bluuebunny/crossref_metadata_2025_split huggingface dataset:
An optimum weak optical signal receiver for intensity modulation/direct detection optical communication systems
Authors: Tsukamoto Katsutoshi , Morinaga Norihiko 
Published: July 2007

AbstractThis paper presents a detailed study of a binary optical direct detection optimum receiver for the use of optical space communication systems, where a long‐distance transmission makes optical received signals extremely week. At such a low‐power operation of the receiver, the quantum discreteness structure of the shot noise process is evident in the optical detector output.A statistical model for optical detection output is derived, considering this quantum discreteness, thermal noise at the receiver circuit system, dark current at optical detector, and random photomultiplication. Moreover, the optical detection system is considered as an ideal integration system, and optical detection output is expressed by using a time‐dependent sample value vector.A logarithmic likelihood function derived from this sample value vector on the basis of maximum likelihood testing is studied, and the optimum receiver structure for weak optical signals is clarified. That is, it is shown that, even under the existence of thermal noise and random photomultiplication, primary photon count plays an essential role in signal detection similar to that in the shot noise limited case and the primary photocount estimator‐maximum likelihood detection receiver is derived theoretically. Then the error rate performance is analyzed theoretically and compared with that of a conventional direct detection receiver. As a result, it is shown that by introducing a wide‐band optical detection system, a significant improvement in error rate performance is observed over conventional receivers.
Performance analysis of the integrated train access scheme under light and medium load
Authors: Hayashida Yukuo 
Published: July 2007

AbstractThe integrated train access scheme is an access scheme integrating synchronous traffic and asynchronous traffic based on the train concept. It has a feature that an upper limit can be bounded on the train ring rotation time by limiting the number of asynchronous frames that can be connected to the train running on the ring network. Furthermore, it can also have the feature of round‐robin scheduling. An approximating analysis by a polling model is made to clarify the traffic characteristics of this integrated train access scheme under medium and light load. As a result of simulation studies, it has been found that this analysis shows a good approximation.
Design of multilayer wave absorber for oblique incidence using the point frequency matching method
Authors: Aoyagi Takahiro , Shimizu Yasutaka 
Published: July 2007

AbstractThe desirable characteristics of the wave absorber are such that it has good absorbing characteristics not only for the normal incidence but also the oblique incidence and that it has an effective absorbing capability for any polarization.In this paper, a program is developed for design of a multilayer wave absorber for the oblique incidence by means of the point frequency matching method and subsequently a design is carried out. It was successful in designing a broadband wave absorber for which the reflection coefficient is less than a certain value at frequencies above a certain design frequency once an incident angle and a polarization are specified for an obliquely incident TE or TM wave.To study both the frequency characteristics and the incident angle dependence of the designed wave absorber, contour maps were developed. By means of the contour maps, the absorbing characteristics of the wave absorber were studied. It was confirmed that good results can be obtained for oblique incidence.
Electromagnetic environmental measurement system employing frequency level selective process
Authors: Masugi Masao , Takagi Kusuo , Ideguchi Tsuyoshi , Satoh Masaji 
Published: July 2007

AbstractThis paper describes a method of measuring quasi‐stationary electromagnetic waves, whose level, generation time, radiation points, and rates of the incidents are not always constant. Those quasi‐stationary waves radiated from the amateur radio, the land mobile station, and so on, sometimes cause electromagnetic interference (EMI) and are rather difficult to detect. the frequency and the electromagnetic field level of those waves can be detected effectively by frequency domain measurements using a high‐resolution spectrum analyzer. This measurement system detects EMI waves whose peak level is above a threshold line set in the specific frequency range. Measurements were also carried out in urban areas to investigate the environment for citizen‐band. Results indicate that there is a close relationship between the occurrence rates and the human activities. This system is useful for detecting the cause of EMI and establishing countermeasures against electromagnetic waves.
Proposal of coherence multiplexed optical communication system using balanced receiver and its application for space transmission
Authors: Takeda Shinichi , Tsukamoto Katsutoshi , Morinaga Norihiko 
Published: July 2007

