Full Papers

1. Sayaka Shiota, Kei Hashimoto, Yoshihiko Nankaku, Keiichi Tokuda, ``A Bayesian framework using multiple model structures for speech recognition'' IEICE Transactions on Information and Systems (accepted).
2. John Dines, Hui Liang, Lakshmi Saheer, Matthew Gibson, William Byrne, Keiichiro Oura, Keiichi Tokuda, Junichi Yamagishi, Simon King, Mirjam Wester, Teemu Hirsimäki, Reima Karhila, Mikko Kurimo, ``Personalising speech-to-speech translation: unsupervised cross-lingual speaker adaptation for HMM-based speech synthesis,'' Computer Speech and Language (accepted).
3. Kei Hashimoto, Junichi Yamagishi, William Byrne, Simon King, Keiichi Tokuda, ``Impacts of machine translation and speech synthesis on speech-to-speech translation,'' Speech Communication, vol.54, no.7, pp.857-866, September 2012.
4. Akira Tamamori, Yoshihiko Nankuaku, Keiichi Tokuda, ``An extension of separable lattice 2-D HMMs for rotational data variations,'' IEICE Transactions on Information and Systems, vol.E95-D, no.8, pp.2074-2083, August 2012.
5. Keiichiro Oura, Junichi Yamagishi, Mirjam Wester, Simon King, Keiichi Tokuda, ``Analysis of unsupervised cross-lingual speaker adaptation for HMM-based speech synthesis using KLD-based transform mapping,'' Speech Communication, vol.54, no.6, pp.703-714, July 2012.
6. Sayaka Shiota, Kei Hashimoto, Heiga Zen, Yoshihiko Nankaku, Akinobu Lee, Keiichi Tokuda, ``Speech recognition based on statistical models including multiple phonetic decision trees'' Acoustical Science and Technology, vol.32, no.6, pp.236-243, June 2011.
7. Kei Hashimoto, Heiga Zen, Yoshihiko Nankaku, Akinobu Lee, Keiichi Tokuda, ``Bayesian context clustering using cross validation for speech recognition'' IEICE Transactions on Information and Systems, vol.E94-D, no.3, pp.668-678, March 2011.
8. Ryuta Terashima, Heiga Zen, Yoshihiko Nankaku, Keiichi Tokuda, ``A frame-based context-dependent acoustic modeling for speech recognition,'' The transactions of the Institute of Electrical Engineers of Japan C (A publication of Electronics, Information and System Society), vol.130, no.4, pp.557-564, April 2010.
9. Heiga Zen, Yoshihiko Nankaku, Keiichi Tokuda, ``Continuous stochastic feature mapping based on trajectory HMMs,'' IEEE Transactions on Audio, Speech, and Language Processing, vol.18, no.5, pp.417-430, Feb. 2011.
10. Keiichi Tokuda, Tadashi Kitamura, ``Prediction method of speech recognition performance based on HMM-based speech synthesis technique,'' The transactions of the Institute of Electrical Engineers of Japan C (A publication of Electronics, Information and System Society), vol.130, no.4, pp.557-564, April 2010.
11. Keiichiro Oura, Heiga Zen, Yoshihiko Nankaku, Akinobu Lee, Keiichi Tokuda, ``A covariance-tying technique for HMM-based speech synthesis,'' IEICE Transactions on Information Systems, vol.E93-D, no.3, pp.595-601, March 2010.
12. Junichi Yamagishi, Bela Usabaev, Simon King, Oliver Watts, John Dines, Jilei Tian, Yong Guan, Rile Hu, Keiichiro Oura, Yi-Jian Wu, Keiichi Tokuda, Reima Karhila, Mikko Kurimo ``Thousands of Voices for HMM-Based Speech Synthesis-Analysis and Application of TTS Systems Built on Various ASR Corpora,'' IEEE Transactions on Audio, Speech, and Language Processing, vol.18, no.5, pp.984-1004, July 2010.
13. Junichi Yamagishi, Takashi Nose, Heiga Zen, Zhen-Hua Ling, Tomoki Toda, Keiichi Tokuda, Simon King, Steve Renals, ``A robust speaker-adaptive HMM-based text-to-speech synthesis,'' IEEE Transactions on Audio, Speech, and Language Processing, vol.17, no.6, August 2009.
