Contact us:
Prof. Dr. Haruichi KANAYA W2-456
Department of Electronics, Graduate School of Information Science and Electrical Engineering, Kyushu University. Nishi-ku Motooka 744,
Fukuoka city, Fukuoka, Japan
(Post Code: 819-0395)
E-mail: kanaya
Our Research
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Circuit design of RF-CMOS Front-End | |
| A wireless RF front-end may consist of amplifiers (LNA, PA), mixers, Voltage-controlled Oscillator (VCO) with phase-locked loop (PLL), and impedance matching circuits in between modules or at the input terminal. We are now focusing on designing all components in a single chip using novel microwave theory developed. The design of RFIC components differs from the conventional low-frequency analog circuits because conventional ones often demand high gain, low noise and low energy consumption, low loss (high Q-factor) at higher frequencies. The integration technology has recently been reduced to nanometer (nm) range and this results in significant reduction of the chip size occupied by digital and low frequency analog circuits. However, the reduction in transistor's gate width does not help in anyways, to reduce the chip size occupied by RFIC components or passive devices because spiral inductors are indispensable in the design of amplifiers, mixers, VCOs, or impedance-matching circuits. Therefore, RFIC designers and engineers have been working really hard to obtain miniaturized impedance matching circuits and microwave filters for on-chip LSI realization but the successful attempt using conventional design theory has not been reported yet. Therefore, the void in on-chip realization due to the lack of miniaturization techniques for each components using microwave circuit design rules has been observed for a long time. Here, we proposed a new design theory using Coplanar Waveguides (CPW) lines instead of spiral inductors for RFIC components such as LNA, PA, mixers, VCO and impedance-matching circuits. One of the advantages of the proposed theory is that it can save more than 50% on-chip space compared to those of the conventional theory. In addition to the state-of-the-arts technology, we utilize cutting-edge design tools, fabrication techniques and measurement equipments adhering to industry standards. We are also collaborating with industry players on SoC R&D project known as "Fukuoka Innovative Cluster Project" in finding design methodology for Low Energy and Mobile System LSIs. | |
Design of Miniaturized Filter and Matching Circuit | |
| Microwave filters such as BPF (Bandpass filter) with high frequency selectivity is another key component in wireless technology. Microwave filters are usually realized in passive structures such as microstrip or coplanar lines whose size is directly proportional to the wavelengths of interest. Low spurious responses and realization of attenuation poles near the passband to realize the sharp skirts are always sought after in microwave filter design. We fabricated those filters with improved characteristics and downsizing them using LSI technology for on-chip design. Further studies on characteristics improvement have been conducted too. On the other hand, matching circuits are necessary in RF-front end for interconnecting each components such as LNA and mixer or PA and mixer. Recently, spiral inductors have been widely used in the design of matching circuits to enhance the thermal noise performance of a wireless transceiver. Usually, it has low quality factor (Q) and may encounter self-resonance in microwave-frequency band which restricts its usage in higher frequencies, and in addition, they occupy the large on-chip space. We presents a new design theory for the impedance-matching circuits of a single-chip receiver front-end. The presented matching circuits are composed of conductor-backed coplanar waveguide (CPW) meander-line resonators, and impedance (K) inverter. The prototype front-end receiver was designed, fabricated and tested. Some advantages of the proposed method include its size is smaller than the spiral inductors and a BPF can be realized by matching circuits. | |
Design of Electrically Small Antennas | |
| Miniaturization of electronic systems has accelerated rapidly over the last few decades to meet the expectations of new generation equipment in realizing small-size components and compact systems. Antennas have not been exempted from this trend. Often, the performance of the antenna has been trade-off with its size. This has led to needlessly low radiation efficiency and reduced beamwidth. Antenna performance is fundamentally a function of size measured in wavelengths at the operating frequency. "Electrically small" antennas are radiators whose physical dimension is small compared to the resonance wavelength. In this area of research, we focus on the limitations imposed by small antenna, possible tradeoffs, recent developments, systematic design and optimization techniques. We designed and fabricated miniaturized antennas, and potential applications of these antennas could be found in RFID and wireless LAN for commercial purpose. The objective of this research is to design a highly improved radiation charateristic but very small antenna over a chip for SoC. We use Momentum, HFSS and circuit simulator driven by fast computation speed and high memory to calculate the convergence of design model. | |
Design of High-Performance Optical Switch & Router | |
| Optical Switch is the key device, which changes the route of optical signal without electro-optic conversion. In the high-speed optical communications, external optical switches using a LiNbO3 and semiconductor devices have been using. There have still been great demands for realizing higher speed and lower power optical switch for small networks, i.e. router rather than main networks. With such background, we have been studying optical switch of high speed and low-power driver circuit connected to the open-end of transmission line in order to realize the high speed. In order to obtain the high output voltage and low power dissipation, we designed the stand-by power less driver circuit by using stacked CMOS inverters. In order to transmit high-speed pulses, the gates of CMOS inverters are divided and connected with transmission line like a distributed-type amplifier. Switching speed of our proposed CMOS driver has 31.5% faster than that of a standard one. | |
Study on microwave surface impedance of HTS | |
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