bluuebunny/crossref_metadata_2025 huggingface dataset:
A rocket‐borne antenna consisting of a monopole and a major angle corner reflector
Authors: Kamata Yukio , Ichikawa Mituru , Hayashi Tomonao
Published: July 2007

The radiation pattern of a major angle corner reflector in the magnetic plane is close to uniform in a broad range (broad radiation pattern) and a reasonable front‐to‐back ratio can be obtained. Since the configuration also is simple, it is considered useful as a rocket‐borne antenna. This paper describes the development of the antenna based on a dipole with a major angle corner reflector as an S band (2290 MHz) rocket‐borne antenna. To satisfy the conditions (small, lightweight, mechanically strong and thermal resistant) for a rocket‐borne antenna, the antenna element is made of a monopole buried in teflon (with a relative permittivity of ϵr = 2) so that the structure is small.

The radiation characteristics with respect to various parameters are computed numerically for a basic major angle corner reflector antenna. Based on this result, the radiation characteristics with respect to the aperture angle of the experimental model antenna are derived. From these results and the conditions for the rocket‐borne antenna, an optimum design is carried out. From the experiment, it is confirmed that the present antenna has an extremely broad radiation pattern and a superior radiation characteristic to the back side of the rocket.
Design and electrical characteristic evaluation for interface circuit in isdn bus wiring system
Authors: Nakano Shizuo , Nagai Naofumi
Published: July 2007

ISDN basic access interface provides transmission capability of two B channels and one D channel for various telecommunications services. The electrical characteristics of this interface are strictly regulated in CCITT recommendation I.430 to allow up to eight terminals to be connected in a bus wiring system. This paper describes a design method for achieving desired line interface characteristics, including output voltage with specified loads, transmitter output impedance at inactive state, receiver threshold voltage and cut‐off frequency of a low‐pass filter. The electrical characteristics of the line interface circuit based on the proposed design are measured by using practical bus wiring systems and are confirmed to satisfy recommendation I.430.
An adaptive phase‐control digital pll
Authors: Kubo Hiroshi , Iizuka Ikuo
Published: July 2007

With the recent development of digital LSI integration, numerous studies have been made on the digital implementation of the phase‐locked loop (PLL). Among those, the binary quantized digital PLL, which is simple in circuit structure and the multilevel quantized digital PLL which is an extension of the forementioned type are considered interesting.

This paper proposes a new type of sequential loop filter (SLF) for the multilevel quantized digital PLL by which the tracking range can be expanded. As in the case of the random‐walk filter, the general idea about SLF has been to control the output phase by smoothing the result of phase comparison. Consequently, when the input frequency of the phase information, mark ratio is low, it has been difficult to keep a wide tracking range for any extent of the frequency offset.

In the proposed SLF(APCF) (adaptive phase‐control fitler), in contrast to the smoothing process, an adaptive search of the phase‐control interval is made by applying the steepest descent method to the result of phase comparison. In this paper, the algorithm of APCF is described first and the evaluative expressions of the performance are derived theoretically.

Some evaluations are given to compare adaptive phase‐control filter with the conventional sequential loop filter by simulation. It is shown that the output jitter for the low mark‐ratio is small and the degradations such as the reduction of the tracking range are small even if the mark‐ratio is decreasing.
Optimum adaptive equalization of selective fading channel based on time‐varying channel model
Authors: Munemura Koichi , Ogiwara Haruo
Published: July 2007

The time‐varying transmission characteristics, as in the case of the selective fading channel, are modeled. Based on the model, the optimum adaptive equalization is proposed considering the speed of variation. Proposals have already been made on this problem for the case of the baseband transmission.

This paper extends the results to the case of band transmission and discusses several points which have not been covered in previous studies. First, the model is extended to the case where the overall system including the channel is the band transmission, and the adaptive equalization algorithm is derived using the complex Kalman filter. A simulation based on the model is executed.

The tolerable range is determined for the frequency deviation between the carrier and the local oscillation considered as a cause of the deterioration of the performance, along with the variation of the transmission characteristics. To suppress the effect of the decision error in the decision feedback equalization, the training procedure periodically is combined and the effect of the method is analyzed.

Finally, the effect of the deviation between the model parameter of the channel characteristics and the equalizer is examined, the tolerable range is determined, and the usefulness of the algorithm is demonstrated.
Congestion control for bursty video traffic in ATM networks
Authors: Kubota Kouji , Murata Masayuki , Miyahara Hideo , Oie Yuji
Published: July 2007

In an ATM network, congestion controls as well as traffic controls, e.g., call admission control and policing control, are important to efficiently transmit multimedia traffic while satisfying their different required grade‐of‐services.

This paper analyzes a congestion control scheme required for ATM networks. With the control scheme, when the buffer queue length in an ATM switch exceeds a certain threshold, congestion control is applied and. cells from lower priority traffic such as voice are rejected. As a result, higher‐priority traffic such as compressed video can be transferred with good quality.