AbstractVarious types of theoretical studies and experimental work are being performed on coherence multiplexed systems in which multiplexing of the signal light is done by using the time incoherence of a semiconductor laser light. In this paper, the balanced receiver that uses the balanced mixer type photodetector is proposed for coherence multiplexed communication system and signal‐to‐noise power ratio (SNR) and bit‐error rate are theoretically derived. Moreover, the application of a coherence multiplexed system for space transmission is studied and the system which transmits reference light and signal light by polarization multiplexing is proposed. Moreover, the polarization diversity balanced receiver that is presented can remove the effect of polarization mismatch between the transmitter and receiver. Since both of the proposed systems are removed, then a signal‐signal beat noise (a large problem in conventional receiver using single photodetector) creates a drastic improvement in the SNR. Moreover, theoretical analysis of the receiver using an optical amplifier is performed and it is shown that there is an optimum value of spectral linewidth for obtaining the maximum SNR.
High‐density pin‐board matrix switch and its crosstalk characteristics
Authors: Inagaki Shuichiro , Kanai Tsuneo , Hosokawa Shigefumi 
Published: July 2007

AbstractThe purpose of this study is to realize the automated main distribution frame (MDF), which is indispensable in the new installation and transfer of the telephone set. the switching element, which is the key component in the matrix connection, as well as its crosstalk characteristics, are investigated. the following results are obtained: (1) systems based on various switching elements are compared, and it is shown that the pin‐board matrix is the best in the sense of the adaptability at the present stage. A detailed structure of the pin‐board matrix is proposed; (2) the effects of the shielding layer, the frequency and the defined route (insertion position of the pin) on the crosstalk characteristics of the single pinboard matrix switch is analyzed experimentally; and (3) a method is proposed and established for the probabilistic analysis of the pin‐board matrix switch with the threestage link connection.The proposed method of analysis is applied to the automated MDF. It is shown that the probability that the overall crosstalk does not satisfy the specification of the 320‐kbit/s time‐compression multiplexing transmission lines is very small (1.2 × 10‐5). In other words, it is shown that the automated MDF can accommodate the 320‐kbit/s time‐compression multiplexing transmission lines.
Fast convergence PLL synthesizer with initial phase difference
Authors: Iritani Tadamitsu , Kuge Junzo , Oie Takahiro 
Published: July 2007

AbstractA PLL synthesizer with a short frequency switching time applicable to frequency hopped spread spectrum (FH‐SS) communications is proposed in this paper. Switching output frequencies at high speed is difficult in a conventional PLL because of the low‐pass filters in the loop. In contrast to this, a sample hold‐type phase comparer that does not require a low‐pass filter is used in the proposed PLL. In addition, an output frequency is converged instantaneously by giving an initial value to the PLL during frequency switching. an initial value corresponding to each frequency can be obtained from a phase difference of the normal state of the PLL at the same frequency as that of the preceding cycle because the frequency transition of the propagation wave of FH‐SS communications is cyclical. Analysis of the errors of the proposed PLL show that the maximum error is the phase lag of VCO that occurs when an initial value is given. It is difficult to increase the hopping frequency because the switching time is shortened. While it is difficult to increase the hopping frequency since the PLL response is delayed when the PLL time constant is large, the effect of this error is slight. A method for compensating for the error due to this phase lag is proposed here. In addition, it is shown that this method allows the hopping frequency to be increased up to one‐third of the reference frequency.
A unified solution to mixed loss and delay systems with partial preemptive priority
Authors: Niu Zhisheng , Kawai Takehiro , Tadokoro Yoshiaki , Akimaru Haruo 
Published: July 2007

