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Author

Shoji Otaka

Bio: Shoji Otaka is an academic researcher from Toshiba. The author has contributed to research in topics: Signal & Amplifier. The author has an hindex of 22, co-authored 136 publications receiving 1941 citations.
Topics: Signal, Amplifier, Voltage, CMOS, Phase-locked loop


Papers
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Journal ArticleDOI
TL;DR: In this article, the authors presented a 950-MHz wireless power transmission system and a high-sensitivity rectifier circuit for ubiquitous sensor network tags, which offers a battery-life-free sensor tag by recharging the output power of a base station into a secondary battery implemented with the tag.
Abstract: This paper presents a 950-MHz wireless power transmission system and a high-sensitivity rectifier circuit for ubiquitous sensor network tags. The wireless power transmission offers a battery-life-free sensor tag by recharging the output power of a base station into a secondary battery implemented with the tag. For realizing the system, a high-sensitivity rectifier with dynamic gate-drain biasing has been developed in a 0.3-/spl mu/m CMOS process. The measurement results show that the proposed rectifier can recharge a 1.2-V secondary battery over -14-dBm input RF power at a power conversion efficiency of 1.2%. In the proposed wireless system, this sensitivity corresponds to 10-m distance communication at 4-W output power from a base station.

414 citations

Patent
14 Sep 1995
TL;DR: In this paper, a frequency conversion apparatus comprising a sampling circuit for receiving a first intermediate frequency signal extracted from an input signal and having a predetermined intermediate frequency and a predetermined band width was presented.
Abstract: A frequency conversion apparatus comprising a sampling circuit for receiving a first intermediate frequency signal extracted from an input signal and having a predetermined intermediate frequency and a predetermined band width and sampling the first intermediate frequency signal in accordance with a predetermined sampling frequency signal, to output a second intermediate frequency signal, and a sampling signal generator for outputting the sampling frequency signal to the sampling circuit, the sampling frequency signal having a frequency determined so that an integer multiple of not less than three times the sampling frequency is outside a frequency range of the input signal.

89 citations

Journal ArticleDOI
07 Feb 2000
TL;DR: In this article, a linear-in-dB variable-gain amplifier (VGA) using a pre-distortion circuit to generate the gain-control signal is fabricated in a BiCMOS process with f/sub T/=20 GHz.
Abstract: A linear-in-dB variable-gain amplifier (VGA) using a pre-distortion circuit to generate the gain-control signal is fabricated in a BiCMOS process with f/sub T/=20 GHz. The VGA comprises two cascaded stages of signal-summing VGA and has a variable-gain range of over 70 dB. It can operate at up to 500 MHz and dissipates 36 mW from a 3-V supply. A noise figure of below 5 dB and IIP3 of over -38 dBm at 43-dB gain were obtained. The VGA achieved a gain error of less than 2 dB over 70-dB gain range, and it occupies approximately 1 mm/sup 2/. The VGA is applicable to future code division multiple access (CDMA) receivers.

85 citations

Proceedings ArticleDOI
29 Aug 2005
TL;DR: In this paper, a high-sensitivity rectifier was fabricated in a 0.3 /spl mu/m CMOS technology, which can rectify an RF signal less than the NMOS threshold voltage by using a bias voltage between the gate and the drain terminals of a transistor.
Abstract: A high-sensitivity rectifier is fabricated in a 0.3 /spl mu/m CMOS technology. The circuit can rectify an RF signal less than the NMOS threshold voltage by using a bias voltage between the gate and the drain terminals of a transistor. The IC achieves a 950 MHz signal rectification over -14 dBm corresponding to 10 m-distance communication and recharges a 1.2 V secondary battery.

67 citations

Journal ArticleDOI
TL;DR: In this article, a 7 GHz low-noise amplifier (LNA) was designed and fabricated using 0.25/spl mu/m CMOS technology, and a cascode configuration with a dual-gate MOSFET and shielded pads was adopted to improve the gain and the noise performance.
Abstract: A 7-GHz low-noise amplifier (LNA) was designed and fabricated using 0.25-/spl mu/m CMOS technology. A cascode configuration with a dual-gate MOSFET and shielded pads were adopted to improve the gain and the noise performance. The effects of the dual-gate MOSFET and the shielded pads are discussed quantitatively. An associated gain of 8.9 dB, a minimum noise figure of 1.8 dB, and an input-referred third-order intercept point of +8.4 dBm were obtained at 7 GHz. The LNA consumes 6.9 mA from a 2.0-V supply voltage. These measured results indicate the feasibility of a CMOS LNA employing these techniques for low-noise and high-linearity applications at over 5 GHz.

60 citations


Cited by
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Journal ArticleDOI
TL;DR: An RF-DC power conversion system is designed to efficiently convert far-field RF energy to DC voltages at very low received power and voltages and is ideal for use in passively powered sensor networks.
Abstract: An RF-DC power conversion system is designed to efficiently convert far-field RF energy to DC voltages at very low received power and voltages. Passive rectifier circuits are designed in a 0.25 mum CMOS technology using floating gate transistors as rectifying diodes. The 36-stage rectifier can rectify input voltages as low as 50 mV with a voltage gain of 6.4 and operates with received power as low as 5.5 muW(22.6 dBm). Optimized for far field, the circuit operates at a distance of 44 m from a 4 W EIRP source. The high voltage range achieved at low load current make it ideal for use in passively powered sensor networks.

766 citations

Journal ArticleDOI
TL;DR: The idea of wireless power transfer (WPT) has been around since the inception of electricity and Nikola Tesla described the freedom to transfer energy between two points without the need for a physical connection to a power source as an?all-surpassing importance to man? as discussed by the authors.
Abstract: The idea of wireless power transfer (WPT) has been around since the inception of electricity. In the late 19th century, Nikola Tesla described the freedom to transfer energy between two points without the need for a physical connection to a power source as an ?all-surpassing importance to man? [1]. A truly wireless device, capable of being remotely powered, not only allows the obvious freedom of movement but also enables devices to be more compact by removing the necessity of a large battery. Applications could leverage this reduction in size and weight to increase the feasibility of concepts such as paper-thin, flexible displays [2], contact-lens-based augmented reality [3], and smart dust [4], among traditional point-to-point power transfer applications. While several methods of wireless power have been introduced since Tesla?s work, including near-field magnetic resonance and inductive coupling, laser-based optical power transmission, and far-field RF/microwave energy transmission, only RF/microwave and laser-based systems are truly long-range methods. While optical power transmission certainly has merit, its mechanisms are outside of the scope of this article and will not be discussed.

745 citations

Journal ArticleDOI
TL;DR: In this article, the authors summarized recent energy harvesting results and their power management circuits and showed that rectification and DC-DC conversion are becoming able to efficiently convert the power from these energy harvesters.
Abstract: More than a decade of research in the field of thermal, motion, vibration and electromagnetic radiation energy harvesting has yielded increasing power output and smaller embodiments. Power management circuits for rectification and DC–DC conversion are becoming able to efficiently convert the power from these energy harvesters. This paper summarizes recent energy harvesting results and their power management circuits.

737 citations

Proceedings Article
01 Jan 2009
TL;DR: This paper summarizes recent energy harvesting results and their power management circuits.
Abstract: More than a decade of research in the field of thermal, motion, vibration and electromagnetic radiation energy harvesting has yielded increasing power output and smaller embodiments. Power management circuits for rectification and DC-DC conversion are becoming able to efficiently convert the power from these energy harvesters. This paper summarizes recent energy harvesting results and their power management circuits.

711 citations