Voltage-controlled Oscillator (VCO) is a prominent part that has been used to generate a stable frequency for the high-frequency transceiver system. This survey encompasses a comparative analysis of two commonly used VCO architectures: the Ring VCO and LC-VCO. The Ring VCO has been constructed with the collection of ring delay cells. Moreover, the LC-VCO utilizes inductors, capacitors, fine-tuning circuits, coarse-tuning circuits to generate frequency. Furthermore, this study investigates an in-depth exploration of VCO structures, operational principles, advantages, limitations, and performance metrics. In addition, it evaluates performance parameters, including operating frequency range, phase noise, figure of merit, and tuning techniques. This research suggests that based on the application and its requirements, the VCO performance parameters need to be varied. This survey employs diverse types of VCO, and its design methods. Implications for future research and study of VCO design and integration are discussed.

A simple new phase frequency detector (PFD) is presented in this paper. This PFD use only 10 transistors, whereas a conventional PFD uses 54 transistors. It has been observed that the proposed PFD could operate up to frequencies about 4.6 times higher than that by conventional PFD. It has also been observed that the power dissipation is reduced by 99%. In addition to these, area of the circuit has been reduced up to 73% when compared with conventional PFD. The phase noise of designed PFD has been reduced to - 133.4 dBc/Hz. Prototype has been designed in Cadence virtuoso environment and implemented using GPDK090 library of 180nm technology with a supply voltage of 1.8V. The reset process has been completely removed in this design thereby eliminating the blind zone and speeding up the acquisition process. The design has been proposed for high speed, low power and low jitter applications

Underwater wireless communication (UWC) means the transmission of data using wireless channels through the underwater, i.e. radio frequency waves (RF), acoustic waves and optical waves in an unguided water environment. In this review article we focus on underwater optical wireless communications (UWOCs) using optical waves as transmission medium. UWOCs have a much higher communication frequency and therefore a much higher data rate compared to RF and acoustic counter-parts. Due to this high-speed data transfer advantage, UWOC has been very attractive over the past few years. Many applications have been proposed in UWOC systems for protection of the environment, underwater exploration, emergency alerts and military operations etc. However, underwater channels also suffer from extreme absorption and dispersion. In recent years, a variety of innovative methods of network architecture have been developed to meet these technological challenges, which are different from standard terrestrial, open space optical communications. In this article we give a detailed overview of various research activities on UWOC.

This paper aims to explore diverse landscape of Phase Locked Loops (PLLs), offering a comprehensive categorization and in-depth analysis of their underlying working principles. Addressing the challenges of differentiation within this complex field, the review meticulously examines a curated selection of prominent research papers and articles encompassing a diverse range of PLL types. The taxonomy, meticulously constructed based on architectural and functional criteria, classifies various PLL categories precisely, elucidating the modifications implemented for optimal performance. To further enhance comprehension, a detailed block diagram architecture of a typical PLL system is presented alongside a comprehensive table showcasing operational parameters across different categories. The review presents illustrative graphs of various operational parameters, which include Power Consumption, Phase Noise, Output Frequency, Area, Figure of Merit(FOM), and lock time, enabling the visualization of trends over time. This work provides a significant contribution thereby assisting the budding researchers with insights and compressions.

Two novel phase frequency detectors PFD1 and PFD2 have been proposed in this paper. PFD1 has been designed with 15 transistors while PFD2 with 8 transistors. It has been observed that both these PFDs could operate up to frequencies three to five times higher than that of conventional PFD. It has also been observed that the power dissipation is reduced by 80.3% and 99.2 % in PFD1 and PFD2 respectively. In addition to these, area of the circuit has been reduced up to 64.9 % for PFD1 and up to 81.4 % for PFD2 when compared with conventional PFDs. The phase noise also has been reduced to - 161.8 dBc/Hz and -142.1 dBc/Hz for PFD1 and PFD2 respectively. Prototype has been designed in Cadence virtuoso environment and implemented using GPDK090 library of 180 nm technology with a supply voltage of 1.8 V. The reset process has been completely removed in both the designs thereby eliminating the blind zone and speeding up the acquisition process. Both the designs have been proposed for high speed, low power and low jitter applications.