AbstractThis paper proposes a new priority scheme called partial preemptive priority (PPP) for mixed loss and delay system to satisfy very different individual performance requirements of loss (delay‐sensitive) traffic and delay (loss‐sensitive) traffic. the PPP scheme is a generic priority scheme which includes all the conventional priority schemes, e.g., preemptive priority (PP) and movable boundary (MB), as well as nonpriority (NP), schemes as special cases. By using the matrix‐analytic method, a unified matrix‐geometric solution to the mixed loss and delay priority systems with phase‐type Markov renewal process (PH‐MRP) inputs is derived. Numerical examples also are presented to demonstrate the effectiveness of the PPP scheme.
Multiple‐symbol differential detection for differentially encoded amplitude modulation signals and its application to 16DAPSK
Authors: Suzuki Toshinori , Mizuno Toshio 
Published: July 2007

AbstractThis paper addresses a multiple‐symbol differential detection scheme for 16 DAPSK. At the outset, conventional differential detection of 16 DAPSK is scrutinized analytically. As a result, it is seen that the energy penalty of differential amplitude detection compared with ideal coherent detection is larger than that of phase detection. Then, to improve the overall performance of 16 DAPSK, an MLSE algorithm is proposed for a large C/N as well as a suboptimum algorithm. Both allow multiple‐symbol differential amplitude and phase detection. Their performances also are evaluated through computer simulation.
Propagation characteristics of whistler‐mode signals from low‐frequency decca transmitter
Authors: Iwata Akira , Tanaka Yoshihito , Nishino Masanori 
Published: July 2007

AbstractTo resolve the propagation characteristics of low‐ frequency (LF) radio waves in the low latitude magneto sphere, the navigation radio signal (transmitting frequency of 85.725 kHz, 1.2 kW CW) from Biei Decca station in Hokkaido (geographical latitude: 43.60°N, geograph ical longitude: l42.45°E, magnetic latitude: 37.20°N) was observed at Birdsville. Australia (geographical latitude: 25.83°S, geographical longitude: 139.33°E, magnetic longitude: 37.08°S), which is the magnetic conjugate point. From the analysis of the intensity, Doppler spectrum and polarization of the magnetospheric propagation wave, the following characteristics were obtained. (1) the magnetospheric wave, which is below the detectable level during daytime, appeared around sunset and disappeared immediately after sunrise. (2) at sunset, the width of the Doppler spectrum spreading is rather narrow and the polarization is a right‐handed elliptical one. This suggests a propagation in a few ducts. (3) During the night, the width of the Doppler spectrum spreading is rather wide and the polarization is a right‐ handed elliptical one close to linear. the intensity is higher when the sustaining duration of the magneto‐ spheric propagation wave is longer. This suggests a propagation within several chamber‐type ducts, which are repeatedly generated and eliminated within a rather short period. From the calculation of the loss of the ionospher ic transmission, difference is suggested in the duct emission mechanism of the magnetospheric duct propagation at the sunset and at night.
Staggered superposed transmission of narrow band‐ limited spread spectrum multiple access signals and multicarrier high‐speed signals
Authors: Sugiyama Takatoshi , Kubota Shuji , Kazama Hiroshi , Kato Shuzo 
Published: July 2007

AbstractThis paper proposes a staggered superposed transmission scheme of narrow band limited spread spectrum multiple access (SSMA) signals and multicarrier high‐ speed signals. to lessen degradation due to mutual interference between SSMA signals and multicarrier high‐ speed signals, SSMA signals are set between two high‐ speed signal channels. Moreover, a band‐limitation filter in the transmission side and an interference‐suppression filter in the receiving side whose bandwidths are narrower than Nyquist bandwidth of spreading code chip‐rate are employed. the proposed scheme decreases SSMA signal transmission power and increases the number of SSMA channels.
Method of estimating bit‐error rate due to transverse lightning surge
Authors: Motomitsu Tamio , Yamane Hiroshi , Hattori Mitsuo 
Published: July 2007