Cell loss probabilities are analyzed for each multimedia traffic at a switching machine buffer and the effectiveness of the congestion control is studied. By numerical examples it is shown that the threshold value to apply the congestion control is an important parameter for effectively transferring multimedia traffic.
Passive reflector to reduce fading due to angle‐of‐arrival variation on microwave links
Authors: Komai Tomohiro
Published: July 2007

A passive reflector is used as a simple repeater system to connect transmission and reception points with no direct line of sight. When the wavelength is short and the reflector has a large structure, the radiation characteristics of the reflector exhibit sharp variations. A phenomenon such as fading is introduced when the direction of the wave incident on the reflector is bent due to a change of the atmospheric refractive index or the angle of arrival varies due to the vibration of reflector by wind pressure.

This paper proposes a reflector structure which is made from element reflectors whose positions are displaced slightly and the depth of nulls in the radiation pattern appearing in horizontal and vertical planes can be reduced. Moreover, the radiation pattern of the proposed structure and its relationship with the position of element reflectors and the reflector gain are clarified. The experiments were performed at the reflector repeater stations where the received electric field fluctuations occurred quite frequently and the wave bending was confirmed by the measured field fluctuations. Moreover, by making the reflector structure as proposed here, the field fluctuation width may be suppressed and the validity of this method is demonstrated.
Recent spreading codes for spread spectrum communication systems
Authors: Tachikawa Shin‐Ichi
Published: July 2007

This paper presents recent spreading codes and their applications to spread spectrum (SS) systems.

First, co‐channel interference in spread spectrum multiple access communication systems (SSMA) and cross‐correlation functions are described, and the relationship between new “No sequences” with low cross‐correlations and other well known sequences is summarized.

Second, an SSMA using very low‐rate convolutional codes proposed by Viterbi is described. With this SSMA the spectral efficiency can be improved over that of FDMA using a guardband.

Finally, optical orthogonal codes for fiber networks, orthogonal Gold sequences, orthogonal Bent sequences for synchronous SSMA, majority logic combination sequences using M‐sequences, and generalized Geffe sequences for rapid acquisition are described.
A digital multisignature method for facsimile‐mail service
Authors: Tanaka Kiyoshi , Nakamura Yasuhiro , Matsui Kineo
Published: July 2007

In the wake of the development of computer‐aided facsimile equipment, office documents may be digitized, circulated on a network, and in the near future stored into files as soft copy. In this paper, we call this type of service facsimile‐mail, and we discuss a multisignature method which is applied to facsimile documents. This method makes it possible to sign digital documents multi‐plexively and simplify the document exchange process. Document management is simplified and the reliability of the network is improved.
A code division multiplex using manchester‐coded orthogonal sequences
Authors: Habuchi Hiromasa , Hasegawa Takaaki , Hakura Yukio , Haneishi Misao
Published: July 2007

There has been increasing interest recently in code division multiplex (CDM) systems. The authors reported a CDM system using pseudo‐orthogonal Manchester‐coded M‐sequence pairs. For this CDM system, the effective energy per bit in the received signals is reduced (M + 1)/2M times as much as the transmitted energy per bit. Moreover, the bit error rate (BER) of the 3M‐plex system, which uses the “a‐chip‐shift” multiplex operation alone, does not converge on zero even if Eb/N0 increases.

This paper proposes a CDM system using Manchester‐coded orthogonal sequences which consists of an M‐sequence M chip and an additional chip. The proposed 3M‐plex system is a combination of the “a‐chip‐shift” multiplex operation and the amplitude multiplex operation. The proposed systems do not have loss of the effective received signal energy. The BER of the proposed systems converges to zero with increasing Eb/N0. Moreover, the proposed system out performs the Manchester‐coded multilevel transmission system.
A study of the distortion and propagation time‐delay of Loran‐C pulse wave based on a model of the propagation path
Authors: Kouguchi Nobuyoshi , Sato Masashi , Morinaga Norihiko
Published: July 2007

The main cause of the absolute positioning error in the Loran‐C system is in the occurrence of the propagation time delay error caused by the fact that the propagation speed of the pulse signal on the actual propagation path is different from that assumed in the formation of the Loran‐C maritime chart. The propagation path characteristics not only cause the propagation time delay of each received pulse signal but also generates waveform distortion in the received pulse. Hence, it is possible to estimate the propagation delay time by means of this waveform distortion.

At present, a measure of the distortion of the pulse waveform distortion of the Loran‐C is envelope to cycle difference (ECD). In this paper, as a new measure for the pulse‐wave distortion to estimate the propagation time delay, CHACLE, or change of half‐cycle length, is proposed.