14. Heiga Zen, Keiichi Tokuda, Alan W. Black, ``Statistical parametric speech synthesis,'' Speech Communication, vol.51, no.11, pp.1039-1154, November 2009.
15. Keiichiro Oura, Heiga Zen, Yoshihiko Nankaku, Akinobu Lee, Keiichi Tokuda, ``A Fully Consistent Hidden Semi-Markov Model-Based Speech Recognition System,'' IEICE Transactions on Information Systems, vol.E91-D, no.11, pp.2693-2700, Nov 2007.
16. Heiga Zen, Tomoki Toda, Keiichi Tokuda, ``The Nitech-NAIST HMM based speech synthesis system for the Blizzard Challenge 2006,'' IEICE Transactions on Information Systems, vol.E91-D, no.6, pp.1764-1773, June 2008.
17. Tomoki Toda, Alan W. Black, and Keiichi Tokuda, ``Statistical mapping between articulatory movements and acoustic spectrum with a Gaussian mixture model,'' Speech Communication, vol.50, no.3, pp.215-227, March 2008.
18. Tomoki Toda, Alan W. Black, and Keiichi Tokuda, ``Voice conversion based on maximum likelihood estimation of speech parameter trajectory,'' IEEE Transactions on Audio, Speech and Language Processing, vol.15, no.8, pp.2222-2235, November 2007.
19. Ranniery Maia, Heiga Zen, Keiichi Tokuda, Tadashi Kitamura, and Fernando G. V. Resende, ``An HMM-based Brazilian Portuguese speech synthesizer and its characteristics,'' Journal of Communication and Information Systems, vol.21, no.2, pp.58-71, Aug. 2006.
20. Heiga Zen, Keiichi Tokuda, Takashi Masuko, Takao Kobayashi, and Tadashi Kitamura, ``Hidden Semi-Markov Model Based Speech Synthesis System,'' IEICE Transactions on Information Systems, vol.E90-D, no.5, pp.825-834, May 2007.
21. Tomoki Toda and Keiichi Tokuda, ``Speech Parameter Generation Algorithm Considering Global Variance for HMM-Based Speech Synthesis,'' IEICE Transactions on Information Systems, vol.E90-D, no.5, pp.816-824, May 2007.
22. Heiga Zen, Tomoki Toda, Masaru Nakamura, and Keiichi Tokuda, ``Details of Nitech HMM-based speech synthesis system for the Blizzard Challenge 2005,'' IEICE Transactions on Information and Systems, vol.E90-D, no.1, pp.325-333, Jan. 2007.
23. Hisashi Kawai, Tomoki Toda, Junichi Yamagishi, Toshio Hirai, Jinfu Ni, Nobuyuki Nishizawa, Minoru Tsuzaki, and Keiichi Tokuda, ``XIMERA: a concatenative speech synthesis system with large scale corpora,'' IEICE Transactions on Information and Systems, J89-D-II, no.12, pp.2688-2698, Dec. 2006 (in Japanese).
24. Heiga Zen, Keiichi Tokuda, Tadashi Kitamura, ``Reformulating the HMM as a trajectory model by imposing explicit relationships between static and dynamic feature vector sequences,'' Computer Speech and Language, vol.21, no.1, pp.153-173, Jan. 2007.
25. Amaro Lima, Heiga Zen, Yoshihiko Nankaku, Keiichi Tokuda, Tadashi Kitamura, and Fernando G. Resende, ``Applying sparse KPCA for feature extraction in speech recognition,'' IEICE Transactions on Information Systems, vol.E88-D, no.3, pp.401-409, March 2005.
26. Hiroyuki Suzuki, Heiga Zen, Yoshihiko Nankaku, Chiyomi Miyajima, Keiichi Tokuda, and Tadashi Kitamura, ``Continuous speech recognition based on general factor dependent acoustic models,'' IEICE Transactions on Information Systems, vol.E88-D, no.3, pp.410-417, March 2005.
27. Hiroyoshi Yamamoto, Yoshihiko Nankaku, Chiyomi Miyajima, Keiichi Tokuda, and Tadashi Kitamura, ``Parameter Sharing in Mixture of Factor Analyzers for Speaker Identification,'' IEICE Transactions on Information Systems, vol.E88-D, no.3, pp.419-424, March 2005.
