Surveillance capabilities and operational requirements for future Space-based radar systems are considered. With special attention paid to Air Traffic Control applications, an optimal system architecture is defined. The resulting large antenna dimensions call for novel solutions such as distributed arrays in space.

This letter proposes an active reflector for calibrating a synthetic aperture radar (SAR), in which the frequency of a received SAR signal is shifted by a certain amount and then it is retransmitted to the SAR. The frequency shift causes a shift of the reflector SAR image in an azimuth direction relative to its background. This function would allow to enhance a signal-to-clutter ratio of the reflector image by moving it onto a radiometrically dark background, and hence it would be of value for SAR calibration even in a narrow test site. The theory, design and development are described briefly.

Among the many fabrication methods for oxide superconductor films, metal organic chemical vapor deposition (MOCVD) is particularly suitable for industrial application because of its mass productivity and the low growth temperature. Therefore we have studied this technique using the horizontal cold wall furnace type MOCVD method to obtain high quality superconducting films. As the result, we have succeeded in fabricating YBa2Cu3Oy films which have high critical temperatures (over 80 K) under substrate temperatures as low as 700 without post-annealing. But, in the course of our experiments, it was found that the thicknesses of YBa2Cu3Oy films fabricated by MOCVD were not uniform. The cause of this non-uniformity is believed to be that the deposition rate exponentially falls off along the flow direction because of the decrease of the source gas concentration through the reaction. In this paper, this non-uniformity is analytically studied. It is shown that the deposition rate decrease can be controlled with a tapered inner tube, and that these theoretical results are in good agreement with the results of experiment. In addition, it is indicated that the superconducting property of the films has less dependence on substrate position as a result of the tapered inner tube.

This paper analyzes the performance of an ATM cell multiplexer with a two level MMPP input on a discrete-time basis. We approximated the input process as a simple MMPP model. We developed an MMPP/D/1/K queueing model for the ATM cell multiplexer, and employed an analytic approach for the evaluation of cell loss probability. We verified the accuracy of the results using computer simulation. We applied the above analytic method to connection admission control (CAC) of the ATM network. The resulting connection admission control scheme employs the concept of the "effective bandwidth" and table-look-up procedure. We confirmed through a computer simulation that the proposed connection admission control scheme outperforms the peak bandwidth allocation scheme with respect to link utilization.

The transmission of 8-bit µ-law PCM signals using 16-level weighted QAM over Gaussian channels is examined. The weighting process modifies the positions of the QAM constellation points so that the overall distortion in the recovered information-bearing source signal is reduced. The PCM bits are mapped to the weighted QAM points such that the most significant bits have a lower probability of being in error than the least significant bits. The weighted QAM systems have been optimized for the same energy signal energy per transmitted symbol as for unweighted QAM. Also, the erasure zone is established at the detector, such that if the output falls into the erasure zone, the regenerated sample is replaced by interpolation. The theoretical results indicates that 16-level weighted QAM have a gain of 5dB over unweighted QAM.

As the size and complexity of network increases, the distributed systems management (DSM) will be vital in order to improve the availability of network management, to reduce the complexity of network operations, and to provide the high reliability. In this paper, we (1) describe general requirements required for systems management in distributed environment, (2) introduce the basic structure of distributed network management system (DNMS) for efficient network management, and also especially illustrate the concrete design of system management application process which is an important element among them, (3) propose the connectionless CMIP to accomplish for effectively managing the distributed management system, and indicate its efficiency; this protocol is available to manage dynamically changing DSM environment, to negotiate among the managing systems, to handle the dynamic informations etc. Finally, (4) the behavior and software structure of a suggested management system during negotiation to execute the received request for implementation are presented.

This paper proposes a next-generation narrow-band ISDN (N-ISDN), including a suitable network and network node architecture. The proposed N-ISDN allows every subscriber to use H0/HI-class calls as easily as present telephone calls, and could rapidly expand ISDN services to all the subscribers of a public network. The present status of ISDN is first analyzed then the need for popularization of H0/HI-call services is discussed. The proposed key technologies to popularize HO/HI services are (1) on-chip integration of ISDN switching systems, (2) distribution of small on-chip switching systems over the subscriber switching area, (3) H0-based trunk circuit networks using H0 on-chip switching systems and (4) efficient and flexible call management for 64-kb/s basic-class calls. An estimation of hardware volume of switching nodes is used to show that the proposed architecture is more economical than other possible alternatives, i.e. conventional ISDN and B-ISDN.

The inherent simplicity of the LMS (Least Mean Square) Algorithm has lead to its wide usage. However, it is well known that high speed convergence and low final misadjustment cannot be realized simultaneously by the conventional LMS method. To overcome this trade-off problem, a new adaptive algorithm using Multiple ADF's (Adaptive Digital Filters) is proposed. The proposed algorithm modifies coefficients using multiple gradient vectors of the squared error, which are computed at different points on the performance surface. First, the proposed algorithm using 2 ADF's is discussed. Simulation results show that both high speed convergence and low final misadjustment can be realized. The computation time of this proposed algorithm is nearly as much as that of LMS if parallel processing techniques are used. Moreover, the proposed algorithm using more than 2 ADF's is discussed. It is understood that if more than 2 ADF's are used, further improvement in the convergence speed in not realized, but a reduction of the final misadjustment and an improvement in the stability are realized. Finally, a method which can improve the convergence property in the presence of correlated input is discussed. It is indicated that using priori knowledge and matrix transformation, the convergence property is quite improved even when a strongly correlated signal input is applied.