A method for correction of the absolute positioning error is provided based on the estimation of the propagation time delay from the measures of the wave‐form distortion (CHACLE and ECD) by means of the simplified propagation path for an easy analysis and of the general propagation path. It is demonstrated that CHACLE is superior to ECD in terms of the effect of correction. Further, to confirm the validity of the correction method proposed in this paper, the present method is applied to a propagation path model resembling the mixed propagation path used in the United States to estimate the pulse time delay. It is confirmed that the absolute positioning error can be reduced to less than about 20 percent.
Wideband hybrid diplexer using ridged waveguides
Authors: Ishida Osami , Miyazaki Moriyasu , Isota Yoji
Published: July 2007

To develop a broadband diplexer to be used for the Ku band satellite communication earth station, a hybrid diplexer is proposed based on the branch waveguide directional coupler in which the main and auxiliary waveguides are ridged waveguides. The theoretical discussions and experimental results are described.

First, the characteristics of the hybrid diplexer and those of the constituent components are expressed in terms of the scattering matrix so that the effect of the hybrid coupler is presented. Next, the characteristics of the branch waveguide directional coupler used as a hybrid coupler are studied theoretically. It is pointed out a broadband operation is possible by the use of ridged waveguides for the main and auxiliary waveguides. Further, using the transmit and receive diplexer for the Ku band satellite communication earth station as an example, the design and fabrication have been carried out to demonstrate the validity of the theoretical results.
A characteristic of primary distributed‐type switching network
Authors: Takase Juhro
Published: July 2007

This paper considers the primary distributed‐type switching network which serves as the prototype for the distributed switching network. A method is shown to determine the route with the minimum number of tandem stages from the originator to the destination nodes in the network (called shortest route). The shortest route is given either by the straight path directly connecting the originator and the destination switching nodes, or, if such does not exist, by the following path.

Consider the parallelogram that directly connects the originator and the destination switching nodes. Then the route is obtained from the originator switching node to the destination switching node by connecting arbitrarily the unit links on the border and the inside of the parallelogram, in the same direction as that of the edges of the parallelogram from the originator switching node to the destination switching node. The number of shortest routes between the originator and the destination switching nodes increases following the exponential function of the distance between the originator and the destination switching nodes. The number of tandem stages in the shortest route increases linearly with the distance. If a honeycomb‐type network is employed, the number of tandem stages in the shortest route can be reduced by approximately 15 percent at the maximum, compared to the grid‐type network. When a failure such as blocking is produced between the originator and the destination, there exist three kinds of shortest routes depending on the point of generation.
Fundamental study on optical fiber direct transfer splicing
Authors: Kobayashi Hideo , Ueno Kouji , Watanabe Ichirou , Uenoya Takuya
Published: July 2007

With regard to the direct transfer splicing of optical fibers in which the fibers are cut, moved, and spliced to other fibers at arbitrary locations along the line, the results of basic investigations on fiber vibrations when the fibers are cut and moved are presented. The solution method of the fiber longitudinal and lateral vibrations due to the tensile force and bending moment exerted when it is cut is indicated. The relation among fiber length, tensile force, settling time of vibrations, and loss variations are clarified.

With regard to the behavior of fiber movement, the solution method of the lateral vibrations when one terminal is fixed also is presented and the relation among movement speed, fiber length, and settling time is determined. From these investigations, the requirements under which the loss variations associated with fiber cutting and its movements can be kept below 1 dB are clarified.
Design of a PSK modulation/demodulation method free from interruptions
Authors: Yamazaki Masami , Tomoda Yusuke , Takahata Fumio
Published: July 2007

This paper discusses a PSK modulation/demodulation method free from interruptions providing continuous telecommunication services. The feature of the system is that the transmission rate or the carrier frequency is switchable without interruptions during communications. Functions of the system are outlined. The design procedure and design results are presented.

Another feature of the proposed method is its transmission format. In the normal operation, a control information is inserted into the transmission format and a preamble is inserted only when the transmission rate or the carrier frequency is to be changed. By this elaboration, interruptions can be avoided.

As a detailed example of the design, a link configuration is assumed where the convolution encoding Viterbi decoding with coding rate of one‐half is used as the forward error correction scheme, and the information rate is made variable among 2B + D, B + D, and D based on the basic ISDN service. Parameters concerning the transmission format and the modulation/demodulation are determined. The control information and protocol required in the functional switching needed in avoiding interruptions are also discussed. By this method, limited radio frequency resources can efficiently be utilized, appropriately varying the transmission rate according to traffic or switching the carrier frequency.
Digital cross‐connect system control algorithm for reducing rearrangement needs
Authors: Fujii Nobuo
Published: July 2007

The digital cross‐connect system (DCS) employs cross‐connect equipment composing the synchronized digital network. The scale of DCS is enlarged using the rearranged‐type TST switches based on the nondisturbing rearrangement control algorithm.

