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RF/microwave systems require switches to achieve tunability and reconfigurability. MEMS switches have always been a priority due to excellent RF performance (low insertion loss and high isolation). In this work, we present an RF Micro-Electro-Mechanical-System (RF MEMS) series switch that provides insertion loss less than 0.6 dB (on switch) and isolation better than 15 dB (off switch) at 40GHz. The designed switch consists of serpentine arms on the fixed end and two free-moving arms on another end. These free arms have individual contact points to overcome asperity problem during on state. To avoid self-actuation, bumps (0.6um) are used at the bottom side. This electrostatically actuated switch requires a pull-in voltage of 3.1V for 2.4 μm displacement in 67.14 μs time. The proposed switch is analysed in COMSOL software, and its RF characteristics are simulated in HFSS.

This letter presents the fabrication and measurement of a novel loaded line phase shifter design providing four different phase shifts using only two RF MEMS switches. The flexibility of choosing DC or capacitive load depending upon the phase shift required in a single RF MEMS switch makes the phase shifter compact and requires less number of proposed switches. The RF MEMS switch has been designed to provide isolation better than 10 dB in both DC and capacitive states from 16 to 45 GHz. Due to the designed RF MEMS beam switching between DC and capacitive loading, the proposed phase shifter provides a 2-bit phase shift using only two switches. The measured phase shifter has the maximum insertion loss of 0.8 dB with a bandwidth of 8 GHz from 16 to 24 GHz. The return loss is better than 10 dB for all four states. The maximum Root-Mean-Square (RMS) insertion loss error is 0.28 dB, and the phase shift error is 0.98 • . The proposed phase shifter is fabricated using the surface micromachining on the sapphire substrate and occupies an area of 3.931 mm 2 .

Background. The difference in the preclinical curriculum and teaching methodology between European and Southeast Asian countries has a great influence on the process of choosing which education model is predominant and, therefore, students’ opinion on the effectiveness of a preclinical coursework is diverse. The objective of the research was to assess the perception of the preclinical coursework in prosthodontics, conservative dentistry, and endodontics among Indian and North Macedonian students. Materials and Methods. This cross-sectional comparative study was carried out among 3rd-year students, final-year students and interns of dental schools of two respective countries. The data were collected in July 2021 using Google Form, a link to which was sent via available social media platforms. The data obtained were analyzed using SPSSv.21.0 (IBM) software. Results. The data on dental students’ perception of the preclinical coursework were obtained, analyzed, compared, and discussed. A total of 50% of Indian students stated preclinical exercises to be good to get knowledge about treating patients, whereas 47% of North Macedonian students felt the average level of knowledge needed for treating patient. Conclusions. In this study, the majority of the students were in favor of attending the preclinical course and understood its importance for building up their confidence, better understanding of the subject and better patient handling in future dental practice. However, there were different students’ opinions on the course content, its duration, exercises, faculty interaction, helpfulness of theory lectures that evidence essentiality to view dental studies from a student-centered perspective.

This article reports a compact Power Divider design employing a combination of a capacitive load and Defect Grounded Structures (DGS) on GaAs substrate for MMIC technology in the C band. The integration of these two techniques offers a compact power divider with a decrease in quarter-wave transmission line length from λ/4 to λ/16 and harmonic suppression up to 50 GHz. Capacitive loading reduces the size, and DGS improves harmonic suppression and further decreases the size of the structure. The designed power divider is simulated in Ansys HFSS 19.2 and provides a return loss of 25.66 dB, with an insertion loss of 3.01 dB at 5.4 GHz and isolation of 13.37 dB. Isolation is further improved to 30.89 dB using a parallel combination of resistor and capacitor in the isolation network. The prototype of the proposed circuit has been fabricated using RT/duroid ® 5880 as substrate. Measurement results show insertion loss and return loss of 3.02 and 23.46 dB. Isolation of 22.43 dB was achieved. The proposed design provides a size reduction of 73.7% with harmonic suppression up to 10th harmonics by 10 dB, making it suitable for high-performance monolithic microwave integrated circuits (MMIC).

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This paper presents a high performance Dynamic Threshold MOSFET (DTMOS) based low voltage Flip Voltage Follower-Operational Transconductance Amplifier (FVF-OTA). The proposed DTMOS based FVF-OTA combines the low voltage and high transconductance properties of DTMOS with high input impedance and wide output current range characteristics of FVF-OTA. Furthermore, high linearity along with high bandwidth is achieved through DTMOS technique. To show enhancement in the transconductance of the proposed circuit, small signal analysis is carried out. Moreover, Multi Input Single Output (MISO) filter is realized using the proposed DTMOS based FVF-OTA. Simulations of proposed OTA and its MISO filter application are done in Eldospice (Mentor Graphics) in TSMC 0.18 m technology. In the proposed circuit, a transconductance of 314.73 S is achieved at an operating voltage of ± 0.5V and power dissipation of 70.19 W. Moreover, MISO filter realized using the proposed OTA attains a bandwidth of 43.91MHz. To validate the robustness of proposed circuit against variations in temperature and aspect ratios of MOSFETs, temperature and Monte Carlo analysis have been done. Keywords-Dynamic Threshold MOSFET (DTMOS); Flip Voltage Follower (FVF); Operational transconductance amplifier (OTA); Multi Input Single Output (MISO); Monte Carlo analysis.

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