Junichi Kodate

2-GHz RF front-end circuits in CMOS/SIMOX operating at an extremely low voltage of 0.5 V

2-GHz RF front-end circuits [low noise amplifier (LNA), mixer, and voltage-controlled oscillator (VCO)] enabling 0.5-V operation are presented. The circuits were fabricated by 0.2-/spl mu/m fully depleted CMOS/SIMOX technology. The mixer has an LC-tuned folded structure to avoid stacking transistors. Undoped-channel MOSFETs are used in the VCO core and in a complementary source follower as output buffers for the mixer and the VCO. The noise figures of 3.5 dB (LNA) and 16.1 dB (mixer), IIP3 of -6-dBm (mixer), and phase noise of -110 dBc/Hz at 1-MHz offset (VCO) are achieved at a supply voltage of 1 V. They dissipate 2 mW (LNA), 4 mW (mixer), and 3 mW (VCO) at 0.5.

Novel Structure and Fabrication Process for Integrated RF Microelectromechanical-System Technology

This paper describes a novel structure and fabrication process for the integration of several types of RF microelectromechanical-system (MEMS) device, such as switches and varactors having different structures. It also describes an encapsulation technique suitable for the integrated devices to protect movable parts during packaging. An adaptable multilayer structure and its fabrication process, which includes planarization with photosensitive polyimide, are proposed for integration. A capsule structure fabricated using spin-coating film transfer and hot-pressing technology is also proposed for protection. Several types of RF MEMS device were simultaneously fabricated on the same substrate using these techniques. The results confirm that these techniques will pave the way for the development of single-chip RF transceivers with integrated RF MEMS devices.

Macromodels in the frequency domain analysis of microwave resonators

This paper describes a 1-V operation Bluetooth RF transceiver in 0.2-/spl mu/m CMOS SOI. The transceiver integrates a radio-frequency transmit/receive switch, an image-reject mixer, a quadrature demodulator, g/sub m/-C filters, an LC-tank voltage-controlled oscillator, a phase-locked loop synthesizer, and a power amplifier. The phase shifter in the quadrature demodulator is tuned dynamically to track the carrier-frequency drift allowed in the Bluetooth specification. The g/sub m/ cell in the filters uses depletion-mode pMOS transistors. In order to achieve 1-V operation, LC-tuned-folded and transistor-current-source-folded circuits are used in the RF and IF building blocks, respectively. In order to minimize power consumption, the current flowing through the circuit is optimally shared between the folded stages. A tuning circuit for the g/sub m/-C filters and a bias generation circuit ensure stable transceiver performance. The transceiver shows -77-dBm sensitivity at 0.1% bit error rate and consumes 33 and 53 mW from 1 V in the transmit and receive modes, respectively.

Practical High-Resistivity Silicon-on-Insulator Solution for Spiral Inductors in Radio-Frequency Integrated Circuits

The effect of high-resistivity (high-R) silicon-on-insulator (SOI) substrates on spiral inductors in radio-frequency integrated circuits (RF ICs) has been investigated by experiment and simulation. The effect of the high-R substrates on the spiral inductors saturates at a resistivity above 2–3 kΩ cm, and the resistivity must be maintained high with a thickness of about 300 µm. The resistivity dependence of the high-R effect can be explained with a dielectric loss mechanism in silicon substrates. The thickness criterion of the effect can be explained with an inductor model that includes magnetically induced current in a ground plane. On the basis of experimental results and discussion, we conclude that a commercially available high-R wafer with carefully designed back-end process is sufficient for obtaining the maximum effect of high-R substrates.

Suppression of Substrate Crosstalk in Mixed-Signal Complementary MOS Circuits Using High-Resistivity SIMOX (Separation by IMplanted OXygen) Wafers.

We investigated the effectiveness of high-resistivity SIMOX (Separation by IMplanted OXygen) wafers to suppress substrate crosstalk. Small- and large-signal crosstalk measurements yielded similar results, which indicated that the frequency dependence of both types of crosstalk could be understood by analyzing the small-signal data. With the measured data, we constructed a model of substrate crosstalk with lumped elements, and found that the model described substrate crosstalk accurately. We also measured the crosstalk between actual digital and analog circuits. The measured and calculated data showed that high-resistivity SIMOX wafers could reduce substrate crosstalk by 5–10 dB in mixed-signal complementary metal-oxide-semiconductor (CMOS) circuits. Hence, we concluded that using high-resistivity SIMOX wafers was an effective way to suppress substrate crosstalk in mixed-signal CMOS circuits.

Design techniques for a 1-V operation Bluetooth RF transceiver

This paper describes circuit techniques for a 1-V operation Bluetooth PF transceiver in 0.2-/spl mu/m CMOS/SOI. Folded LC-tuned and folded transistor-current-source circuits achieve 1-V operation of the RF transceiver. Tuning circuits and a bias generation circuit for robust transceiver operation are explained.

Synchronized Multiple-Array Vibrational Device for Microelectromechanical System Electrostatic Energy Harvester

In this paper, we describe a novel structure of a vibrational micro-electro-mechanical system (MEMS) device for power generation enhancement. A synchronized multiple-array vibrational device, in which movable plates are connected by rods, increases the area of the movable plate in the energy conversion region and couples the phase of movement. The fabricated device resonates at approximately 1430 Hz with an acceleration amplitude of 6 m/s2 and nanoampere-order AC current is generated. These results confirm that this MEMS vibrational device will contribute to the progress in energy harvesting.

Design methodology of low-power CMOS RF-ICs

This paper presents design methodology for CMOS RF-ICs in the 2-GHz bond. After describing RF transceiver architectures, it introduces some low-voltage, low-power CMOS front-end circuits that use an LC-tank folding technique. Finally, it presents a 1-V, 12-mW image-rejection receiver in the 2-GHz band.

Characterization of the Interface between the Top Si and Buried Oxide in Separation by Implanted Oxygen Wafers

The electrical characteristics of the top Si-buried oxide interface in low-dose separation by implanted oxygen (SIMOX) wafers have been investigated from high-frequency and quasi-static capacitance–voltage (C–V) measurements of the buried metal oxide semiconductor (MOS) diodes proposed here. The structure of the interface has been also analyzed using cross-sectional transmission electron microscopy (XTEM). SIMOX wafers with an internal thermal oxidation (ITOX) process have a fixed charge density of 2.7×1010 cm-2 and an interface trap density of 5×109 cm-2 eV-1. XTEM analysis revealed the undulation of the interface with ITOX is about 1 lattice. From the small fixed charge density and the smooth interface, we conclude that the strain field in the top Si-buried oxide interface is small, and comparable to that of thermal oxide-Si interface. The obtained results indicate that ITOX-SIMOX wafers are useful for the fabrication of fully depleted MOSFETs.

Method for systematically designing polarization optics to maximize sensitivity of electrooptic sensors

A systematic design method is considered for maximizing the sensitivity of electrooptic sensors used for electric-field detection. The design method can be reduced to a routine procedure that includes matrix manipulation and differentiation. By applying the design method, the maximum sensitivity is realized with fewer optical components than in conventional electrooptic sensing systems. Since the proposed method shows a wide generality, it can be applied to designing sensors including various optical crystals.