This paper considers the case where DCS is controlled using the proposed rearrangement pattern search algorithm. A control algorithm is proposed which can avoid the generation of a blocking state, thereby necessitating the rearrangement control, and can realize the nondisturbing rearrangement control when a blocking is produced. The effectiveness of the method is demonstrated by computer simulation.

In this paper, knowledge in other studies such as the mechanism of block generation is summarized. Then an evaluation measure is introduced for the S switch state. A control algorithm is proposed which suppresses the generation of the blocking by selecting the S switch timeslot to maximize the evaluation measure. It was verified by the computer simulation that the generation of the rearrangement control is reduced by approximately 5 to 30 percent, depending on the switch structure, compared to the algorithm that minimizes the evaluation measure for the switch. A nondisturbing control method for the switch also is presented.
An intelligent network call model incorporating broadband isdn controls
Authors: Wakamoto Masaaki , Fukazawa Mitsunori , Kim Moo Wan , Hattori Shinmi
Published: July 2007

Intensive research and development efforts have been made on the intelligent network (IN) to realize diversified and advanced telecommunication services and the early introduction of new services under a multi‐vendor environment.

Earlier research and development, however, assume the conventional telephone service and narrowband ISDN services and gave little consideration to the broadband ISDN.

The study of the IN from the viewpoint of the broadband ISDN is urgent considering the systematic realization of the services (i.e., multimedia services) that are not yet sufficient as well as the increase of the demand for the development of new services.

This paper proposes the call model, which provides the basis for realizing the IN architecture incorporating the broadband ISDN. First, the basic concepts are defined clearly. Then the call model is proposed which can realize the general connection control for various connection types as well as the flexible control for the multiple virtual channels in the multimedia environment. The model also facilitates the control of the interactions among related services. Finally, the service control characteristics of the proposed call model are investigated.
Distribution of positioning error in a global positioning system
Authors: Okuda Kuniharu , Yasuda Akio
Published: July 2007

The distribution of the positioning error in a global positioning system (GPS) depends on the allocation of satellites. Thus, the agreement between the covariance ellipse derived from the allocation of satellites and that derived from the positioning error distribution of the actually measured data is examined for two reception systems, i.e., the sequential and the parallel processing systems. The result shows that the two covariance ellipses agree well, although the situation depends a little on the shape of the ellipse as well as the azimuth and elevation of the satellite.

The size of the ellipse is approximately one‐half in the parallel processing system compared to that of the sequential one. It is proved by the results of the analysis that the distribution of the error is anticipated before the measurement or the positioning during navigation and is represented by an ellipse. The method is applied to a navigating ship. It is shown that the display of the error distribution together with the positioned point is useful to the navigator in determining the steering of the ship in the sense that the reliability for the position of the ship is increased.
Bit error rate and power penalty of optical dpsk communication systems with echo
Authors: Yamaguchi Yoshiaki , Takeda Shinichi , Hiranos Nobuo
Published: July 2007

It is known that the bit error rate is deteriorated if there exist echoes on the transmission line. This paper presents a theoretical analysis on influences of an echo on the bit error rate in the optical DPSK communication system. In general, there exists a floor in the bit error rate due to the phase fluctuation of the laser light, which is not reduced by increasing the received optical power. It is shown that the floor value increases with the increase of the amplitude ratio of the echo to the principal wave, as well as the increase of the delay time. It also is shown that the effect of the echo is more remarkable when the bit rate is higher and the spectral linewidth of the laser light is narrower.

Finally, the bit error rate is calculated as a function of the received optical power and the power penalty is evaluated. The relation between the bit error rate for which the effect of the echo cannot be ignored and the spectral linewidth is discussed. The features of this paper are that the echo with a small delay time, which has some correlation to the principal wave, can be analyzed.
Design of an all‐digital multilevel modulator and its application to variable‐capacity transmission
Authors: Okada Takashi , Aikawa Satoru
Published: July 2007

With the advent of the radio relay system and multilevel modulation, the multicarrier system and variable capacity transmission system are proposed to realize excellent performance in the fading channel. Accordingly, it is desired to realize a highly functioned MODEM which can cope with those systems in a flexible way.

On the other hand, intensive studies have been made on digital signal processing in the modulation and demodulation in the field of data modem. However, these methods consider the low‐rate system of less than 100 Kbaud and are difficult to apply directly to the system where the transmission rate of 10 Mbaud or above is required.

For the foregoing reasons, this paper considers the realization of the all‐digital modulator which can realize the high‐capacity transmission of over 10 Mbaud for the multilevel modulation system, such as 256 QAM.

This paper discusses the design of the digital filter with excellent intersymbol interference. The condition for the carrier frequency for a given clock rate is presented. Then a variable multilevel modulator with a simple correction circuit is proposed which can be applied to the variable‐capacity transmission system.