28. Yohei Itaya, Heiga Zen, Yoshihiko Nankaku, Chiyomi Miyajima, Keiichi Tokuda, and Tadashi Kitamura, ``Deterministic annealing EM algorithm in acoustic modeling for speaker and speech recognition,'' IEICE Transactions on Information Systems, vol.E88-D, no.3, pp.425-431, March 2005.
29. Amaro Lima, Heiga Zen, Yoshihiko Nankaku, Chiyomi Miyajima, Keiichi Tokuda, Tadashi Kitamura, ``On the use of kernel PCA for feature extraction in speech recognition,'' IEICE Transactions on Information Systems, vol.E87-D, no.12, pp.2802-2811, Dec. 2004.
30. H. Zen, K. Tokuda, T. Kitamura ''Decision tree based simultaneous clustering of phonetic contexts, dimensions, and state positions for acoustic modeling,'' IEICE Trans. Inf. & Syst., vol.87-D-II, no.8, pp.1593-1602, Aug. 2004 (in Japanese).
31. Takayoshi Yoshimura, Keiichi Tokuda, Takashi Masuko, Takao Kobayashi, Tadashi Kitamura, ``Incorporation of mixed excitation model and postfilter into HMM-based text-to-speech synthesis,'' IEICE Trans. Inf. & Syst., vol.87-D-II, no.8, pp.1565-1571, Aug. 2004. (in Japanese). Translation: Systems and Computers in Japan, John Wiley & Sons, Inc., vol.36, no.12, pp.43-50, Nov. 15, 2005.
32. Shinji Sako, Chiyomi Miyajima, Keiichi Tokuda, Tadashi Kitamura, ``A singing voice synthesis system based on hidden Markov model,'' Transactions of Information Processing Society of Japan, vol.45, no.3, pp.719-727, Mar. 2004 (in Japanese).
33. Toru Takahashi, Keiichi Tokuda, Takao Kobayashi, Tadashi Kitamura, ``Mixture density models based on mel-cepstral representation of Gaussian process,'' IEICE Trans. Fundamentals, vol.E86-A, no.8, pp.1971-1978, Aug. 2003.
34. Junichi Yamagishi, M.Tamura, T. Masuko, K.Tokuda and T.Kobayashi, ``A training method of average voice model for HMM-based speech synthesis,'' IEICE Trans. Fundamentals of Electronics, Communications and Computer Sciences, E86-A, vol.8, pp.1956-1963 August 2003.
35. Junichi Yamagishi, Masatsune Tamura, Takashi Masuko, Keiichi Tokuda, Takao Kobayashi, ``A context clustering technique for average voice models,'' IEICE Trans. Inf. & Syst., vol.E86-D, no.3, pp.534-542, Mar. 2003.
36. Yoshihiko Nankaku, Keiichi Tokuda, Tadashi Kitamura, Takao Kobayashi, ``Normalized training for HMM-based visual speech recognition,'' IEICE Trans. Inf. & Syst., vol.J86-D-II, no.2, pp.163-172, Feb. 2003 (in Japanese).
37. Takashi Masuko, Keiichi Tokuda, Takao Kobayashi, ``Very Low Bit Rate Speech Coding Based on HMM with Speaker Adaptation,'' IEICE Trans. Inf. & Syst., vol.J85-D-II, no.12, pp.1749-1759, Dec. 2002 (in Japanese).
38. Takayuki Satoh, Takashi Masuko, Takao Kobayashi, Keiichi Tokuda, ``Discrimination of synthetic speech generated by an HMM-based speech synthesis system for speaker verification,'' IPSJ Journal, vol.43, no.7, pp.2197-2204, July 2002 (in Japanese).
39. Shinichi Kawamoto, Hiroshi Shimodaira, Tsuneo Nitta, Takuya Nishimoto, Satoshi Nakamura, Kazunori Itou, Shigeo Morishima, Tatsuo Yotsukura, Akihiko Kai, Akinobu Lee, Yohichi Yamashita, Takao Kobayashi, Keiichi Tokuda, Keikichi Hirose, Nobuaki Minematsu, Atsushi Yamada, Yasuharu Den, Takenori Utsuro, Shigeki Sagayama, ``Implementation of anthropomorphic spoken dialog agent,'' Transactions of Information Processing Society of Japan, vol.43, no.7, pp.2249-2263, July 2002 (in Japanese).
