SOI technology has been developed for not only future ULSI, but also intelligent power ICs and sensors. In this paper the SOI fabrication process with wafer bonding and polish-stopper technologies, and its advantages for future ULSI are shown. And high crystal quality of SOI films fabricated with this method, and high speed performance of SOI devices and circuits, are shown from the data of 256 kb full CMOS SRAM chips. Moreover it is shown from the fabrication data of 4 Mb full CMOS SRAM cells that this technology has a large flexibility on device structure design. These results mean that our technology has great advantages for reduction of cell size and improvement of circuit performance.

Web APIs are offered in many Web sites for Ajax and mashup, but they have been developed independently since no reusable database component has been specifically created for Web applications. In this paper, we propose WAPDB, a distributed database management system for the rapid development of Web applications. WAPDB is designed on Atom, a set of Web API standards, and provides several of the key features required for Web applications, including efficient access control, an easy extension mechanism, and search and statistics capabilities. By introducing WAPDB, developers are freed from the need to implement these features as well as Web API processing. In addition, its design totally follows the REST architectural style, which gives uniformity and scalability to applications. We develop a proof-of-concept application with WAPDB, and find that it offers great cost effectiveness with no significant impact on performance; in our experiments, the development cost is reduced to less than half with the overhead (in use) of response times of just a few msec.

The so-called level-crossing problem of a random process is concerned with the properties of a sequence of time points at which the random process crosses with a fixed level. In order to intuitively understand the various properties of the level-crossing problem, we employ the ransom excursion model as a simple mode of a random process, by which the level dependence of the fluctuation of the number of the crossing points is derived for Gaussian processes having modified lowpass spectra. The comparison of the derived result with exact calculation is satisfactory. Secondly, we estimate how the magnitude of the fluctuation of the number for a narrow bandpass Gaussian process is different from that of an independent point process. Finally we obtain expressions for variance of the lengths of the level-crossing intervals and other quantities for a narrow bandpass Gaussian process and we succeed in interpreting the experimentally obtained behavior of the above variance.

Rate-distortion theory for the points that are distributed with the uniform density (Poisson point processes) is studied. The rate-distortion function per point for n neighboring points Rn(D) is introduced and the function R (D) is defined as a limitting function of Rn(D) for infinitely large n. A Shannon lower bound for the rate-distortion function is obtained and it is shown that the rate-distortion function for an interval length between neighboring points is the better lower bound. The behavior of Dmax(n), the value of D where Rn(D) first reaches zero, is studied. A coding scheme that constitutes an upper bound to R(D) is evaluated and it is shown that the rate-distortion function for the corresponding Wiener process is the better upper bound for large distortion. Some discussions are made on the coding theorem for our problem.

Current Web authentication frameworks have well-known weaknesses. HTTP provides an access authentication framework, but it is rarely used because it lacks presentational control. Forms and cookies, which are most commonly used, have the long-standing privacy issue raised by tracking. URI sessions, which are used in some mobile services like i-mode 1.0, disclose session identifiers unintentionally. This paper proposes iAuth, which integrates better parts of the existing frameworks and fixes their problems; iAuth allows servers to provide log-in forms, and introduces a session header to avoid servers' tracking and unintentional disclosure. Since iAuth has backward compatibility with the major legacy browsers, developers can freely introduce iAuth into their Web sites or browsers as needed. Experiments confirm its correct operation; an iAuth server is shown to support not only an iAuth client but major legacy browsers. We believe that iAuth will resolve the long-standing issues in Web authentication.

MIMO technology, which uses multiple antennas, has been introduced to the mobile terminal to increase communication capacity per unit frequency. However, MIMO suffers from the problem of mutual coupling. If MIMO antennas are closely packed, as in a small wireless terminal, a strong mutual coupling occurs. The mutual coupling degrades radiation efficiency and channel capacity. As modern terminals are likely to use three MIMO antennas, reducing the mutual coupling 3×3 MIMO is essential. Some decoupling methods for three elements have been proposed. Unfortunately, these methods demand that the elements be cross-wired, which complicates fabrication and raises the cost. In this paper, we propose a non-connected decoupling method that uses short stubs and an insertion inductor and confirms that the proposed model offers excellent decoupling and increased radiation efficiency.

This paper presents the detailed investigations on a simple multi-band method that allows inverted-F antennas (IFAs) to achieve good impedance matching in many different frequency bands. The impressive simplicity of the method arises from its sharing of a shorting strip among multiple branch elements to simultaneously generate independent resonant modes at arbitrary frequencies. Our simulation and measurement results clarify that, by adjusting the number of branch elements and their lengths, it is very easy to control both the total number of resonant modes and the position of each resonant frequency with impedance matching improved concurrently by adjusting properly the distance ds between the feeding and shorting points. The effectiveness of the multi-band method is verified in antenna miniaturization designs, not only in the case of handset antenna, but also in the design upon an infinite ground plane. Antenna performance and operation principles of proposed multi-band models in each case are analyzed and discussed in detail.

This study presents a proposal for space-saving design of built-in antennas for handset terminals based on the concept of requisite design antenna volume. By investigating the relation between antenna input characteristic and electric near-field around the antenna element and surrounding components inside the terminal, and then evaluating the requisite design antenna volume, we propose the most effective deployment for both the antenna and surrounding components. The results show that our simple proposal can help reduced, by about 17% and 31.75%, the space that the antenna element actually requires at least for stable operation inside the terminal, in the single-band designs for the cellular 2GHz band (1920-2170MHz) and 800MHz band (830-880MHz), respectively. In the dual-band design, we verify that it can reduce, the antenna space by about 35.18%, and completely cover the two above cellular bands with good antenna performance.

