Dib, Ahmad A. Almousa
Two examples are presented in this section to confirm the accuracy of the developed N-way BPD design algorithm. These examples are 11-way and 13-way BPDs which, to our knowledge, are presented for the first time in this paper. These BPDs are designed using the presented algorithm in Figure 4 by finding the impedance values for the transmission lines (TLs) between adjacent output ports, where the electrical length for these lines is 90° at the design frequency. A 50 Ω port impedance is used where calculations are taken at the center frequency of 1 GHz. To validate the presented algorithm, the calculated design impedances are used to find the S-parameters. Three steps of validation are presented through this paper: simulation of the designed BPDs using both ADS (ADS, Advanced Design, System, Keysight EEsof EDA 2017) and HFSS (HFSS, High Frequency Structure Simulator Based on the Finite Element Method, version 15.1, ANSYS Corporation 2008) softwares in addition to comparing simulated S-parameters with measured values. In both examples, milling fabrication for both BPDs is used using an on-chip PCB microstrip planar transmission line with Rogers RO4003C substrate with dielectric constant εr = 3.38, thickness = 0.81 mm, and loss tangent, tanδ = 0.0027. An Agilent N5242A PNA-X Network Analyzer is used to measure the S-parameters. Finally, we compare simulated and measured values for transmission coefficients, output port matching and output port isolation parameters for both 11-way BPD with output power ratio 4:5:4:2:3:5:3:2:4:5:4 and 13-way BPD with output power ratio 5:9:3:2:3:2:4:2:3:2:3:9:5.
Compact half-mode SIW bandpass filter with high-frequency selectivity
Published in Electromagnetics, 2018
Zongrui He, Kaijun Song, Zihang Luo, Maoyu Fan, Yu Zhu, Yong Fan
High-performance bandpass filters (BPFs) is an important component in the wireless communication systems (Deng et al., 2011; Liu., Song, and Fan 2012; Mo, Song, and Fan 2014; Mo, Song, and Pan et al. 2013; Song, Hu, and Fan et al. 2013; Song, Pan, and Fan et al. 2012; Song, Pan, and Xue 2012; You, Chen, and Zhu et al. 2013; Young-Ho and Rebeiz 2014). Compared to traditional planar transmission line structure, substrate integrated waveguide (SIW), synthesized on a planar substrate with linear periodic arrays of metallic vias or metallic slots by standard printed circuit board or other planar circuit processes, has provided a useful technology for designing high-factor and low-loss filters (Deng et al., 2011; Young-Ho and Rebeiz 2014).