Transmission performance is improving through the use of new modulation formats such as multi-level PSK, OFDM and coherent detection. ROADM, WSS, OXC and optical packet switching have been exploited for the node of fiber ring or mesh network topology to overcome the bottleneck of optical network. This paper reviews recent advances in optical devices for long haul and metropolitan area networks and describes milestones in optical technology. These developments in optical technology allow us to expand the broadband networks. Moreover, the progress made on photonic device performance enhances system performance.
We had the 30-year anniversary since a VCSEL was invented by Kenichi Iga, Tokyo Institute of Technology. We have seen various applications including datacom, sensors, optical interconnects, spectroscopy, optical storages, printers, laser displays, laser radar, atomic clock, optical signal processing and so on. A lot of unique features have been proven, low power consumption, a wafer level testing and so on. In this paper, the brief history and our recent research activities on VCSEL photonics will be reviewed. We present the wavelength engineering of VCSEL arrays for use in high speed short-reach systems, which includes the wavelength integration and wavelength control. The joint research project on ultra-parallel optical links based on VCSEL technologies will be introduced for high speed LANs of 100Gbps or higher. The small footprint of VCSELs allows us to form a densely packed VCSEL array both in space and in wavelength. The wavelength engineering of VCSELs may open up ultra-high capacity networking. Highly controlled multi-wavelength VCSEL array and novel multi-wavelength combiners are developed toward Tera-bit/s-class ultrahigh capacity parallel optical links. In addition, the MEMS-based VCSEL technology enables widely tunable operations. We demonstrated an “athermal VCSEL” with avoiding temperature controllers for uncooled WDM applications. In addition, new functions on VCSELs for optical signal processing are addressed. We present an optical nonlinear phase shifter based on a VCSEL saturable absorber and the tunable optical equalization function. Also, highly reflective periodic mirrors commonly used in VCSELs enables us to manipulate the speed of light. This new scheme provides us ultra-compact intensity modulators, optical switches and so on for VCSEL-based photonic integration. Also, this paper explores plasmonic VCSELs.
The helical structure of progress in microwave and millimeter-wave technologies, with a focus on active device technology and circuit technology, is overviewed with some examples. The position of, and the possibilities for emerging GaN power devices and Si RF devices are described. In addition, as a new trend for methods in global analysis combining electro-magnetic waves and semiconductor devices, FDTD co-simulation is overviewed with the latest example on a 60GHz amplifier module. Finally, the circuit technology in which the helical structure strongly dominates is overviewed. As one of endless targets for microwave circuit technology, the latest design technique for high power efficiency microwave circuits is introduced, in which co-simulation of electro-magnetic waves and semiconductor devices are effectively used.
Electromagnetic wave propagations in a 3-dimensional (3D) left-handed (LH) metamaterial composed of periodic wired metallic spheres are studied numerically. It is shown that the metamaterial supports the dominant 3D LH wave with negative refractive indices. Parametric studies of dependencies of the dispersion characteristics on the unit cell structure are carried out and it is shown that the isotropy can be enhanced by tuning the diagonal wire diameter and the sphere diameters.
There are many challenges inherent in the design of nano-CMOS. This paper describes our recent work relating to the physical design of CMOS circuits. First, in line with variation-aware design, a novel ingenious method of measuring variations in subthreshold characteristics is described. Next, recent RF CMOS issues and approaches to nano-CMOS are discussed. Finally, an on-chip transmission line interconnect developed for global wiring is discussed.
Millimeter-wave communication uses a frequency of at least 30GHz, which is higher than that commonly used for wireless local-area networks (LANs) and cellular phones. Millimeter waves have been used for business communications and radar in luxury cars; however, their use has not yet spread to the general public. In recent years, an increasing amount of research results on millimeter-wave complementary metal-oxide semiconductor (CMOS) integrated circuits has been reported in line with the increasing attention focused on millimeter waves used for high-speed wireless communication, which can realize a communication speed higher than 1Gbps. We discuss the social background behind this recent change in communication technologies and examine the challenges and future prospects of millimeter-wave CMOS integrated circuits.
