摘要:

AbstractThe wavelength generated by a single mode distribution feedback (DFB) laser varies over time inside pulses generated at high modulation speeds (chirp). This worsens the transmission characteristics of a long‐distance communication link that uses the laser as a light source. Because the modulation of the DFB laser is used to produce a pulse train signal to be transmitted, it is important to determine the dependence of the wavelength fluctuation on the modulated pulse pattern. The dependence of the chirp on the pulse pattern and its degrading effect on the transmission characteristics will be demonstrated here. It will be shown that the pulse pattern dependent wavelength fluctuation is due both to temperature variations caused by the pulse density and carrier storage effects at gigabit per second order modulation speed. The carrier storage effect of the pattern on the wavelength dependence can be reduced by increasing the bias current above the threshold value. However, raising the bias current does not improve the thermal dependent wavelength fluctuation. For example, it will be shown that for a modulation current of 90 mA, the generated center wavelength varies on the order of 0.08 nm. A model for the degradation of the transmission characteristics due to the wavelength fluctuation of the light source through the interaction with chromatic dispersion in the fiber will be presented. Degradation will be quantified experimentally and analyticall

ISSN:8756-6621    

DOI:10.1002/ecja.4410790101

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

年代:1996

数据来源: WILEY

摘要:

AbstractThis paper discusses capacity expansion problems for telecommunication network facilities, based on fuzzy dynamic programming. Although cost functions, discount rates, demand functions, and so on should be given, they usually cannot be defined clearly because of technical developments or business fluctuations. This paper represents undefined factors by fuzzy numbers with triangular membership functions (TFN). Multiplication or division of TFN does not give rigid TFN, but we approximate them to TFN for ease of calculation. Three methods based on this approximation are compared, using numerical examples. Approximation accuracies are confirmed by strict calculation using removal of defining orders of fuzzy numbers.

ISSN:8756-6621    

DOI:10.1002/ecja.4410790102

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

年代:1996

数据来源: WILEY

摘要:

AbstractA method for designing an amplifier that does not need an RF choke coil is proposed. This is accomplished by adding a shunt capacitor to a class E amplifier with a shunt inductor; this creates class E switching where higher harmonics are induced in the inductor‐fed input waveform. A design method is derived by performing an analysis of the circuit assuming load current is sinusoidal. Because the switch current is smaller than that of conventional class E amplifiers (with the same output power), the losses due to the series saturation resistance of the switch device are greatly reduced for the proposed amplifier. A 96‐percent RF conversion efficiency for 2 W of output power was obtained in experiments using a 2‐MHz switch using the proposed d

ISSN:8756-6621    

DOI:10.1002/ecja.4410790103

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

年代:1996

数据来源: WILEY

摘要:

AbstractWhen broadband integrated services digital network (B‐ISDN) service is implemented, the choice of a routing algorithm for broadcast services will be an important issue. Routing is the problem of deciding which of several nodes already connected to the broadcast node will be advantageous for the connection of new calls. In this respect, the number of viewers on each node would be important information. This paper uses broadcast traffic simulations to examine a method for determining a change in the number of viewers with the minimum number of calculations. The conventional approach would calculate the call transitions until the desired moment, but here the goal is to shorten the calculation time by determining the number of viewers directly at the desired moment. In this examination, under the two conditionsM(N)/M/NandN, M(N)/D/N, two models are proposed for the duration of the ON state of the node (a situation where there is more than one viewer): the exponential distribution approximation and the hypercharacteristic distribution approximation. The number of viewers is modeled by the birth‐death process approximation and the normal distribution approximation. The amount of time needed for the calculation depends on the interval to calculate the traffic intensity and the number of viewers, but this is much less than the time needed when the conventional method is u

ISSN:8756-6621    

DOI:10.1002/ecja.4410790104

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

年代:1996

数据来源: WILEY

摘要:

AbstractA mobile packet communication with a chained isolated radio zone network system is proposed that provides nonrealtime media services including voice messages, images, and navigation information, etc., to terminals in cars. In this system, microradio zones are located along a road to establish the communication between a radio base station and a terminal by using packets in a common format. A terminal receives the signal by the paging channel covering a wide area and transmits packets sequentially when a terminal passes radio zones. Therefore, only three radio frequencies, inbound, outbound, and paging channels, are enough and location registration of all terminals is not necessary to realize the proposed system. When transmission and reception of multiple packets is not completed in a single radio zone, it can be done in other radio zones. Since every terminal has a different staying time in each radio zone, the relationship between staying time and throughput, and the relationship between staying time and message transmission ratio are examined and evaluated by the simulation.

