A miniaturized, broadband quasi-Yagi antenna utilizing a modified ultra-wideband microstrip-to-coplanar stripline (MS-to-CPS) balun is proposed. Excellent broadband phase and amplitude balance is possible due to the ultra-wideband MS-to-CPS balun based on field and impedance matching concept. The implemented antenna provides very wide bandwidth from 7 to 15.1GHz (73.3%). The gain of the antenna is from 3.7 to 5.5dBi, the front-to-back ratio is more than 10dB, and the nominal radiation efficiency is about 94%.
This paper reports on the design of a low-power biostimulator, capable of generating stimulus pulses with arbitrary wave shapes and programmable amplitude and timing. Designed based on a modular architecture with programmable stimulation details, this system can be used in a wide variety of applications. The system complies with basic requirements for biomedical stimulation systems such as small physical size, serial data communication with external setup, and low-power consumption. It also performs basic functions such as generating bi-phasic pulses, single/train pulses, and residual charge cancellation. Clock gating, operation with external timing, and shared resources are used among the main techniques to significantly reduce the power consumption of the system. To wirelessly interface with the external setup, a BPSK demodulator and clock recovery circuit is used which exhibit 100% data-rate-to-carrier-frequency ratio and consumes as low as 120µW at 2.5Mbps. The system was designed and simulated in a 0.18-µm standard CMOS technology, prototyped for functional verifications, and successfully tested.
We propose a microelectromechanical system (MEMS) mirror design, which is suitable for use in a flexible-grid wavelength selective switch (WSS). In the flexible grid operation with a conventional MEMS-based WSS, the diffraction loss at the inter-mirror gap regions caused a large ripple in the transmission spectra. On the other hand, the newly introduced slot structures in each mirror can reduce the ripples by intentionally attenuating the light on the mirrors to equalize the reflectance of the entire mirrors. We optimize the slot structure aiming for the flexible-grid WSS operation with a bandwidth-granularity of 12.5GHz. The ripples are successfully reduced to below 0.004dB with a loss penalty of only 1.05dB.
In this study, a photosensitive chaotic circuit suitable for an integrated circuit with light controllability is proposed. The circuit consists of a photo sensor, two pairs of clock switches and capacitors and two nonlinear function blocks. After modeling the photodiode by MEDICI program, the full circuit was simulated with SPICE using a 0.35µm CMOS process parameters technology. By varying the light intensity on the photodiode, chaotic dynamics such as time series and bifurcation diagram were analyzed. We confirmed that chaotic behaviors of the circuit can be controlled according to light intensity.
In this paper, the proposed shunt regulator is presented. Compared with a series voltage regulator, the shunt voltage regulator gives wideband power supply rejection (PSR) and fast transient response at the expense of large quiescent current. In this paper, a novel shunt regulator architecture is proposed to achieve the genuine characteristic of a shunt regulator with small quiescent current. The proposed shunt regulator transient response is 3.98µsec over full load current rising step and it is at least 3.5 times faster than series regulator. PSR characteristic of the proposed shunt regulator shows -22.4dB up to 200kHz.
This paper deals with the experimental transmission of analog TV-signal in a fiber-radio scheme using a microwave photonic filter. For that purpose, filtering of a microwave band-pass window located at 2.8GHz is obtained by the interaction of an externally modulated multimode laser diode emitting at 1.5µm associated to the chromatic dispersion parameter of an optical fiber. Transmission of TV-signal coded on the microwave band-pass window is achieved over an optical link of 20.70Km. Demodulated signal is transmitted via radiofrequency using printed antennas. This communication scheme has a potential application in the field of FTTx network architectures.
A high-performance operational transconductance amplifier (OTA) is proposed. In order to increase DC gain, gain bandwidth, and the slew rate under low standby quiescent current, the proposed OTA has the dynamic output current scaling and class AB operation. Under the condition of 250µA quiescent current and a 30pF load capacitance with a step voltage from 1.2 to 1.5V at a rise time of 1nsec in a unit gain configuration, HSPICE simulation results are presented to show a higher DC gain, gain bandwidth and slew rate than conventional OTAs.