40. Sinji Sako, Keiichi Tokuda, Takashi Masuko, Takao Kobayashi and Tadashi Kitamura, ``HMM-based audio-visual speech synthesis --Pixel-based approach,'' IPSJ Journal, vol.43, no.7, pp.2169-2176, July 2002 (in Japanese).
41. Mitsuru Katsumata, Hisashi Suzuki, Keiichi Tokuda, and Tadashi KITAMURA, ``A Hierarchical Algorithm for Monotonic and Continuous Two-Dimensional Dynamic Programming,'' IEICE Trans. Inf. & Syst., vol.J85-D-II, no.9, pp.1382-1391, Sep. 2002 (in Japanese).
42. Toru Takahashi, Keiichi Tokuda, Takao Kobayashi, Tadashi Kitamura, ``Vector quantization of mel-cepstrum coefficients using distortion measure for spectral analysis,'' IEICE Trans. Inf. & Syst., vol.J85-D-II, no.8, pp.1273-1283, Aug. 2002 (in Japanese).
43. Keiichi Tokuda, Takashi Masuko, Noboru Miyazaki, Takao Kobayashi, ``Multi-space probability distribution HMM (Invited paper),'' IEICE Trans. Information and Systems, vol.E85-D, no.3, pp.455-464, Mar. 2002 (translation of 55).
44. Masatsune Tamura, Takashi Masuko, Keiichi Tokuda, Takao Kobayashi, ``Speaker adaptation of pitch and spectrum for HMM-based speech synthesis,'' IEICE Trans. Inf. & Syst., vol.J85-D-II, no.4, pp.545-553, Apr. 2002 (in Japanese).
45. Kazuhito Koishida, Keiichi Tokuda, Takashi Masuko and Takao Kobayashi, ``Vector quantization of speech spectral parameters using statistics of static and dynamic features,'' IEICE Trans. Inf. & Syst., vol.E84-D, no.10, pp.1427-1434, Oct. 2001.
46. Chiyomi Miyajima, Y. Hattori, Keiichi Tokuda, Takashi Masuko, Takao Kobayashi and Tadashi Kitamura, ``Text-independent speaker identification using Gaussian Mixture models based on multi-space probability distribution,'' IEICE Trans. Inf. & Syst., vol.E84-D, no.7, pp.847-855, July 2001.
47. Chiyomi Miyajima, Hideyuki Watanabe, Keiichi Tokuda, Tadashi Kitamura, Shigeru Katagiri, ''A New Approach to Designing a Feature Extractor in Speaker Identification Based on Discriminative Feature Extraction,'' Speech Communication, vol.35, no.3-4, pp.203-218, Oct. 2001.
48. Takashi Masuko, Masatsune Tamura, Keiichi Tokuda, and Takao Kobayashi, ``Voice characteristics conversion for HMM-based speech synthesis system using MAP-VFS,'' IEICE Trans. Inf. & Syst., vol.J83-D-II, no.12. pp.2509-2516, Dec. 2000 (in Japanese).
49. Junibakti Sanubari and Keiichi Tokuda, ``RLS-type two dimensional adaptive filter with a t-distribution assumption,'' Signal Processing, vol.80, no.12, pp.2483-2495, Nov. 2000.
50. Takashi Masuko, Keiichi Tokuda, and Takao Kobayashi, ``Imposture against a speaker verification system using synthetic speech,'' IEICE Trans., vol.J83-D-II, no.11, pp.2283-2290, Nov. 2000 (in Japanese).
51. Takayoshi Yoshimura, Keiichi Tokuda, Takashi Masuko, Takao Kobayashi and Tadashi Kitamura, ``Simultaneous Modeling of Spectrum, Pitch and Duration in HMM-based Speech Synthesis,'' IEICE Trans. Inf. & Syst., vol.J83-D-II, no.11, pp.2099-2107, Nov. 2000 (in Japanese).
52. Oscar Vanegas, Keiichi Tokuda, Tadashi Kitamura, ``Lip location normalized training for visual speech recognition,'' IEICE Trans. Inf. & Syst., vol.E83-D, no.11, pp.1969-1977, Nov. 2000.
53. Junibakti Sanubari and Keiichi Tokuda, ``A new robust two dimensional spectral estimation based on an AR model excited by a t-distribution process and its QR-decomposition recursive algorithm,'' Journal of Circuits, Systems, and Computers, vol.9, nos.1-2, pp.51-66, Jan. 1999.