ISSN:8756-6621    

DOI:10.1002/ecja.4410790105

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

年代:1996

数据来源: WILEY

摘要:

AbstractIn the quasi‐millimeter radio access system, the links are installed radially from the central station (CS) to the outstation (OS). Therefore, the interference characteristics of the CS are deteriorated at the time of rain.This paper proposes a transmission power control method with a view to reducing the deterioration of the interference characteristics at the CS in rain. The effect of compensation of the level ratio of a desired wave to an undesired wave (D/U) degradation at the CS in the rain can be reduced by 11.5 dB by the transmission power control (TPC) of 20 dB. Further, the speed of the rain attenuation was found which is a propagation parameter needed for the TPC. The trailing speed of the rain attenuation in the proposed TPC algorithm is 67 dB/s, which is much larger than the maximum speed of the 3 dB/s of the rain attenuation. Hence, the proposed TPC algorithm can sufficiently follow the rain attenuatio

ISSN:8756-6621    

DOI:10.1002/ecja.4410790106

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

年代:1996

数据来源: WILEY

摘要:

AbstractOne of the important technologies in the pulsed radar is the pulse compression by means of chirp signals. This technology simultaneously satisfies the contradicting requirements of increased search distance, or the increase of the average transmission power, and of range resolution. However, the waveform after pulse compression has a range sidelobe in the range direction and a small object existing near an object with a large radar cross section is hidden in the range sidelobe so that its detection becomes difficult.To suppress the range sidelobes, a method has been considered to provide weights to the frequency characteristics of the pulse compression radar. In this paper, the wavelet transform as a tool for time frequency analysis is used for the analysis of pulse compression waveform. A range sidelobe suppression method in which a filter with a wavelet localized on the time and frequency axis as an impulse response is placed behind the compression filter is proposed since the frequency components near the main lobe and near the sidelobes are different. In this method, the local weighting is carried out.As a result of the convolution of the pulse compressed waveform with the wavelet with a scale corresponding to the frequency components near the main lobe, i.e., the filtering, it is shown by computer simulation that the correlation is reduced in the range sidelobe region and the maximum sidelobe level is reduced by about 10 dB. The proposed method can be combined with the weighting of the frequency characteristics of the pulse compression filter. Further, the dc offset of the I/Q signal can be eliminated.

ISSN:8756-6621    

DOI:10.1002/ecja.4410790107

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

年代:1996

数据来源: WILEY

摘要:

AbstractRecently, differentially encoded 16 amplitude/phase shift keying (16 DAPSK) has been investigated intensively for mobile radio applications. Since the bit error rate (BER) performance of differential detection (DD) is inferior to that of coherent detection (CD), multisymbol DD of 16 DAPSK has been proposed. However, as the observation interval of multisymbol DD is increased to improve the BER performance, computational complexity increases.In this paper, the differential detection scheme of 16 DAPSK based on the maximum likelihood sequence estimation (MLSE) using Viterbi algorithm is proposed and the BER performance of the proposed scheme is investigated by computer simulation. It is shown that the BER performance of Viterbi‐decoding DD outperforms that of three‐symbol DD without increasing the computational complex

ISSN:8756-6621    

DOI:10.1002/ecja.4410790108

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

年代:1996

数据来源: WILEY

摘要:

AbstractThe maximum‐likelihood sequence estimation reception system, where the transmitted signal sequence is decided by the maximum likelihood using Viterbi algorithm, from the modulated signal, such as the phase modulated convolution‐coded signal, TCM, and CPM, is considered to be very interesting because of its excellent signal‐to‐noise ratio (SNR) versus error rate performance. Such a system assumes the coherent detection of the received signal in order to realize excellent performance. The reception system, which is expected to follow the carrier with a large offset and a low SNR, has been difficult to realize due to the difficulty of satisfying the requirement. This paper proposes the following system. The phase‐locked loop is provided corresponding to each survival path in the Viterbi algorithm used in the estimation of the maximum‐likelihood sequence estimation. The phase‐locked loop is selected in parallel to the selection of the survived path. In other words, the phase synchronization and the (maximum‐likelihood) sequence estimation are simultaneously achieved. The system is discussed in detail, and it is shown that a stable coherent detection can be realized for

ISSN:8756-6621    

DOI:10.1002/ecja.4410790109

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

年代:1996

数据来源: WILEY

摘要:

AbstractWhen more than one satellite is operated nominally at the same longitude of the stationary orbit, there is a danger of collision. At present, to avoid the collision, the cooperative station‐keeping is applied so that the spacing of the satellite orbits is maintained as evenly as possible. In this method, however, it is difficult to cope with the situation when a larger number of satellites is operated at the same longitude in the future. From such a viewpoint, it is intended to apply the relative orbit determination by the differential angle tracking to the orbit monitoring of multiple satellites.An experiment for accuracy evaluation is executed using the satellites in operation. The position of the satellite, which is to be used as the reference in the evaluation, is calculated by calibrating the present orbit‐determination system. The orbit is calibrated by observing the close satellites by a large telescope on the same scene and measuring accurately the differential angle between the two satellites. The accuracy of the relative orbit determination is evaluated by the differential angle measurement using the calibrated orbit‐determination system and it is seen that the relative position of the two satellites can be estimated with the accuracy of 1 km. In other words, it is seen that the relative orbit determination by differential angle tracking can be executed practically for monitoring the approach of satel

ISSN:8756-6621    

DOI:10.1002/ecja.4410790110

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

年代:1996

数据来源: WILEY