Generalized telegraphist's equations for waveguides are frequently used for analyzing fields in tapered rectangular waveguides. However, the telegraphist's equations do not give exact fields in E-plane tapers of the rectangular waveguides. In this letter, the new telegraphist's equations are shown, and the equations give the fields which exactly satisfy Maxwell's equations and the boundary conditions for the E-plane taper of the waveguide.

Sandwich-type Josephson junctions with the structure Bi2Sr2Ca1Cu2Ox/Bi2Sr2Cu1Oy/Bi2Sr2Ca1Cu2Oz (BSCCO/BSCO/BSCCO), have been fabricated and their characterstics determined. The BSCO barrier layer, which is characterized by a crystal structure close to that of the BSCCO electrode layer, is a normal conductor at 4.2 K. Superconductor/normal-conductor/superconductor (S/N/S) type current-voltage characteristics are obtained with these junctions. Distinctive Shapiro steps are observed when they are exposed to microwave radiation. An oscillating behavior of each step in their I-V characteristics are confirmed for increased microwave power. The critical current, Ic, is found to be proportional to (1-T/Tc)2 in the neighborhood of Tc. These results coincide with the ones observed with conventional S/N/S junctions.

Experimental results on the superconducting three-terminal devices Using Bi-system High-Tc Superconductors were reported. The VCJJ (Variabel critical-current-type Josephson junction devices) using the thermal effect (VCJJ) and a dual gate Josephson device of a new current-injection type are described. The basic technology and problems for high-Tc three-terminal devices are briefly discussed.

In this paper the three dimensional (3-D) effect on CMOS latch-up is modeled using a graphical technique based on the fundamental principle of "charge neutrality or its current continuity equivalent" in the base region of parasitic transistors involved in latch-up. The graphical generation of the complete latch-up I-V characteristic requires as an input the SPICE parameters of the relevant bipolar and MOS transistors, the values of shunt resistances and the reverse current-voltage characteristic of the well-substrate junction. The infiuence of the MOS transistor shunting the parasitic bipolar transistors has received special attention. The nonideal scaling of the parasitic resistances has been observed to be the most crucial parameter determining the 3-D nature of the device. The proposed model is validated with test-structures fabricated in 2 µm bulk CMOS technology at and above room temperature. SAFE space map is constructed with width W as a parameter.

This paper describes the structure and properties of superconductive small antennas with thin-film matching circuits. These circuits make it possible to realize small antennas, 38 mm20 mm16 mm in size. This is one quarter the length of our previously reported ceramic antennas. The actual gain of this antennas was -4.5 dBi at 470 MHz. This value is 5.5 dB higher than that of Cu antennas with exactly the same structure.

The authors design a simple feed system for a planar slotted waveguide array. A waveguide π-junction with negligible reflection is cascaded to compose a multiple-way power divider. The frequency characteristics of the power divided to each port and the reflection at the feed point are discussed and high performances are predicted. The maximum number of cascaded junctions in this system can be determined in terms of a desired frequency bandwidth and allowable deviation in divided power.

The DSD (Double Soft Decision) concatenated forward error correction scheme is proposed to realize a higher-coding-gain forward error correction system with simple hardware. The novel scheme soft decision decodes inner codes as well as outer codes. In this scheme, likelihood information from an inner Viterbi decoder is used for the decoding of outer codes. Path memory circuit status 1,0 ratio is newly proposed as a measure of likelihood information and it is shown that this method is the most reliable even though it has the simplest hardware among the alternative likelihood information extracting methods. Computer simulation clarifies that the proposed DSD scheme improves Pe performance to one-third that of the conventional hard decision outer decoding.

This paper proposes a new design method of variable FIR digital filters. The method uses a multi-dimensional linearphase FIR filter as a prototype. The principle of the proposed method is based on the fact that the crosssectional characteristics of a 2-D filter along with a line vary if the intersection of this line is changed. The filter characteristics can be varied by recalculating all the filter coefficients from proposed equations, which leads to an advantage that the variable range is very wide. Another advantage is that the passband and stopband deviations are completely predetermined in the design procedures and that the passband edge can be accurately settled to a desired frequency while keeping the transition band width unchanged. First the proposed design method is explained and the effect of the transition band of 2-D filters is discussed. Then the calculation cost required in updating the filter coefficients are considered. Finally two design examples are presented and the proposed method is compared with the existing one, which shows the usefulness of our method.

This paper describes on the transmission properties of the superconducting coplanar waveguide on LiNbO3 (LN) substrates, fabricated by YBa2Cu3Oy (YBCO) superconducting films. The films have been prepared by the reactive co-evaporation method and patterned by a wet etching process. The surface resistance of the obtained film was 0.04 Ω at 18 GHz and 77 K. It was confirmed from X-ray diffraction (XRD) that these films were highly oriented to the direction of c-axis without a secondary phase. The microwave transmission properties of these YBCO coplanar waveguides were investigated at frequencies up to 20 GHz and compared with that of the aluminum coplanar waveguide. The characteristic impedances of both coplanar waveguides were designed to be 50 Ω. It was found that the attenuation constants of these samples at 77 K were less than that of the aluminum coplanar waveguide for frequencies below 18 GHz.

It often occurs in an environmental phenomenon in our daily life that a specific signal is partially or completely contaminated by the additional external noise. In this study, a digital filter for estimating a specific signal fluctuating impulsively under the existence of an actual external noise with various kinds of probability distribution forms is proposed in an improved form of already reported digital filter. The effectivenss of the proposed theory is experimentally confirmed by applying it to the estimation of an actual impulsve signal in a room acoustic.