54. Takashi Masuko, Keiichi Tokuda, Noboru Miyazaki and Takao Kobayashi, ``Pitch pattern generation using multi-space probability distribution HMM,'' IEICE Trans., vol.J83-D-II, no.7, pp.1600-1609, July 2000 (in Japanese).
55. Keiichi Tokuda, Takashi Masuko, Noboru Miyazaki and Takao Kobayashi, ``Multi-space Probability distribution HMM,'' IEICE Trans., vol.J83-D-II, no.7, pp.1579-1589, July 2000 (in Japanese).
56. Kazuhito Koishida, Goh Hirabayashi, Keiichi Tokuda, and Takao Kobayashi, ``A 16kbit/s wideband CELP-based speech coder using mel-generalized cepstral analysis,'' IEICE Trans. Inf. & Syst., vol.E83-D, no.4, pp.876-883, Apr. 2000.
57. Takayoshi Yoshimura, Keiichi Tokuda, Takashi Masuko, Takao Kobayashi and Tadashi Kitamura, ``Speaker interpolation for HMM-based speech synthesis system,'' The Journal of the Acoustical Society of Japan (E), vol.21, no.4, pp.199-206, Apr. 2000.
58. Takeshi Wakako, Keiichi Tokuda, Takashi Masuko, Takao Kobayashi and Tadashi Kitamura, ``Speech spectral estimation based on expansion of log spectrum by arbitrary basis functions,'' IEICE Trans., vol.J82-D-II, no.12, pp.2203-2211, Dec. 1999.
59. Jun Hiroi, Keiichi Tokuda, Takashi Masuko, Takao Kobayashi and Tadashi Kitamura, ``Very low bit rate speech coding based on HMMs,'' IEICE Trans., vol.J82-D-II, no.11, pp.1857-1864, Nov. 1999.
60. Fernando G. Resende, Paulo S. R. Diniz, Keiichi Tokuda, Mineo Kaneko and Akinori Nishihara, ``New adaptive algorithms based on multi-band decomposition of the error signal,'' IEEE Trans. Circuits and Synstems II, vol.45, no.5, pp.592-599, May 1998.
61. Kazuhito Koishida, Keiichi Tokuda, Takao Kobayashi and Satoshi Imai, ``CELP speech coding based on mel-generalized cepstral analysis,'' IEICE Trans., vol.J81-A, no.2, pp.252-260, Feb. 1998 (in Japanese).
62. Kazuhito Koishida, Keiichi Tokuda, Takao Kobayashi and Satoshi Imai, ``Spectral representation of speech based on mel-generalized cepstral coefficients and its properties,'' IEICE Trans., vol.J80-A, no.11, pp.1999-2006, Nov. 1997 (in Japanese).
63. Fernando G. Resende, Paulo S. R. Diniz, Keiichi Tokuda, Mineo Kaneko and Akinori Nishihara, ``LMS-based algorithms with multi-band decomposition of the esimation error applied to system identification,'' IEICE Trans., vol.E80-A, no.8, pp.1376-1383, Aug. 1997.
64. Keiichi Tokuda, Takashi Masuko, Takao Kobayashi and Satoshi Imai, ``An algorithm for speech parameter generation from HMM using dynamic features,'' the Journal of the Acoustical Society of Japan, vol.53, no.3, pp.192-200, Mar. 1997 (in Japanese).
65. Fernando G. Resende, Keiichi Tokuda, Mineo Kaneko and Akinori Nishihara, ``Multi-band decomposition of the linear prediction error applied to adaptive AR spectral estimation,'' IEICE Trans., vol.E80-A, no.2, pp.365-376, Feb. 1997.
66. Takashi Masuko, Keiichi Tokuda, Takao Kobayashi and Satoshi Imai, ``HMM-based speech synthesis using dynamic features,'' IEICE Trans., vol.J79-D-II, no.12, pp.2184-2190, Dec. 1996 (in Japanese).
67. Fernando G. Resende, Keiichi Tokuda and Mineo Kaneko, ``Adaptive AR spectrum estimation based on wavelet decomposition of linear prediction error,'' IEICE Trans., vol.E79-A, no.5, pp.665-673, May 1996.