AbstractThe longitudinal lightning surge appearing on the telecom cable between the pair of conductors and ground is changed into the transverse lightning surge between the conductors due to conversion characteristics of the system. the transverse lightning surge overlaps the signal voltage and causes bit errors. In this paper, the longitudinal and transverse lightning surges are deter mined. Using these lightning surges, a new method of estimating bit‐error rate oy simulation (numerical calculation) is proposed. Time domain and frequency domain parameters obtained by actual measurement of lightning surge are used in the simulation. Using this method, bit‐ error rate due to lightning surge can be evaluated easily. Moreover, it can cope with the changes in the telecom system and is superior to the conventional method of evaluating the bit‐error rate using actual lightning surges.
Antidisturbance characteristics in a distributed digital signal transmission system using orthogonal transform codes and recovery of signal with the estimation method
Authors: Uh Yoon , Sone Susumu , Takagi Tasuku , Kang Hyunkoo 
Published: July 2007

AbstractThe spatial distribution method using orthogonal transformation of signal is proposed and studied for its effectiveness in a new digital communication system having high immunity to impulse interferences. This method is based on the time domain consideration that spatially spread information can be recovered even if part of the information is destroyed by a pulselike disturbance. Computational investigations on the application of the distributed signal transmission method to the base‐ band digital signal transmission when discrete Fourier transform (DFT), discrete cosine transform (DCT), and Walsh‐Hadamard transform (WHT) are used as the signal distributor are covered in this research. It is also shown that the estimation of an erased symbol at the receiver is possible using an estimation method.
Spectral domain analysis of a proximity feed polarimetric microstrip antenna
Authors: Miyazaki Toshiyuki , Itoh Kiyohiko 
Published: July 2007

AbstractAs a form of feeding the microstrip antenna, there is a method of exciting the patch via a gap from the semiinfinite feed line. In this scheme, the polarization plane can be switched by changing the stub length. Due to the effect of the feed line on the input and polarization characteristics and to the expected strong coupling by the surface wave through the gap, the rigorous analysis by the conventional method has not been possible.In this paper, the operating principle of the present model is presented. In addition, a model of the current basis on the feed line is proposed including the scattering by the patch. Further, by means of the spectral domain method, the input and polarization characteristics are analyzed rigorously. the behavior of the polarization is shown analytically when the frequency and the stub length are varied.
Micro mass axis alignment device with piezoelements for optical fiber and its application to optical connection
Authors: Aoshima Shin‐Ichi , Kubota Manabu , Yabuta Tetsuro 
Published: July 2007

AbstractFusion mass‐splice devices for optical fibers have been developed for splicing fiber ribbons. However, these devices use only V‐grooves to align the optical fiber axes. Thus, axis misalignment errors easily occur due to the following reasons: (1) accurate design of a V‐groove is difficult; and (2) optical fibers have core eccentricity. These both cause an increase in splice loss.We first proposed here some types of axis alignment device that can independently align individual optical fibers. Next, axis alignment experiments were performed with the designed device. Experimental results indicated that it will be possible to align a fiber core axis of 0.1‐μm order precision by using feedback control. The axis alignment range is approximately 20 × 20 μm. The proposed axis alignment device was applied to the fusion mass‐splice device by a researcher from another company. Average splice loss was 0.05 dB for four fiber ribbons of 1.55‐μm DSF. These results show that the proposed device has enough performance for the fusion mass‐splice device. Finally, we proposed a device for low‐loss optical coupling between an optical waveguide plate and optical fibers.
Estimations and evaluations of radiation patterns of personal handy phone systems by numerical electromagnetics code‐2 (NEC2)
Authors: Saitoh Hirotaka , Omiya Manabu , Itoh Kiyohiko 
Published: July 2007

AbstractTo verify that the electromagnetic analysis system NEC2 is effective for the development and design of the second generation digital cordless telephone investigated for use in the frequency band of 1.9 GHz. Two types of personal handy phone models with metal housing and plastic housing were fabricated and measurement and analysis by NEC2 were carried out for radiation patterns. The analysis results were found to agree with the measured results in regard to the absolute gain and shape. For the metal housing model, examples of the procedures were presented for modeling the housing by wire grids or surface patch elements. It was shown that the analysis results agree well with the measured results. It was also found that the radiation pattern of the plastic housing model is only slightly affected by the housing material. By realizing the installed circuit as an analytical model, estimations and evaluations of the radiation pattern are possible by means of NEC2. As a result, NEC2 is effective for the analysis of the radiation pattern of personal handy phone systems at 1.9 GHz.
Characteristics of whistler wave normal distributions at the exit of low‐latitude duct
Authors: Nakamura Yoshikatsu 
Published: July 2007