Finally, the proposed circuit is constructed and it is confirmed that an excellent modulation performance is obtained without adjustment in various multilevel modulation systems.
Mac reconfiguration mechanism for a dual‐ring lan
Authors: Nakayashiki Susumu , Kashios Jiro , Harakawa Takeshi
Published: July 2007

In a reconfiguration mechanism for improving the RAS of a ring LAN, it is necessary to guarantee the proper functioning of communication functions up to the medium access control (MAC) layer. This paper proposes a reconfiguration mechanism for distributed‐control dual ring LANs which maximizes the size of the ring while maintaining MAC layer communication functions by automatic ring merging and wrapback. Each station bases its actions on the state of the two input links. When a link fails, the failed segment is isolated by ring wrap‐back and the ring operates in wrapback mode. When multiple failures occur, the ring is wrapped back further into a smaller ring or several rings until the MAC layer functions are recovered. On the other hand, when the MAC layer functions of the failed segment are recovered, wrapback is released and the failed segment is merged into the active ring. With this reconfiguration mechanism, the largest ring possible to maintain MAC layer functions is formed automatically regardless of failures, powering up or down, etc. This mechanism is represented using finite state machine (FSM) diagrams. The recovery times from multiple failures are evaluated using the specifications of the international LAN standard (ISO 8802‐5). This reconfiguration mechanism has been approved as the IEEE standard (recommended practice) for a dual‐ring reconfiguration mechanism, and its effectiveness has been proven by field trials.
Deterministic tree‐type algorithm with reservation mechanism
Authors: Kawano Hiroyuki , Hasegawa Toshiharu , Nishio Shojiro
Published: July 2007

The tree‐type algorithm has been proposed and investigated widely as a random multiple‐access communication protocol. It is a distributed algorithm but shows a stable throughput performance. Several proposals have been made, including Tsybakov's, for the tree‐type algorithm with a reservation mechanism to improve further the throughput performance.

This paper proposes new TREE‐DTA with reservation mechanism, which is based on the block access method and employs the deterministic Q‐ary tree‐type algorithm operating on the terminal addresses as the retransmission algorithm. The feature of the reservation mechanism proposed in this paper is that the realization is easy, compared to various other methods that have been proposed.

To evaluate the performance of TREE‐DTA with reservation mechanism, a mathematical model is used to derive the approximate expression for the relation between the throughput and the average delay. Furthermore, the performances of TREE‐DTA with reservation mechanism are examined by a simulation experiment. The robustness to the system error and the application of the priority scheme are discussed.
Performance of a controlled capacity digital radio system with diversity reception
Authors: Lee Hee‐Jin , Komaki Shozo , Morinaga Norihiko
Published: July 2007

This paper analyzes the effect of diversity on reducing fading in the controlled capacity digital radio systems. As a result, it is clarified that an improvement of one to three times in the traffic throughput can be obtained if diversity is combined with the controlled capacity system.

Moreover, the performance of the diversity system is compared with the controlled capacity system when both are employed separately and it is made clear that the improvement effects of the controlled capacity system correspond to those of two‐ to four‐fold diversity in fixed‐capacity systems.
Contoured‐beam antenna using smoothly shaped dual‐reflectors for broadcasting satellites
Authors: Shogen Kazuyoshi , Nishida Hayato
Published: July 2007

Previously, the authors have proposed a design method of a shaped dual‐reflector contoured‐beam antenna with virtual multihorns with a view to applications to the broadcast satellite BS‐3. In such a design, there were discontinuities on the main reflector.

In this paper, a method for eliminating these step discontinuities is studied for the dual‐reflectors. The current distribution on the main reflector corresponding to the desired radiation pattern is determined by optimization depending on the constraint gain of the far field. Note that the optimization method for the aperture phase distribution was known for a single smoothly shaped contoured‐beam antenna. Also, in this paper, an optimization method for the amplitude distribution is proposed anew. Further, by adding a restriction to the phase difference between the adjacent elements in the optimization of the phase distribution, the step discontinuity on the reflector is eliminated. By means of this method, an antenna made of a main reflector with an aperture diameter of 2.3 m is designed at 12 GHz which is the frequency of the downlink of the broadcast satellite.

Most of Hokkaido, Honshu, Shikoku, Kyushu, and Okinawa is covered by a radiation pattern with more than 40 dBi and other remote islands with more than 28 dBi. A one‐half scale model is fabricated and the radiation pattern is measured at 22 GHz. The results agree well with the numerical results. Also, the sidelobe and the cross‐polarization characteristics of this antenna sufficiently satisfy the technical standards in RR.AP 30.
Nonblocking atm switching networks for variable bit rate traffic
Authors: Sato Shohei , Akiyama Minoru
Published: July 2007

An asynchronous transfer mode (ATM) switching network handles not only traffic of various bandwidths, but multirate bursty traffic including constant bit rate and variable bit rate traffic as well. Consequently, to simplify the design and operation of the facility, it is desirable for the ATM network to be nonblocking at the connection level. The nonblocking issue when the network must handle variable bit rate traffic is related closely to the connection admission control (CAC) employed.

