摘要:

AbstractPCM is the basic coding method in speech transmission in digital telephony for the future information network system (INS). This paper evaluates the speech quality of the PCM system in a digital telephone network. A category judgement test is employed for evaluation of speech quality. This evaluation method distinguishes five grades of overall speech quality by users. First the effects of such basic PCM parameters as the number of quantizing bits, amplitude companding and input speech level on speech quality are examined. Then other factors affecting speech quality such as overall reference equivalent, circuit noise and link connection associated with introduction of PCM into the telephone network are clarified. Finally, for evaluation of the coded speech quality with consideration of network design, white noise is employed in speech envelope correlation and 8‐bit PCM system is adopted as a reference for degradatio

ISSN:8756-6621    

DOI:10.1002/ecja.4410650802

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1982

数据来源: WILEY

摘要:

AbstractThis paper describes the polarized linear predictive error coding method (POLPEC), which is a new scheme for speech recognition. Although the residual waveform power method, which is a method of speech recognition using an inverse vocal tract filter, has the advantage that the processing for recognition is simple and is suited to parallel processing, it has the drawback that it is sensitive to deviation of the input waveform to the inverse filter (i.e., the speech waveform). From such a viewpoint, this paper introduces the polarized linear predictive error coding method, which is a recognition scheme, in which it is assumed that deviation in the speech waveform is due to change in the pole of the transfer function of the filter for speech generation (called vocal tract filter) and, by improving the residual waveform power method, the sensitivity to the change of poles is decreased. The POLPEC method has the effect of decreasing the residual power by subtracting from the residual waveform sequence the component which is due to the deviation of poles. It is verified by experiment using synthetic speech that this reduces the sensitivity to the predetermined deviation of poles.

ISSN:8756-6621    

DOI:10.1002/ecja.4410650803

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1982

数据来源: WILEY

摘要:

AbstractRecent developments in memory devices have led to the proposal of a direct method of constructing combinatorial logic filter which uses bit serial operation (i.e., memory and reversible adder are used for bitwise summing of the result of weighted addition). By combinatorial construction it is possible to increase operating speed, simplify the hardware and decrease the power consumption, leading to an efficient digital filter. This paper applies bit serial operation to the canonical construction, leading to a combinatorial filter with memory capacity of 1/2N‐1. Then, bit parallel‐serial operation, which sums up the result of multibit weighted addition, is applied to the canonical construction of the second‐order section, leading to a digital filter with t/I times higher speed than in the past. It is noted that the roundoff noise in the combinatorial filter is independent of the input data, and a noise evaluation model is proposed in which the error can be independently discussed. Using the proposed model, the mean‐square error of the filter output can easily be determined. This paper deals with the drawbacks in the past theory of noise evaluation for the direct construction and performs a noise analysis for the canonical construction. The result is useful in application to LSI design for a high‐speed digit

ISSN:8756-6621    

DOI:10.1002/ecja.4410650804

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1982

数据来源: WILEY

摘要:

AbstractThe exponent function E(R), a practical measure, is used to study two kinds of decoders having 2l(l= 1, 2, …) quantization levels in a communication channel with inter‐symbol interference: a decoder which takes account of channel memory, and a decoder which does not. The values of E(R) for the same kind of decoder and an increased number of quantization levels, and for the two different kinds of decoder and the same number of quantization levels, are analytically compared for a channel with intersymbol interference of length 1. It is shown that increasing the number of quantization levels for a given type of detector, or taking account of channel memory with a given number of decoder quantization levels, can decrease the upper limit of the error probability. A comparison of channel capacities is shown to yield similar conclusions. Numerical computations indicate that when a decoder which takes account of intersymbol interference is used, the rate of improvement in the upper limit of the error probability is greater for a higher degree of intersymbol interference, but that further increases in the number of quantization levels produce almost no further improvement in such a situat

ISSN:8756-6621    

DOI:10.1002/ecja.4410650805

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1982

数据来源: WILEY

摘要:

AbstractCircularly‐polarized high gain antennas are needed for communication via broadcast or maritime satellites. With a view to developing a wideband circularly‐polarized antenna, we discuss experimental results for a structure consisting of a planar four‐terminal self‐complementary antenna on a core. The four conductors have a toothed shape which improves linear polarizability. The entire antenna structure is such that the sizes of the gaps and conductors are either equal or slightly modified. First, coupling between two opposing plates is qualitatively studied by measurement of the impedance and the radiated electric field. The self‐complementary nature of the antenna is confirmed. Next, the directivity, beam width and axial ratio of the circular polarization are studied. When the sizes of the conductors and gaps on the core are identical, the coupling between two orthogonal terminal pairs is small and the self‐complementary nature is practically preserved. This antenna has highly constant impedance and excellent directivity. The axial ratio of the antenna system, including the hybrid feed structure, is less than 0.8 dB over a larg

ISSN:8756-6621    

DOI:10.1002/ecja.4410650806

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1982

数据来源: WILEY

摘要:

AbstractTo transmit data reliably over band‐limited channels, several correlation digital transmission techniques such as continuous phase FSK, and partial response signaling have been developed. The reliability of correlative transmission systems can further be enhanced by utilizing the error correcting codes. However, it is very important to select a coding scheme that is suitable for a given transmission system. This paper proposes an encoding scheme using block code to improve the performance of certain correlative transmission systems whose transmitters' states can be represented by a simple shift register. The Viterbi algorithm is used in the decoding. The detection of symbols and the soft decision for the decoding of the proposed scheme are combined into a single process. The performance of the proposed method is demonstrated through its application to a duobinary FSK system with modulation index h = 0.5. The results indicate that the proposed scheme outperforms the MSK scheme in both the power spectral distribution and the error rat

ISSN:8756-6621    

DOI:10.1002/ecja.4410650807

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1982

数据来源: WILEY

摘要:

AbstractThere have been several attempts to expand the capabilities of loop antennas by impedance loading. In this paper, a new structure is proposed in which a reactance loads a one‐wavelength loop antenna with a reflector. It is shown that this structure is in principle suited as a circularly polarized antenna. The loading reactance is placed at 45ofrom the feed point. It is shown from numerical calculations that there exists a dimension for which a good axial ratio is obtained if the reactance is changed. Numerical results are shown for this axial ratio, input impedance, current distribution and radiative pattern at this dimension. From these results, general characteristics of this structure are found. From the model experiment, it is confirmed that circular polarization is generated from this structur

ISSN:8756-6621    

DOI:10.1002/ecja.4410650808

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1982

数据来源: WILEY

摘要:

AbstractMany millimeter‐wave applications make use of their wideband nature. Hence, it is desirable to have a broadband method for measuring fundamental quantities of millimeter‐wave circuits at many frequency points in a short period of time. This paper reports a method for wideband measurement without adjustment. It is an extension of the T‐junction method in which reflection coefficients can be measured with a simple circuit. In the T‐junction method, it is necessary to reposition the movable short at each frequency for measuring a characteristic quantity of the system. This makes wideband measurement difficult. We developed a method that enables wideband measurement by using a special T‐junction in which the width of the E‐plane of the waveguide connecting the load is narrowed. In accordance with the theoretical study, a T‐junction was designed and fabricated. The experiment at 29 ‐ 39 GHz indicated that wideband measurement is possible. The estimated error of the absolute value of the reflection coefficient of the load at 34.0 GHz is less than 0.0064 |Γ| + 0.002 for |

ISSN:8756-6621    

DOI:10.1002/ecja.4410650809

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1982

数据来源: WILEY

摘要:

AbstractAn H‐plane cosecant‐square‐beam horn antenna with a non‐planar aperture is described. A dielectric material is inserted into the horn and the aperture surface design is based on geometrical optics. The E‐plane pattern is easily controlled by changing the E‐plane aperture length. Nine antennas with various H‐ and E‐plane lengths are examined with respect to variations of several characteristics as a function of aperture length. A compact wide‐band H‐plane cosecant‐square‐beam horn with good characteristics was realized with an aperture angle of 60 degrees and an H‐plane aperture length of about 10 wavelengths. By changing the E‐plane aperture length the E‐plane pattern can be varied without degrading the cosecant characteristics in the H‐plane. In the tests the E‐plane half‐width was varied from about 44oto 72oby appropriate setting of the parameters. Hence the antenna can easily be designed in conformity with the service area and should therefore be useful for SHF broadcast and multiplex communications base stations. Further, in conjunction with an E‐plane cosecant‐beam horn antenna, both horizontal and vertical polarizations can be used in contiguous service areas to provide

ISSN:8756-6621    

DOI:10.1002/ecja.4410650810

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1982

数据来源: WILEY

摘要:

AbstractIn a 64‐Kbit dynamic MOS RAM which has a single 5‐V substrate bias voltage generator, the substrate voltage varies largely with the charge‐discharge process of the bit line as well as of the decoder circuit. Depending on the circuit design, the rate of variation can reach 90%. An example of reducing the sensitivity of a sense amplifier which utilizes a separate memory is shown. Also, in order to reduce the variation of substrate voltage, formation of a decoupling capacitor having a double‐layer polysilicon structure becomes effective. The double layer is underneath the aluminum layer on the chip. Problems associated with this structure are that, due to the alternating current of substrate voltage in dynamic operation, electrons are injected into the substrate, depending on the inversion layer of the MOS capacitor. This results in reduction of memory cell voltage “H”. Moreover, in this paper, we propose a new method of determining the electron diffusion length using the above phenomenon. Also, in order to prevent electron injection from the inversion layer, a P+layer is replaced. A desirable disturb refresh time for 64 K dynamic RAM is obtained. This RAM has a decoupling capacitance of 600 pF(27% of the total substrate capacitance). In addition to this, variation in the substrate voltage is decreased t

ISSN:8756-6621    

DOI:10.1002/ecja.4410650811

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1982

数据来源: WILEY