68. Keiichi Tokuda, Takao Kobayashi and Satoshi Imai, ``Adaptive cepstral analysis of speech,'' IEEE Trans. Speech and Audio Proces., vol.SA-3, no.6, pp.481-489, Nov. 1995.
69. Yukihiro Naito, Keiichi Tokuda and Mineo Kaneko, ``An adaptive algorithm based on non-uniform resolution filter,'' IEICE Trans., vol.J78-A, no.9, pp.1092-1102, Sep. 1995 (in Japanese). Translation: Electronics and Communications in Japan, Part 3, Scripta Technica, Inc., vol.79, no.9, pp.54-66, 1996.
70. Keiichi Tokuda, Takao Kobayashi, Toshiaki Fukada and Satoshi Imai, ``Speech coding based on adaptive mel-cepstral analysis and its evaluation,'' IEICE Trans., vol.J77-A, no.11, pp.1443-1452, Nov. 1994 (in Japanese). Translation: Electronics and Communications in Japan, Part 3, Scripta Technica, Inc., vol.78, no.6, pp.50-61, 1995.
71. Junibakti Sanubari, Keiichi Tokuda, Mahoki Onoda, ``Time series analysis based on exponential model excited by t-distribution process and its algorithm,'' IEICE Trans., vol.E76-A, no.5, pp.808-819, May 1993.
72. Junibakti Sanubari, Keiichi Tokuda, Mahoki Onoda, ``Speech analysis based on AR model driven by t-distribution process,'' IEICE Trans., vol.E75-A, no.9, pp.1159-1169, Sep. 1992.
73. Keiichi Tokuda, Takao Kobayashi, Kenji Chiba and Satoshi Imai, ``Spectral estimation of speech by mel-generalized cepstral analysis,'' IEICE Trans., vol.J75-A, no.7, pp.1124-1134, July 1992 (in Japanese). Translation: Electronics and Communications in Japan, Part 3, Scripta Technica, Inc., vol.76, no.2, pp.30-43, 1993.
74. Takao Kobayashi, Kazuyoshi Fukushi, Keiichi Tokuda and Satoshi Imai, ``2-D LMA filters --design of stable two-dimensional digital filters,'' IEICE Trans., vol.E75-A, no.2, pp.240-246, Feb. 1992.
75. Keiichi Tokuda, Takao Kobayashi, Toshiaki Fukada and Satoshi Imai, ``Adaptive mel-cepstral analysis of speech,'' IEICE Trans., vol.J74-A, no.8, pp.1249-1256, Aug. 1991 (in Japanese).
76. Keiichi Tokuda, Takao Kobayashi, Toshiaki Fukada, Hironori Saito and Satoshi Imai, ``Spectral estimation of speech based on Mel-cepstral representation,'' IEICE Trans., vol.J74-A, no.8, pp.1240-1248, Aug. 1991 (in Japanese).
77. Keiichi Tokuda, Takao Kobayashi, Soji Shiomoto and Satoshi Imai, ``Adaptive cepstral analysis --Adaptive filtering based on cepstral representation--,'' IEICE Trans., vol.J73-A, no.7, pp.1207-1215, July 1990 (in Japanese). Translation: Electronics and Communications in Japan, Part 3, Scripta Technica, Inc., vol.74, no.3, pp.36-45, 1991.
78. Keiichi Tokuda, Takao Kobayashi, Ryutaro Yamamoto and Satoshi Imai, ``Spectral estimation of speech based on generalized cepstral representation,'' IEICE Trans., vol.J72-A, no.3, pp.457-465, Mar. 1989 (in Japanese). Translation: Electronics and Communications in Japan, Part 3, Scripta Technica, Inc., vol.73, no.1, pp.72-81, 1990.
79. Keiichi Tokuda, Takao Kobayashi, Atsuhiro Tokuda and Satoshi Imai, ``Simultaneous approximation of magnitude and phase for digital filters by decomposition of maximum and minimum phase components,'' IEICE Trans., vol.J71-A, no.2, pp.260-267, Feb. 1988 (in Japanese).
80. Keiichi Tokuda, Takao Kobayashi and Satoshi Imai, ``Cepstral analysis with non-uniform spectral weighting for spectral envelope extraction,'' IEICE Trans., vol.J70-A, no.6, pp.952-959, June 1987 (in Japanese). Translation: Electronics and Communications in Japan, Part 3, Scripta Technica, Inc., vol.72, no.1, pp.20-28, 1989.