While the nonblocking feature for a linear CAC function has been studied in the past, the relation between the switching network cell‐level quality and non‐blocking characteristic for a specific CAC premising variable bit rate traffic has not been analyzed.

This paper examines a nonlinear CAC, evaluates the cell loss probability and statistical multiplex gain when it is applied and proposes the definition for a non‐blocking feature called “(p0, p, q) nonblocking.” Next, a cell distribution‐type, three‐stage ATM switching network is shown that ensures (p0, p, q) nonblocking for traffic including multicast connections without expanding the internal link capacity either in terms of space or speed.
Implementation of a communication sdl specification
Authors: Hasegawa Haruo , Tanaka Wataru
Published: July 2007

This paper describes a method of converting a specification and description language (SDL) specification into a program by introducing SDL/OS. The TRON‐specification OS is adopted as OS and C++ as a programming language to make the program portable. SDL/OS, which consists of libraries described in C++, is constructed on OS so that the program converted from SDL can run as it is. SDL/OS realizes the SDL functions easily by using the functions of TRON‐specification OS.

Finally, this paper reports that this method is very effective in enhancement of software productivity by applying it to software development of real communication systems. Moreover, performance degradation can be compensated to some extent by introducing function calls in the same task.
Adaptive array antenna combined with tapped delay line using processing gain for direct‐sequence/spread‐spectrum multiple‐access system
Authors: Wang Hefeng , Kohno Ryuji , Imai Hideki
Published: July 2007

As countermeasures for co‐channel interference from simultaneously accessing users in the spread spectrum multiple access (SSMA), co‐channel interference cancellers using the adaptive digital filters, and array antennas and their combinations have been proposed. However, in these systems, it is necessary to generate a reference signal with a large correlation with the desired wave in receiver so that their coefficients can be updated adaptively. In the SSMA, a method has been proposed in which the reference signal generated by respreading of the demodulated data is used for the updating of the weight coefficient of the array antenna. However, as the input interference and the noise power increase, the convergence of the array antenna becomes difficult. Also, in the conventional method, most of the discussions have been limited to an array antenna in which one weight coefficient corresponds to an array element. However, as the interference signal bandwidth increases, the wideband interference signals cannot sufficiently be removed from the antenna output.

In this paper, from the viewpoint of improving the co‐channel interference elimination capability of the array antenna in the space domain, the reduction of the noise component and the co‐channel interference in the error signal for the array antenna updating is considered and an updating method for an adaptive array antenna using the spread spectrum processing gain is proposed. Further, from the viewpoint of increasing the co‐channel interference elimination capability of the array antenna in the time domain, a receiving system using a TDL (tapped delay line) adaptive array antenna is proposed to increase the frequency characteristics of the bandstop filter for a wideband spread spectrum signal.

Finally, by means of a computer simulation, the basic characteristics of the updating method and the performance of the receiving system are evaluated. It is shown that good characteristics can be obtained under an environment with co‐channel interference and noise power higher than in the conventional system.
A method of moving area‐detection technique in a muse decoder
Authors: Izumi Yoshinori , Gohshi Seiichi , Ninomiya Yuichi
Published: July 2007

Subsampling is used widely in a bandwidth compression of video signals because it simply decreases the sampling rate with less artifacts. The compression efficiency and a final picture quality of a video compression based on a subsampling normally are improved by applying a motion adaptive technique. Such a technique switches processing between the static picture area and moving picture area depending on the movement. This switching is controlled as the result of detecting the moving picture area, a technique called “moving area detection.”

In moving area detection used by a frame‐offset subsampling system such as a MUSE decoder, the frame difference cannot be obtained because the sampled value is omitted by subsampling, thereby causing erroneous detection or detection failure.

In this paper, the improvement of the moving area detection method used in a MUSE decoder, which is the analog transmission system for Hi‐Vision signals, is described as an example of moving area detection of a subsampling system. The improvement of moving area detection is confirmed by an LSI MUSE decoder. The frequency characteristics of a moving area detection circuit also are discussed. Consequently, the frequency characteristics of moving area detection necessary for a MUSE decoder are obtained.
Broadband cylindrical‐cavity directional filter
Authors: Isota Yoji , Miyazaki Moriyasu , Ishida Osami
Published: July 2007

The diplexing bandwidth of a cylindrical‐cavity directional filter is restricted of coupling of the coupling hole, which is installed in order to excite a circular polarization on the common walls of the input and output rectangular waveguides and in the adjacent cylindrical cavity.

This paper proposes a method of increasing the coupling of circular polarization by means of an iris‐loaded cross‐coupling hole (consisting of an iris mounted on the crossed‐coupling hole of a rectangular waveguide). The results of analysis of the magnetic field distribution and the magnetic field intensity in a rectangular waveguide loaded with an iris are described.

