Kenichiro Hosoda

Code excitation linear predictive (CELP) encoder and decoder and code excitation linear predictive coding method

There is provided a code excitation linear predictive (CELP) coding or decoding apparatus in which a code vector, which is transmitted by a codebook such as a stochastic codebook, is converted adaptively in accordance with vocal tract analysis information (LPC) so that a high quality reproduction speech is obtained at a low coding rate. Further, in order to obtain a similar effect, a pulse-like excitation codebook formed of an isolated impulse is provided in addition to the adaptive excitation codebook and stochastic excitation codebook so that either the stochastic excitation codebook or the pulse-like excitation codebook is selectively used to provide a vocal tract parameter as a linear spectrum pair parameter.

Miniaturized Microwave Filter Construction with Dielectric-Loaded Resonator and Space Coupling

A new filter construction is proposed in this paper to realize a highly miniaturized microwave band-pass filter. An element of resonator filter is composed of a square dielectric post and a round inner conductor. Each element of resonator is allocated in a housing similar to conventional combline filter, however, the length of a resonator is basically a quarter-wavelength long. The higher unloaded Q and a larger inter-resonator coupling were brought through two factors: open-boundary condition on the periphery along the dielectric post and the air spacing between resonators. Five-stages Tschebyshev response band-pass filters were developed at 800 MHz band to have 20~30 MHz pass-band and 0.8~1.0 dB insertion loss at the temperature range: -35~+80/spl deg/ C, The volume and the weight of the filters are about 25 cm/sup 3/ and 60 gramms.

Analysis and Application of a New Waveguide Structure with Dielectric Loading

A new waveguide structure has been proposed for the design of a distributed constant circuit elements at a lower microwave frequency band. Theoretical and experimental analysis of the structure has been carried out, and it was applied to the design of a compact 850 MHz band radio frequency filter. The equivalent permittivity of the waveguide (epsilon /sub eff/) is about half the perrnittivity of the medium dielectric material (epsilon /sub r/). The amount of coupling between quarter wavelength resonators (the diameter of the dielectric rod is 15 mm and epsilon /sub r/ = 20) within the cutoff waveguide (15 mm x 31 mm) is approximately 3 x 10/sup -2/ for spacing of 2 mm. Unloaded Q (Qu) of the resonator is about 1,600 using the dielectric material of which tan delta is about 1.4 x 10/sup -4/ at 6.3 GHz.

High quality variable rate video coding based on stabilization of lower frequency component

The configuration and performance of a stable, high compression video coding scheme suitable for broadcast quality are described. This scheme was developed for application to high-quality image packet transmission in asynchronous transfer mode (ATM) networks. There are two problems in implementing image packet transmission in ATM networks: the achievement of a compression scheme with high coding efficiency and the achievement of an effective compensation method for cell loss. The scheme considered resolves both these problems. It involves the division of a two-dimensional spectral image signal into several subbands, applies high-compression-ratio, motion-compensated interframe DPCM (differential pulse code modulation) and discrete cosine transform (DCT) to the high-frequency bands, and applies intraframe prediction with DCT to the baseband. This scheme also provides stable compensation for cell loss. It is shown that, based on this system, an original image signal of 165 Mb/s is compressed to about 1/15, and a high-quality reconstructed image stable to cell loss is obtained.<<ETX>>

High-performance ADPCM codec for voice and voiceband data and its application to DCME

An advanced adaptive differential pulse-code modulation (ADPCM) technique applicable to digital circuit multiplication equipment (DCME) is described. The performance of the advanced ADPCM CMOS single-chip codec regarding voice and various high-speed modems is discussed. Major issues in DCME are also addressed. The speech quality of the 32 kb/s advanced ADPCM is equivalent to that of CCITT G.721 ADPCM and also provides better quality at 24 kb/s. The 32 kb/s advanced ADPCM can transmit V.29 modem signals at 9600 b/s over two asynchronous tandem links and V.32 modem signals over four asynchronous tandem links, respectively. Evaluation results indicate that at 40 kb/s, the advanced ADPCM again provides superior performance to the 40 kb/s G. 721-based ADPCM for V.33 modem at 14.4 kb/s. It is noted that an advanced ADPCM codec having a variable rate coding capability between 24 and 32 kb/s effectively can be applied to DCME allowing a higher gain and better speech quality to be achieved.<<ETX>>

A new adaptive digital echo canceller

A composition of the newly developed adaptive digital echo canceller is proposed. This is used with hands-free phone of cellular mobile radio telephone equipment. The transfer function of the adaptive digital filter is composed of the zero-point function (FIR) and the pole function (IIR). The adaptive digital filter is adopted which is previously developed for the IIR filter and for which the sequential stability is ensured. It is confirmed by the computer simulation that the adaptive digital filter requires nearly 1/5 in the number of taps compared with that of conventional transversal filter for the same echo path model. According to the results of computer simulation, the performances of the proposed echo canceller are shown.

Analysis and Design of a New Microwave Filter Configuration with Inhomogeneous Dielectric Loading

A new configuration has been found in this paper to constract a microwave band pass filter. An element of resonator filter is composed of a square dielectric post including a round inner conductor. Each element of resonator is allocated in a housing to have the same shorted-circuited ends and the length of a resonator is a quarter-wavelength long. Total coupling is obtained enough by introduction of air gap between adjacent resonators. The coupling coefficient was obtained by the relaxation method and transmission line equation of a coupled and resonated quarter-wavelength line.