The Ant Lion Optimizer

Grasshopper Optimisation Algorithm

International Technology Roadmap for Semiconductors 2003の要求清浄度について － シリコンウエハ表面と雰囲気環境に要求される清浄度, 分析方法の現状について －

This Review covers the state-of-the-art technologies on photonics-based terahertz communications, which are compared with competing technologies based on electronics and free-space optical communications. Future prospects and challenges are also discussed. Almost 15 years have passed since the initial demonstrations of terahertz (THz) wireless communications were made using both pulsed and continuous waves. THz technologies are attracting great interest and are expected to meet the ever-increasing demand for high-capacity wireless communications. Here, we review the latest trends in THz communications research, focusing on how photonics technologies have played a key role in the development of first-age THz communication systems. We also provide a comparison with other competitive technologies, such as THz transceivers enabled by electronic devices as well as free-space lightwave communications.

/pdf/advances-in-terahertz-communications-accelerated-by-t151adrqkd.pdf

Advances in terahertz communications accelerated by photonics

Science and technologies based on terahertz frequency electromagnetic radiation (100 GHz–30 THz) have developed rapidly over the last 30 years. For most of the 20th Century, terahertz radiation, then referred to as sub-millimeter wave or far-infrared radiation, was mainly utilized by astronomers and some spectroscopists. Following the development of laser based terahertz time-domain spectroscopy in the 1980s and 1990s the field of THz science and technology expanded rapidly, to the extent that it now touches many areas from fundamental science to 'real world' applications. For example THz radiation is being used to optimize materials for new solar cells, and may also be a key technology for the next generation of airport security scanners. While the field was emerging it was possible to keep track of all new developments, however now the field has grown so much that it is increasingly difficult to follow the diverse range of new discoveries and applications that are appearing. At this point in time, when the field of THz science and technology is moving from an emerging to a more established and interdisciplinary field, it is apt to present a roadmap to help identify the breadth and future directions of the field. The aim of this roadmap is to present a snapshot of the present state of THz science and technology in 2017, and provide an opinion on the challenges and opportunities that the future holds. To be able to achieve this aim, we have invited a group of international experts to write 18 sections that cover most of the key areas of THz science and technology. We hope that The 2017 Roadmap on THz science and technology will prove to be a useful resource by providing a wide ranging introduction to the capabilities of THz radiation for those outside or just entering the field as well as providing perspective and breadth for those who are well established. We also feel that this review should serve as a useful guide for government and funding agencies.

https://iopscience.iop.org/article/10.1088/1361-6463/50/4/043001/pdf

The 2017 terahertz science and technology roadmap

A systematic approach to designing high frequency and high power oscillators using activity condition is introduced. This method finds the best topology to achieve frequencies close to the fmax of the transistors. It also determines the maximum frequency of oscillation for a fixed circuit topology, considering the quality factor of the passive components. Using this technique, in a 0.13 μm CMOS process, we design and implement 121 GHz and 104 GHz fundamental oscillators with the output power of -3.5 dBm and -2.7 dBm, respectively. Next, we introduce a novel triple-push structure to realize 256 GHz and 482 GHz oscillators. The 256 GHz oscillator was implemented in a 0.13 μm CMOS process and the output power of -17 dBm was measured. The 482 GHz oscillator generates -7.9 dBm (0.16 mW) in a 65 nm CMOS process.

/pdf/high-power-terahertz-and-millimeter-wave-oscillator-design-a-2697zxm3zv.pdf

High Power Terahertz and Millimeter-Wave Oscillator Design: A Systematic Approach

Nonlinear transmission lines (NLTL) are used for pulse shaping. We developed the theory of pulse propagation through the NLTL. The problem of a wide pulse degenerating into multiple pulses rather than a single pulse is solved by using a gradually scaled NLTL. We exploit certain favorable properties of accumulation-mode MOS varactors to design an NLTL that can simultaneously sharpen both rising and falling edges. There is a good agreement among the theory, simulations, and measurements.