It shown that the iris‐loaded cross‐coupling hole is effective in exciting a circular polarization and increasing coupling. The results of a trial fabrication of a directional filter using this type of coupling hole are presented. In the case of a three‐stage maximally flat K band filter, a passband relative bandwidth of 2.7 percent was obtained. This bandwidth is three times as great as in conventional filters. Hence, the range of application of the cylindrical cavity directional filter has been extended.
Measurement of angle of arrival by small circular array antenna for aircraft
Authors: Shirakawa Masayuki , Fukuda Yutaka , Ozeki Shigeru
Published: July 2007

For an airborne collision avoidance system, it is necessary to measure the directions of other aircraft in the vicinity with high accuracy. As one of the methods for such a purpose, a method was studied in which a small circular array and Butler matrix are combined. In such a case, the mutual coupling between the elements increases. However, by adjusting the phases appropriately, it is found possible to maintain a phase relationship in the same way as in the case without mutual coupling. Also, an angular measurement method was proposed in which the outputs of the Butler matrix are combined at the output stage. It was found that the accuracy is close to the one obtained in the maximum likelihood estimator while the circuit is simple.
Virtual path bandwidth control method for ATM networks: Batch modification method
Authors: Shioda Shigeo , Uose Hisao
Published: July 2007

Traffic generated by B‐ISDN services is difficult to predict because the fluctuations in normal traffic patterns are large. As a result, it is difficult to provide network equipment to avoid traffic unbalance. The advantage of using asynchronous transfer mode (ATM) in B‐ISDN networks is that path bandwidth control facilities can be used to dampen the unbalance in traffic.

This paper proposes a new algorithm, based on the batch modification method, for controlling traffic fluctuations. The batch modification method is used to control path bandwidth from a centralized control center. The virtual path bandwidth is calculated using optimization calculations based on information from the entire network. Hence, it is necessary to develop an algorithm to perform the optimization calculations. The algorithm uses the worst case blocking probability and the total amount of traffic. The algorithm is verified with numerical examples that compare traffic patterns in a model network.
FM‐FDM optical CATV system employing demand access technology
Authors: Maeda Mikio , Oyamada Kimiyuki , Ishikawa Tadasu , Fujisawa Syuichi
Published: July 2007

A demand‐access optical CATV system using FM frequency multiplexing is developed. This system allows us to transmit 40 video signals including MUSE high vision signals over 40 km on a single‐mode fiber trunk‐line and can transmit arbitrary four video signals to subscribers at 10 km on subscribers' single‐mode optical fibers. The feature of the present system is the possibility to fabricate an inexpensive hub by using a newly developed channel selector which combines single heterodyne and RF switch and also to make use of a cheap conventional DBS tuner at the subscribers' receiving terminal. For a trunkline, an optical modulation depth has to be carefully determined by considering an inter‐modulation distortion. The present paper describes the degradation in effective CN ratio due to a white noise produced by the FM modulated third‐order distortion and shows an optimum optical modulation depth for a given transmitting distance. Also, a system design is discussed for certain distances of a trunkline and a subscriber line. One can estimate using the present design the CN ratio at a subscriber terminal. The present system can provide the video quality of 4.5 (CN ratio 17.5 dB) for high vision.
Digital loop‐preset synthesizer (dlps) for high‐speed frequency switching
Authors: Tarusawa Yoshiaki , Yamao Yasushi , Saito Shigeki
Published: July 2007

As a method for constructing a new PLL frequency synthesizer allowing high‐speed switching of oscillating frequencies and low power consumption, which has not been existent in the past, a digital loop‐preset frequency synthesizer (DLPS) is proposed. A synthesizer of this construction is applicable to mobile communications wireless equipment for which it has become especially important to make power consumption low.

The DLPS is constructed from the PLL synthesizer circuit and the digital loop‐presetting (DLP) circuit that presets the frequency control voltage and loop phase of the PLL. A method of determining the frequency control voltage by fuzzy prediction is proposed for high‐accuracy presetting. A method of design based on the forementioned construction and analyses of DLPSs having this construction are presented.

Next, DLPSs of the bandwidth of 25 MHz and the frequency step 25 kHz at the 800‐MHz band and 1.5‐GHz band have been trial constructed and these synthesizers are shown to switch the frequency at less than 1 ms, which is two places shorter than the frequency‐switching time of the conventional‐type PLL synthesizers.
Multipath suppression performance of an adaptive array antenna with a systolic array processor
Authors: Ohmiya Manabu , Kawabata Tatsuya , Ogawa Yasutaka , Itoh Kiyohiko
Published: July 2007

This paper describes an adaptive array antenna using a signal processing system which is implemented by a systolic array processor (SAP), SAP‐AA. Computer simulations show the behavior of the SAP‐AA against multipath fading. The SAP realizes a parallel pipelined processing by regularly placing many SAP cells with identical functions and structures so that it achieves the high throughput rate in the data processing. Also, the SAP has many desirable features for very large‐scale integration (VLSI) system design and enables miniaturization, weight reduction, and mass production of the processing equipment.

