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Planar Transmission Lines
Published in S. Raghavan, ®, 2019
The suspended microstrip is a variant of the microstrip with an air gap between the substrate and the ground plane, which is shown in Figure 2.10. The inverted microstrip differs from the suspended microstrip in which the strip conductor is situated on a lower surface of the dielectric substrate facing the ground plane, which is shown in Figure 2.11. Both suspended and inverted microstriplines can also be viewed as special cases of the suspended stripline, with one of the ground planes removed. These structures retain the advantages of the suspended stripline in terms of achieving larger strip dimensions and lower dissipative losses with respect to the microstrip. In comparison with the suspended microstrip, the inverted microstrip has the advantages of reduced radiation loss by virtue of having the strip conductor below the substrate. However, because the air gap involved is too small (typically on the order of 1 mm or less), incorporation of semiconductor devices becomes very difficult in this configuration.
Full-corporate-feed high-gain planar array antenna with cross-loop slots
Published in Electromagnetics, 2021
Yufeng Liu, Jiyu Liang, Liping Han, Wenmei Zhang, Fangyuan Chen
There are totally 8 × 8 cross-loop slots etched on the top layer. The slots couple the electromagnetic wave propagating along the suspended stripline and then radiate it out to form a directional radiation pattern with high-gain.
Development of high power 20 dB directional coupler for Ion Cyclotron Resonance frequency system of Tokamak
Published in International Journal of Electronics Letters, 2022
Earlier studies of directional coupler have been reported by the type of transmission line such as coaxial, suspended stripline, micro strip, and waveguide (Gao et al., 2015), (Keshavarz et al., 2012). The micro-strip (Lin et al., 2011; Lu et al., 1998; Smolarz et al., 2017) usually have low power capacity and high losses, whereas suspended stripline (Lin et al., 2011), (Shekhovtsov et al., 2014; Sledkov et al., 2007) used to decrease the losses and increase the power capability. Various commercial couplers (Microwave communications laboratories, Inc; Pasternack; Pulsar microwave corporation; SigaTek) available in the market also have lower power handling capability. For coaxial type coupler (Jain & Yadav, 2017; McCurdy & Choi, 1999; Mirzaei et al., 2009; Rathi et al., 2008), one has to compromise between bandwidth and power capacity. Whereas waveguide coupler (Kou et al., 2012) are not suitable for application ranging between 10 MHz and 350 MHz due to large size of waveguide. Designing of high power coupler up to 2 kW using suspended stripline is the best suitable for our application. Our objective is to develop a high power directional coupler with compact size, which can handle 2 kW, continuous wave (CW) RF power. This paper presents the development of a 2 kW, 20 ± 0.3 dB directional coupler in the frequency range of 140–200 MHz. To obtain a light coupling (<20 dB) at high power is a challenging task. It also requires a needful arrangement for heat dissipation and for stable coupling response. Since, the coupler is designed for 2 kW power handling capability and lower VHF range 140–200 MHz, its size is expected to be very large (around 530 mm at electrical length of λ/4 at lower frequency). The design of the proposed coupler takes care of the minimum gap required to prevent the breakdown and other requirements. Its size has been reduced up to 50% while maintaining the proper gaps, insulation and other parameters without any deterioration in desired outcome. This paper also analysed the dielectric breakdown strength using electric field distribution inside the coupler, and the average power handling capability is determined using numerical analysis. The designed directional coupler has been fabricated and tested using Vector Network Analyser (VNA). The test results obtained as, return loss better than 30 dB, isolation better than −35 dB and coupling flatness of 20 ± 0.3 in 140–200 MHz frequency range. The developed coupler has also been tested using 36 watt power amplifier, where test results are found in agreement to the VNA test results. The work presented in this paper is helpful for the design and development of high power coupler in radio frequency (RF) range and can be required in various applications such as RF Plasma, radar, navigation, satellite, and research, etc.