Electronics and Communications in Japan Part I-communications 

About: Electronics and Communications in Japan Part I-communications is an academic journal. The journal publishes majorly in the area(s): Antenna (radio) & Antenna measurement. Over the lifetime, 3063 publications have been published receiving 10818 citations.

An adaptive filtering algorithm using an orthogonal projection to an affine subspace and its properties

Abstract: The LMS algorithm and learning identification, which presently are typical adaptive algorithms, have a problem in that the speed of convergence may decrease greatly depending on the property of the input signal. To avoid this problem, this paper presents a geometrical discussion as to the origin of that defect, and proposes a new adaptive algorithm based on the result of the investigation. Comparing the convergence speeds of the proposed algorithm and the learning identification by numerical experiment by computer, great improvement was verified. The algorithm is extended to a group of algorithms which includes the original algorithm and the learning identification, which are called APA (affine projection algorithm). It is shown that APA has some desirable properties, such as, the coefficient vector approaches the true value monotonically and the convergence speed is independent of the amplitude of the input signal. Clear conclusions are also obtained for the problem as to what noise is included in the output signal when an external disturbance is impressed or the degree of the adaptive filter is not sufficient.

A proposal on digital watermark in document image communication and its application to realizing a signature

Abstract: With the advance of telematic technology, increasing document image information utilized in the state of soft copy is expected. In these situations, copies of obtained document image information are made illegally with ease, and hence the validity authentication of the information itself and its provider becomes more necessary. Since document image information to be authenticated exists in a form which can be read at an unidentified number of receiver terminals, the realization of an authentication scheme where document image and signature are combined is necessary. This is characteristic of document image information including nature pictures and photographs. This paper proposes a new concept of signature, which is called “digital watermark” for document image communication. A digital watermark is the coding scheme in which secret information is embedded into a document image similar to a watermark. Image coding schemes already proposed are available to realize a digital watermark. We present a method of obtaining a digital watermark using a well-known predictive coding algorithm. Also, we define a criterion for security and show to what extent the digital signature is safe using simulation results, where two or three illegal actions are considered.

Development and characteristics of a biological tissue-equivalent phantom for microwaves

Abstract: Various phantoms (simulated biological bodies) have been proposed as a biological model for studies of electromagnetic effects on the human body. This paper reports the characteristics of the phantom developed by the authors that realized electrical characteristics equivalent to the biological body. Examples of its communication and clinical applications are presented. The present phantom is made of agar, polyethylene powder, sodium chloride, TX-151, preservative, and deionized water and simulates the relative permittivity and conductivity of a high-water-content tissue. In the present phantom, electrical characteristics almost equal to those in the biological tissue are realized with a single composition ratio over the frequency range of 300 MHz to 2.5 GHz. It is also possible to simulate the electrical characteristics of an arbitrary high-water-content tissue by adjustment of the composition. No special equipment is needed for fabrication and the preservation is easy. Further, as examples of applications of this phantom to the human body, the SAR measurement examples are presented in the COST 244 human head model and coaxial-slot antenna for hyperthermia. The present phantom is useful as a human model to study the mutual effects of the human body and electromagnetic waves. © 2000 Scripta Technica, Electron Comm Jpn Pt 1, 84(4): 67–77, 2001

Mel Log Spectrum Approximation (MLSA) filter for speech synthesis

Abstract: The spectral envelope of speech can be represented efficiently by the log magnitude spectrum on the nonlinear frequency scale, which is close to mel scale (called mel-log spectrum). the mel cepstrum defined by its Fourier coefficients is also considered to have a suitable property as the parameter to represent the spectral envelope. So far, no satisfactory filter has been reported for the synthesis approximating the mel-log spectrum. This paper presents a method of constructing the mel-log spectrum approximation (MLSA) filter, which has a relatively simple structure and a low coefficient sensitivity, together with a design example of MLSA filter for speech synthesis. the transfer function of MLSA filter is represented by Pade approximation, which approximates the exponential of the transfer function of the filter (so-called basic filter). Since the transfer function of the basic filter is represented by a polynomial with the transfer function of the first-order all-pass filter as the variable, it is necessary in the realization of the filter to delete from the feedback loop the path without a delay. By the construction method of MLSA filter shown in this paper, the path without delay can easily be deleted from the feedback loop in the MLSA filter. the obtained MLSA filter is of relatively simple structure and has low coefficient sensitivity. the quantization characteristics of the coefficient are also satisfactory.

A construction of vector quantizers for noisy channels

Abstract: Recently, vector quantization has become noted as a highly efficient coding method of image and voice data. So far, many of the highly efficient coding problems, or service coding problems, have been studied separately from channel coding problems. This paper reconsiders vector quantization jointly optimizing source coding and channel coding, and proposes a new vector quantizer for noisy channels. Vector quantizers for binary symmetric channels are designed for memoryless Gaussian source, Gauss-Markov source and the real images, and are compared with the conventional vector quantizer which does not take account of channel errors. As a result, it is shown that the performance of the proposed vector quantizer is improved without adding the redundancy for error correction, and the improvement of the performance of the proposed vector quantizer for noisy channels over the conventional vector quantizer becomes significant for highly correlated sources and longer block length.