In this paper, first, the SAP‐AA is described which realizes the least squares (LS) algorithm based on the QR decomposition for the input data matrix using the Givens rotations. In addition, the fundamental performances of the SAP‐AA are studied including both the transient response and the steady‐state behavior in multipath signal environments. To date, there has been no report which treats the multipath signal suppression performance of the SAP‐AA. Finally, it is concluded from the discussion that the SAP‐AA is effective for unwanted signal suppression in a multipath signal environment.
A gram‐schmidt SLC controlling the number of auxiliary antennas to preserve desired signals
Authors: Harasawa Yasuhiro , Kirimoto Tetsuo
Published: July 2007

In the SLC (sidelobe canceler) which automatically suppresses the interference signals received by the side‐lobe of the main antenna, there is a problem of suppression of the desired signal in addition to the interference signal if the desired signal power in the auxiliary antenna is larger than the receiver noise power and if the number of received interference signal is smaller than that of the auxiliary antennas.

In this paper, an SLC is proposed in which the number of auxiliary antennas is adjusted automatically to be equal to that of the interference signals so that the problem of suppression of the desired signal is prevented. It is assumed here that both the desired signal and the interference signals have narrow band widths.

In this SLC, with a view to adjusting the number of auxiliary antennas and the weights at the same time, the Gram‐Schmidt SLC (GS‐SLC) is used so that a sudden change of the input‐output signal power ratio of the Gram‐Schmidt processor is detected and the number of auxiliary antennas are made to coincide with that of the received interference signals. By way of a computer simulation, the fundamental characteristics of the present GS‐SLC are evaluated. It is confirmed that the desired signal preservation property is improved in comparison with the conventional SLC.
Envelope‐controlled digital modulation improving power efficiency of transmitter amplification—application to trellis‐coded 8 psk for mobile radio
Authors: Tomisato Shigeru , Suzuki Hiroshi
Published: July 2007

Trellis‐coded modulation (TCM) has good spectrum properties and excellent bit error rate (BER) performance. This paper presents the envelope control (EC) method which improves the transmitter power amplification efficiency of TCM for mobile radio. Applying EC to TCM leads to two new modulation schemes: smoothed envelope trellis‐coded 8 PSK (SE‐TC8PSK) and constant envelope TC8PSK (CE‐TC8PSK). Modulation and demodulation techniques for SE‐TC8PSK and CE‐TC8PSK are created. The spectrum properties, BER performance, and power‐conversion efficiency of SE‐TC8PSK and CE‐TC8PSK are calculated by computer simulations and compared with those of TC8PSK. EC greatly improves the power‐conversion efficiency at the cost of degrading the spectrum properties and BER performance of both schemes.
Propagation characteristics of tweek atmospherics below anisotropic and inhomogeneous ionosphere models
Authors: Baba Kiyohide , Ohta Kenji , Hayakawa Masashi
Published: July 2007

Tweek atmospherics have been used to estimate the physical quantities of the ionosphere and to understand the propagation mechanism of the waveguide modes due to the propagation characteristics. As the ionosphere, several realistic models which are anisotropic and inhomogeneous are used.

From the theory of the waveguide mode of ionosphere and the ground surface, the propagation characteristics of the tweek atmospheric are evaluated theoretically. The results of the cutoff frequency and the polarization characteristics are compared with the measured data. The cutoff frequency of the first mode of the tweek atmospherics has been found to be very close to the measured value by means of the computation of the phase velocity and the attenuation constant on the actual waveguide in which the electron density profile by Reagan was used.

The polarization of the 0th mode is extremely close to the linear polarization regardless of the electron density profile and agrees well with the measurement. The measured result of the polarization of the first mode is almost completely left‐handed circular at the cutoff frequency. This experimental evidence can be explained by the electron density profile by Reagan. However, it is found that the frequency dependence of the polarization at frequencies higher than the cutoff is substantially different from the measured data. Significant dependence of the polarization characteristics on the electron density profile and the earth's magnetic field suggests that the model of the ionosphere and the propagation characteristics of the waveguide mode can be estimated from the detailed measurement of the polarization.
Use of a human‐body simulator for analysis of MRI antennas
Authors: Ochi Hisaaki , Yamamoto Etsuji , Sawaya Kunio , Adachi Saburo
Published: July 2007

Optimization of an antenna for magnetic resonance imaging (MRI) requires an accurate analysis of antennas loaded by a human body. We have developed a computer code for obtaining the current distribution on the antenna loaded by a human model with an arbitrary geometry and material properties by incorporating the impedance method into the Richmond method. Numerical results for the input impedance are compared with measured impedances confirning the validity of the proposed method. Furthermore, sensitivity. distributions of antennas loaded by a human model are calculated.