Waveguide characteristics of beam-expanders integrated with laser diodes were numerically analyzed by the beam propagation method (BPM) or the finite-difference time-domain (FD-TD) method. It was demonstrated that the vertically and horizontally hybrid tapered structure or an optimized refractive index in the cladding layer improve the trade-off relationship between fiber coupling efficiency and lasing characteristics. It was also demonstrated that exponentially tapering stripe width can reduce device length without sacrificing device properties.

The capacity region of a binary symmetric two-user channel is studied in the strong interference case for the transmission of separate messages. It is shown that an outer bound and a jointly achievable capacity region coincide each other for a wide range of parameter values that specify the channel and that the exact capacity region is then obtained using single-letter mutual informations.

This paper proposes a scalable multiecho cancellation system based on multiple autonomic and distributed echo canceler units. The proposed system does not have any common control section. Distributed control sections are equipped with in multiple echo cancelers operating autonomically. Necessary information is transferred from one unit to the next one. When the number of echoes to be canceled is changed, the necessary number of echo canceler units, each of which may be realized on a single chip, are simply plugged in or unplugged. The proposed system also provides fast convergence thanks to the novel coefficient location algorithm which consists of flat-delay estimation and constrained tap-position control. The input signal is evaluated at each tap to determine when to terminate flat-delay estimation. The number of exchanged taps is selected larger in flat-delay estimation than in constrained tap-position control. The convergence time with a colored-signal input is reduced by approximately 50% over STWQ, and 80% over full-tap NLMS algorithm. With a real speech input, the proposed system cancels the echo by about 20 dB. Tap-positions have been shown to be controlled correctly.

This study proposed a novel decoupling method for four planar inverted-F antennas (PIFAs) operating at 2.0GHz (f0). The edge-to-edge and center-to-center spacings of the adjacent PIFAs are extremely small (0.05λ0 and 0.17λ0, respectively), resulting in strong mutual coupling among them. In our previous study, we proposed a structure consisting of parasitic elements (PEs) and a bridge line (BL) for the decoupling of two PIFAs. One attractive feature of the proposed method is that no adjustment of the original structure and size of the PIFAs is necessary. However, as the number of PIFAs increases to four, their decoupling becomes considerably more complicated, and impedance mismatch is also an issue to be considered. Therefore, in this study, PEs and BLs are functionally developed to simultaneously achieve low mutual coupling and improved impedance matching of the four PIFAs. The simulated results showed that loading the proposed PEs and BLs onto the four PIFAs could reduce as well as maintain all mutual coupling for less than -10dB, and simultaneously improve impedance matching. Therefore, the total antenna efficiency at 2.0GHz could be significantly improved from 64.2% to 84.8% for PIFA1 and PIFA4, and from 35.9% to 74.2% for PIFA2 and PIFA3. Four PIFAs with PEs and BLs were fabricated and measured to validate the simulation results.

In this paper, a method of calculating the mean channel capacity based on S-parameter of MIMO (Multiple-Input Multiple-Output) antenna is proposed. This method exploits the correlation matrix calculated from the antenna S-parameter matrix, and offers highly accurate estimates of the mean channel capacity without dependence on SNR (Signal-to-Noise Ratio). The numerical and experimental results revealed that the proposed method can calculate the channel capacity with fair accuracy independent of the number and spacing of the antenna elements if the radiation efficiency is sufficiently high.

In this study, a novel decoupling method using parasitic elements (PEs) connected by a bridge line (BL) for two planar inverted-F antennas (PIFAs) is proposed. The proposed method is developed from a well-known decoupling method that uses a BL to directly connect antenna elements. When antenna elements are connected directly by a BL, strong mutual coupling can be reduced, but the resonant frequency shifts to a different frequency. Hence, to shift the resonant frequency toward the desired frequency, the original size of the antenna elements must be adjusted. This is disadvantageous if the method is applied in cases where the design conditions render it difficult to connect the antennas directly or adjust the original antenna size. Therefore, to easily reduce mutual coupling in such a case, a decoupling method that does not require both connecting antennas directly and adjusting the original antenna size is necessitated. This study demonstrates that using PEs connected by a BL reduces the mutual coupling from -6.6 to -14.1dB, and that the resonant frequency is maintained at the desired frequency (2.0GHz) without having to adjust the original PIFAs size. In addition, impedance matching can be adjusted to the desired frequency, resulting in an improved total antenna efficiency from 77.4% to 94.6%. This method is expected to be a simple and effective approach for reducing the mutual coupling between larger numbers of PIFA elements in the future.

In recent years, MIMO technology which uses multiple antennas has been introduced to the mobile terminal to increase communication capacity per unit frequency. However, if MIMO antennas are put closely, a strong mutual coupling occurred. Moreover, CA which uses multiple frequencies is also utilized to improve communication speed. Therefore, reducing mutual coupling in multiple frequencies is required. In this paper, we propose a dual-band decoupling method by using a short stub and a branch element and confirmed that the proposed model performed decoupling, increased radiation efficiency.