This paper presents a comprehensive analysis of Class-E series-tuned radio-frequency power amplifiers (RFPAs), focusing on their design and optimization for high efficiency and performance. However, achieving optimal performance involves navigating trade-offs among efficiency, bandwidth, harmonic suppression, output power capability, and device stress. This work examines the trade-offs involved in the series-tuned (𝐿𝑠−𝐶𝑠) network and establishes the bounds for its quality factor using computer-aided harmonic balance (HB) simulations. Additionally, it explores optimal harmonic termination strategies to enhance the performance and efficiency of the design. Finally, a novel methodology using harmonic termination is proposed, simplifying the design process by eliminating the need for traditional load-pull extraction methods.@en

Acousto-Optical Tunable Filters (AOTFs) are a promising technology, exceptionally suited for advanced applications in spectroscopy and imaging across various scientific fields, including space exploration. This is due to their flexibility and high-speed functionality for precise wavelength selection via periodic modulation of the crystal’s refractive index using sound waves. These AOTFs are in turn driven by Radio Frequency (RF) signals through a transducer creating sound waves inside the crystal. This work presents a detailed comparison of three distinct topologies of Radio Frequency Power Amplifiers (RFPAs) for driving these AOTFs within the 30 to 300 MHz frequency range. The analysis focuses on three critical parameters: efficiency, bandwidth, and linearity, which are essential for optimizing the performance of AOTFs. By evaluating the trade-offs among these parameters, this research aims to identify the most effective design approach for RFPAs in this application context.@en

This paper presents a new architecture of a compact multimode FMCW radar for general purpose short-range applications. The radar can operate in CW as well as in FMCW modes. The transmitted RF frequency or frequency range can be arbitrarily selected using an inbuilt SPI control over 2.25-2.50 GHz with a frequency resolution of at least 100 kHz. A modified VCO-PLL loop with a stable reference source of 10 MHz improves the frequency stability. Other than the audio signal generator, all modules like RF blocks, base-band block DC power management block, and control and synchronization and data acquisition blocks are integrated into a single module using a three-layer PCB configuration. Fabrication and measurement of the radar unit in both the modes are presented.

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An improved design of a cavity-backed slot ring antenna is presented. The antenna maintains its radiation characteristics and good impedance matching over at least 10 % frequency band. Over the band, the antenna does not show any beam tilt. Two higher order resonant modes are used to obtain high gain. The improved antenna characteristics is obtained by elevating a part of the top cavity plate containing the ring slot. A prototype antenna is designed and fabricated for 2.25-2.5 GHz short-range indoor radar applications. The antenna provides a measured gain of 7±0.5dBi over the entire band. The overall dimension of the antenna is 0.64λ0 × 0.64λ0 × 0.08 λ0, λ0 being the free space wavelength at the mid-band frequency. Design guidelines are provided for the frequency scaling.

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A non-coherent passive six-port receiver system is presented for accurate amplitude, phase and frequency measurement of a RF signal. The system uses the six-port network and a new wideband phase delay line with known phase profile. The phase delay unit uses a number of openstubs connected to a microstrip line. Detail design steps of the phase delay line is presented. The whole receiver is fabricated in PCB technology. No local oscillator or DC biasing are used. Thus, it is an all-passive system, which does not require any power source. It can be used as a real time and fast demodulator for both analog and digital signals.

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Reports on initiatives by the IEEE to provide wireless communications and access to the Internet for educational purposes. As the world's largest technical professional organization dedicated to advancing technology for the benefit of humanity, the IEEE has long been actively involved in outreach activities that bridge the digital divide. We, the members of the IEEE Antennas a n d Propagation Society (APS) and IEEE Microwave Theory and Technique s Society (MTT-S) Joint Student Branch Chapter (SBC) of the Indian Institute of Technology (IIT), Kharagpur (AP-MTT-SBC ITT Kharagpur), were also involved in a project to bridge the digital divide by exposing high school students to the basics of wireless communication and the Internet of Things (IoT). For four days (21-24 December 2020), the SBC ran outreach workshops for rural high school students. The main objective of the outreach workshop program was to acquaint as many students as possible who live in remote areas and lack financial and technical resources.

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This paper presents a compact continuous wave Doppler radar architecture at 2.4 GHz. The system provides a low-cost solution to remotely monitor vibrations of any object. In the RF system, two separate antennas are used for the transmitter and receiver. The receiver works in homodyne mode. A single microwave oscillator is used to transmit continuous wave signal as well as the synchronized local oscillator for the receiver. An opamp base band electronics separate the small receiver output signal from a large dc offset due to homodyne operation. In comparison to other approaches, number of components are minimized.

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