Inn-Yeal Oh

A 2.16 mW Low Power Digitally-Controlled Variable Gain Amplifier

A low power digitally-controlled CMOS variable gain amplifier (VGA) was fabricated in a TSMC 0.18 ¿m CMOS technology. By extending the transconductor operation range from saturation mode for high gain to triode mode for low gain, the proposed VGA can obtain a wide gain range with low power dissipation. The power consumption of the proposed VGA is as small as 2.16 mW while keeping a wide gain range of 53 dB. The proposed VGA has a controlled gain from -22 dB to 31 dB with 1 dB steps. When the proposed VGA was set to a maximum gain, the total harmonic distortion (THD) and the 3 dB bandwidth are -48 dB and at least 65 MHz, respectively.

Concurrent dual-channel RF transceiver module with diversity for 802.11p WAVE

In this paper, we present a prototype of a concurrent dual-channel RF transceiver module with diversity for wireless access in vehicular environment (WAVE) system. Two parallel RF paths are designed for concurrent communication. At each moment of time, both transceivers in the RF paths are simultaneously operated as transmitters or receivers. In each path, two antennas are connected with a diversity switch for pure selection diversity. The implemented RF module is evaluated by measuring the transmission spectrum in the transmitting mode. The measured spectrum of the 10 MHz channel bandwidth at the center frequency of 5.86 GHz satisfies the required transmission spectrum mask of Class C in IEEE 802.11p. Moreover, when the module works as a receiver, we can confirm the packet error rate (PER) by monitoring the number of received packets in the measurement system.

60GHz Double-balanced drain-pumped up-conversion mixer using 90nm CMOS

A new type of drain-pumped mixer is proposed for a 60 GHz direct up-conversion using a standard 90nm CMOS process in this paper. Because no stacks are needed for the architecture, a high conversion gain (CG) thanks to high trans-conductance (gm) can be achieved while consuming low power. By configuring a balanced architecture for LO-to-RF isolation, the proposed mixer demonstrates CG of -5.1dB with a reasonable 0dBm LO power while maintaining low power dissipation of 16.3mW. Its LO-to-RF isolation is better than 30dB and size is only 0.35mm2.

Design of a reconfigurable phase controller for focused ultrasound therapeutic device

The use of focused ultrasound in non-invasive therapeutic applications can achieve energy concentration at a target point. Depending on the purpose of use, devices should have reconfigurable focal depths by controlling the phase or time delay of the signal applied to the transducer array. In this study, a phase controller that consists of a flash ADC, a resistor-capacitor bank phase shifter, a variable gain amplifier, and a 0°/180° phase shifter is proposed. The phase resolution has 11.25°. With every 90mV increase in input voltage, the phase of the signal is changed as much as the step of resolution, which can cover the full range from 0° to 360°. The proposed phase controller is implemented in 0.18um CMOS technology and the chip size is 1.11×0.99mm2.

A study on the beamforming system with reconfigurable focusing depth for ultrasound-enhanced thrombolysis

In order to dissolve clots within blood vessels located in various parts of the human body with one sonothrombolysis application, the device employed should be able to control the focal depth where acoustic energy is focused. This paper presents such an ultrasound beamforming system with reconfigurable focal depth. It consists of an annular piezoelectric micromachined ultrasonic transducer (pMUT) array of 1 cm radius, and a beamforming unit that is composed of an ARM processor and a driving circuit. The measured peak intensity at the focal point of 13 mm is 1.35 W/cm2, and the average intensity of the -3 dB focal dimension from the peak intensity is 933 mW/cm. The proposed system operating at 1.21 MHz could be used for ultrasound-accelerated thrombolysis with an intensity that is above typical diagnostic levels at the focusing point, and also with a reconfigurable focusing depth.

Energy and thermal distribution under the skin during ultrasound power transfer

Energy distribution under the human skin during ultrasound power transfer using a 15×15 MEMS transducer array with 2.2 MHz driving frequency is presented in this paper. When the surface pressure of the array element is 96 kPa, intensity at 2 mm under the skin is 0.96 W/cm2; intensity increases to 24 W/cm2 when the surface pressure increases to 0.48 MPa. In other words, the simulation results show that the larger the surface pressure, the larger the intensity. The simulated and the measured power density values at 7 mm in the vertical direction of the transducer surface in degassed water are 96.72 mW/cm2 and 94.08 mW/cm2, respectively. Temperature change due to ultrasound radiation on the skin is discussed, and the feasibility of ultrasonic power transfer for implantable medical devices specially implanted just underneath the skin is presented.