/pdf/nonlinear-transmission-lines-for-pulse-shaping-in-silicon-3vjm0x6yu2.pdf

Nonlinear transmission lines for pulse shaping in silicon

Power quality and voltage control are among the most important aspects of the grid-connected power converter operation under faults. Nonsinusoidal current may be injected during unbalanced voltage sag, and active or/and reactive power may include double frequency content. This paper introduces a novel control strategy to mitigate the double grid frequency oscillations in the active power and dc-link voltage of the two-stage three-phase grid-connected photovoltaic (PV) inverters during unbalanced faults. With the proposed control method, PV inverter injects sinusoidal currents under unbalanced grid faults. In addition, an efficient and easy-to-implement current limitation method is introduced, which can effectively limit the injected currents to the rated value during faults. In this case, the fault-ride-through operation is ensured, and it will not trigger the overcurrent protection. A non-maximum power point tracking (non-MPPT) operation mode is proposed for the dc–dc converter. The mode is enabled under severe faults when the converter cannot handle the maximum PV power. Finally, experimental validation is provided by implementing a method in an experimental setup, including a 2 kW PV inverter.

/pdf/control-strategy-for-three-phase-grid-connected-pv-inverters-4ezf192tah.pdf

Control Strategy for Three-Phase Grid-Connected PV Inverters Enabling Current Limitation Under Unbalanced Faults

Schottky-barrier diodes (SBD's) fabricated in CMOS without process modification are shown to be suitable for active THz imaging applications Using a compact passive-pixel array architecture, a fully-integrated 280-GHz 4 × 4 imager is demonstrated At 1-MHz input modulation frequency, the measured peak responsivity is 51 kV/W with ±20% variation among the pixels The measured minimum NEP is 29 pW/Hz1/2 Additionally, an 860-GHz SBD detector is implemented by reducing the number of unit cells in the diode, and by exploiting the efficiency improvement of patch antenna with frequency The measured NEP is 42 pW/Hz1/2 at 1-MHz modulation frequency This is competitive to the best reported performance of MOSFET-based pixel measured without attaching an external silicon lens (66 pW/Hz1/2 at 1 THz and 40 pW/Hz1/2 at 650 GHz) Given that incorporating the 280-GHz detector into an array increased the NEP by ~ 20%, the 860-GHz imager array should also have the similar NEP as that for an individual detector The circuits were utilized in a setup that requires neither mirrors nor lenses to form THz images These suggest that an affordable and portable fully-integrated CMOS THz imager is possible

/pdf/active-terahertz-imaging-using-schottky-diodes-in-cmos-array-1lipxoxjoj.pdf

Active Terahertz Imaging Using Schottky Diodes in CMOS: Array and 860-GHz Pixel

A high-power broadband 260-GHz radiation source using 65-nm bulk CMOS technology is reported. The source is an array of eight harmonic oscillators with mutual coupling through four 130-GHz quadrature oscillators. Based on a novel self-feeding structure, the harmonic oscillator simultaneously achieves the optimum conditions for the fundamental oscillation and the 2nd-harmonic generation. The signals at 260 GHz radiate through eight on-chip slot antennas, and are in-phase combined inside a hemispheric silicon lens attached at the backside of the chip. Similar to the laser pulse-driven photoconductive emitter in many THz spectrometers, the radiation of this source can also be modulated by narrow pulses generated on chip, which achieves broad radiation bandwidth. Without modulation, the chip achieves a measured continuous-wave radiated power of 1.1 mW, and an EIRP of 15.7 dBm. Under modulation, the measured bandwidth of the source is 24.7 GHz. This radiator array consumes 0.8-W DC power from a 1.2-V supply.

Ehsan Afshari

Papers

High Power Terahertz and Millimeter-Wave Oscillator Design: A Systematic Approach

Nonlinear transmission lines for pulse shaping in silicon

Control Strategy for Three-Phase Grid-Connected PV Inverters Enabling Current Limitation Under Unbalanced Faults

Active Terahertz Imaging Using Schottky Diodes in CMOS: Array and 860-GHz Pixel

A CMOS High-Power Broadband 260-GHz Radiator Array for Spectroscopy