AbstractAccording to the direction‐finding observation of whistler at low latitudes, the whistlers come from a narrow region of the zenith and exhibit morphology at ionospheric exits. When ionospheric transmission characteristics of the very low‐frequency (VLF) radio wave emitted to the ground from the magnetic field‐aligned duct due to the irregularity of the ionosphere are computed, or when the results of the VLF direction‐finding observation on the ground are discussed, distribution of the wave normal of the radio wave at the duct exits is important.Here, the wave‐normal distribution of the VLF whistlers at the duct exit, namely the wave normal of the VLF whistlers at each part of the duct exit, is computed by means of the two‐dimensional ray tracing based on the duct propagation model assuming low latitudes. It was found that there are two kinds of wave‐normal distributions, i.e., upward and downward. The cause of the generation of the two kinds of distributions was clarified qualitatively by the duct‐propagation theory. Also, the factors for various characteristics of the wave‐normal distributions at the duct exit were investigated. Especially, for the downward wave‐normal distributions, there is a region at the center of the duct where the wave normals are directed vertically downward due to the effect of the vertical gradient of the ionosphere applied in the duct. This region contributes to the transmission of the whistler to the ground.
Rectangular loop antenna for circular polarization
Authors: Murakami Yuichi , Yoshida Akimasa , Ieda Kiyokazu , Nakamura Takashi 
Published: July 2007

AbstractIt is shown here that a rectangular unloaded one wavelength loop antenna works as a circularly polarized antenna. Its operating principle is presented. The current distribution on the loop of this antenna can be controlled by the ratio of the major and minor sides. It is a single‐feed antenna with the simplest configuration. The current distribution of this antenna can be decomposed to the traveling wave mode currents for the forward and backward waves. Based on this fact, the condition for the circular polarization is derived in terms of the current value at the center of each side of the loop and the effective length. Based on the investigation of the realization method for this condition, a circularly polarized antenna off‐center‐fed at a corner of the loop was actually designed and the various characteristics, such as axial ratio and the directivity, were derived. From this study, it is found that a good circular polarization can be obtained with the antenna height within a range near 0.13λ from the reflector. Validity of the theoretical results is confirmed by experiment.
Tri‐reflector antennas eliminating cross‐polarized component based on beam‐mode analysis
Authors: Furuno Takayoshi , Urasaki Shuji , Katagi Takashi 
Published: July 2007

AbstractThe offset‐type antennas have efficient and desirable wide‐angle radiating characteristics in comparison to the rotationally symmetric parabola antennas and Case‐grain antennas because there is no blocking due to the primary radiator, subreflector, and supporting members. However, in the microwave relay link, the two orthogonal polarizations are used so that the cross‐polarized component generated by the asymmetric reflector is a problem.To resolve this problem, the tri‐reflector offset antenna is used which is constructed such that the cross‐polarized component generated by the main and subre‐flectors are cancelled in the geometrical optics manner. When such an antenna is used at low frequencies, the electromagnetic field distributions are different from those conceived by the geometrical optics so that the cross‐polarized component cannot be eliminated completely. To improve this discrepancy, the beam‐mode expansion method has been used for optimization of the cross‐polarization characteristic by successive calculations. Since this method takes into account the phase, improvement is better than the geometrical optics. However, the method is not convenient for perspective for optimization and is difficult in completely eliminating the cross polarization.In this paper, the cross‐polarization elimination condition is derived by taking into account the phase of the cross‐polarized component generated by the reflector. The shape of the reflector system satisfying this condition is presented and the design method is described. Further, it is shown that the derived condition is a geometrical relationship not related to the frequency.