In this paper, a novel CMOS charge pump with substantially improved immunity to latch-up is presented. By utilizing a dedicated bulk pumping and blocking (DBPB) technique, the proposed charge pump achieves greatly reduced forward voltage of source/drain-substrate junction of transistors, resulting in decreased charge loss and increased latch-up immunity. Comparison results indicated that the maximum bulk forward voltage of the proposed charge pump was less than 0.05V (88% improvement) for zero output current during power-up, and less than 0.12V (88% improvement) regardless of the amount of output current during ordinary pumping operation.
In this paper, we propose a low-cost compensation scheme for IQ imbalance using only one pilot symbol for an orthogonal frequency division multiplexing (OFDM) based digital radio mondiale (DRM)system, planned to operate in FM bands. Since the existing methods require more than one OFDM symbol, this scheme is more efficient in computation, yet performs as well as the existing scheme.
We propose a multilevel transmission technique that employs optical amplitude domain multiplexing. With this technique we can easily increase the capacity of TDM-PON systems based on on-off keying modulation without any loss budget reduction or the need to employ higher frequency drive circuits. We report an experimental result for the proposed multilevel transmission system whose receiver comprises only commercially available electric devices. The experimental result reveals good performance in a quaternary transmission indicating that our technique is suitable for upgrading TDM-PON systems.
This paper presents a highly linear Gilbert cell OTA by cancelling the second order transconductance derivative (gm″) of nMOS transistors near threshold voltage using the technique of multiple gated transistors. This gives rise to 5dB improvement in IIP3 of OTA, using a 0.13µm CMOS technology with 1.2V supply. Simulation results and analytical relations for THD and IIP3 in OTA illustrate the tradeoffs between linearity, bandwidth, and power dissipation. System level simulation of a non-coherent UWB receiver, with this OTA as a Gm-C integrator in receiver structure, illustrates an improvement of BER from 3e-2 to 1e-3. The power consumption, IIP3, and transconductance in OTA are 0.62mW, 20.5dBm, and 156µA/V, respectively.
The method of physical optics is extended for wedge diffraction. The classical integral of physical optics is taken into account for the diffraction problem of plane waves by a conducting half-plane. The integral is decomposed according to the transmitted and reflected scattered waves. The sinusoidal term in the integrand is rewritten by considering the fact that the half-plane is a special case of the wedge. Two cases of soft and hard surfaces are examined and the uniform diffracted waves are obtained by the asymptotic evaluation of the integrals. The results are compared with the literature numerically.
We characterize the properties of one- and two-dimensional transmission lines periodically loaded with electronic switches, for use in managing amplitude and propagation orientations of pulses traveling on the lines. The detection of the input voltage level is successfully demonstrated experimentally using the test switch line. Moreover, the orientation of pulse propagation is controllable in a two-dimensional switch line.
This paper presents a novel technique to determine image distortion properties, such as translation, scale, rotation and skew properties, by only using its moments. The properties are retrieved by solving the algebraic relationships between moment functions of original and geometrically distorted images. These properties, to the best of our knowledge, have yet to be presented in any papers. The derived distortion properties are experimentally validated using randomly scaled, rotated and skewed images. Promising results are produced from these experiments.
The paper presents a full digitized approach for the pulse compression implementation in chirp radars. The emphasis is to cancel the quadratic phase term of the echo using a coordinate rotation digital computer (CORDIC). This approach has been implemented on a field programmable gates array (FPGA) and the compressed output peak is 100dB larger than the noise.
In this paper a limit cycle analysis of attitude control for a launch vehicle is described. PWM signals from PD control laws are applied to attitude control and time delay in solenoid valve is considered. A novel phase plane method is proposed for describing characteristics of limit cycle. Important characteristics of resultant limit cycle such as frequency, amplitude, maximum rate, and duty ratio could be analytically solved by the proposed phase plane method.
This paper presents a novel electronic travel aid, called iSONIC, which can help a visually impaired person walk around more safely. Attached to a conventional white cane, the iSONIC detects obstacles at head-height that cannot be covered by a traditional cane and gives warnings in the forms of vibration or sound to avoid dangerous situations. We developed an algorithm to restrict the sensing range to reduce confusing and unnecessary detections and a method to remove the sensing errors due to the impact of ground tapping. In addition to obstacle detection, the iSONIC give information of object color and the environmental brightness when the user wants to know.