Continuous-time high-frequency active filters suitable for monolithic implementation by standard low cost bipolar process are presented. Balanced NIC's are used to cancel out the loss of passive RC integrators, thus realizing active loss-less integrators with good high-frequency performance. Two types of balanced integrators are proposed and their quality factors are analyzed. The proposed NIC-integrators are used to realize tunable active filters capable of low-voltage operation and without the drawbacks of the NIC-gyrator filters. As an example of application of the NIC-integrators to leapfrog simulation of RLC ladders a second-order 1 MHz bandpass filter was designed, computer simulated and laboratory tested showing good results.

A novel condition for complex FIR digital filters to have linear phase is presented. It naturally includes the linear phase conditions for real FIR filters as special cases.

Phase-Locked Loops (PLL's) have been playing an important role in communication systems. In recent years efforts have been shifted toward implementation of the PLL's by means of digital circuits and a number of all digital PLL's (DPLL's) have been proposed to solve the problem of stability in the PLL's. One of the major problems of these DPLL's is the requirement of a high frequency local clock for a good phase lock precision, which inevitably makes it difficult to apply the DPLL's into high frequency operations. In this paper, a DPLL which have a good phase lock precision with a low frequency local clock is proposed. A good phase-lock precision is obtained by small phase control quantum, however, it makes the locking range narrow. Then, frequency control is employed to improve the locking range and a binary quantized phase frequency detector is also described. The relation between clock frequency and performances of the system is analyzed and verified by some experiments. Also, analysis and experimental performance are given for both acquisition behavior and steady-state phase error characteristics with white Gaussian noise present, resulting in that a good phase-lock precision and a wide locking range are obtained with a low frequency clock. The experimental results show a very close agreement with the theoretical results.

The original iterated codes proposed by P. Elias can be regarded as the codes constructed by iterating two dimensional product codes. While the modified product codes have been proposed and shown to be able to increase the rates without increasing the probability of decoding error. On the other hand, we have proposed new codes, called modified iterated codes A, and improved the performance for the original iterated codes by applying the coding and the decoding schemes of the modified product codes to these product codes. It has been proved that the rates of codes A were always much higher than those of the original iterated codes for cross-over probability p0.1617. In this paper, by additionally combining the coding and the decoding schemes of the superimposed codes constructed on the basis of the modified product codes, which are able to increase the rates with the same minimum distance, the performance for codes A can be further improved. We call codes thus constructed modified iterated codes B. It is shown that the rates of codes B are partially higher than those of codes A for p0.0959.

Mode partition noise of a 1.55 µm DFB laser is suppressed by an optical injection locking technique for the first time. The effectiveness is confirmed in a 2.4 Gbit/s, 40 km transmission experiment. This technique completely eleminates the bit-error-rate floor of 10-4.

Some classes of hypercube structure and a routing method for them are presented in this paper. The first class of cyclic permutation networks (CPN1) is constructed by connecting input terminals with output terminals for permutation networks in accordance with a given rule. CPN1 is also a cyclic interchange graph of a hypercube, which is constructed by replacing each edge of the hypercube with a vertex and connecting the new adjacent vertices cyclically. The second class of cyclic permutation networks (CPN2) is constructed by splitting each vertex of CPN1 into two new vertices. The CPN2 is also graph-isomorphic to the CCC network. This paper also presents a routing method using the path coefficient for the cyclic permutation networks and the CCC network. For the cyclic networks, the path coefficient which determines the path from any source node (terminal) to the destination node can be expressed using only the binary representation of the destination node, and does not depend on the representation of the source node.

In this paper, we show that if the spectrum of a frequency modulated (FM) signal is discrete (generally nonuniformly spaced) then the modulating signal is also periodic and-generally-nonuniformly spaced in the frequency demain. In terms of mathematics if an FM signal is almost periodic (a.p.), then the modulating signal is also a.p.

This letter describes a method of estimating the 0 isotherm height in rain, based on analyses of temperature profiles in rain and the Aerological Data of Japan. The derived formula agrees fairly well with the provisional one in the CCIR prediction method of rain attenuation on Earth-space paths.

In many occasions, radio-relay system planners need the data of radio-relay antenna beam bending due to atmospheric refraction. The authors have derived approximate numerical formulas for such atmospheric bending which will facilitate computer calculations.

A new class of active circuits for realization of all-pole low-pass characteristics is proposed. The proposed circuit simulates the doubly terminated ladder filters realized by lossless inductors and lossy capacitors. The number of required operational amplifiers is about two thirds that of the conventional leapfrog realization. First, the synthesis method of an LC ladder filter with lossy capacitors is described. Second, the relations between the voltage and the current of the above-mentioned LC filter are derived and circuits for realizing these relations and a method for synthesizing an odd-order filter are shown. Finally, a fifth-order low-pass filter is designed and it is shown that the measured response shows a good agreement with the theoretical value. Furthermore, the element sensitivity is estimated by a computer and it is shown that the sensitivity of the proposed circuit is lower than that of the conventional leapfrog circuit.

The novel switched-capacitor frequency-to-voltage converter without employing active component is proposed. Therefore, it is free from non-ideal factors of active components, such as offset voltage or open loop gain of op-amps.

This paper develops a closed form approximation method for the mean performance measures in a single-server priority queue with batch arrivals of two classes. The batch arrivals queueing model considered here is an extension of the previously analyzed models and it has a potential applicability in packet communication systems. The interarrival time of batches, batch size (the number of customers) and service time of customers are assumed to have a general distribution for each priority class. The head-of-the-line (HL) and preemptive-resume (PR) rules are considered. Qualitative characterization results are presented through a flow-balance argument. Especially, important relationships between the mean performance measures are derived, which enable us to make an approximation. Using a diffusion approximation for the unfinished work and its refinement, and using the qualitative results, new approximate formulas for the mean performance measures, e.g., mean delay time of each priority class are obtained. Some numerical examples are provided and compared with exact and simulation results, confirming the accuracy of the approximation. The proposed approximate formulas are shown to be exact if the arrival streams for both classes are batch Poisson processes.

Photonic switching and coherent optical transmission would be key technologies for realizing future all optical broadband wide-area networks. This paper reports results of studies on integrating photonic switching systems and coherent optical transmission technologies. Introducing coherent optical transmission technologies to photonic space-division switching systems will lead to some excellent features, including line handling capacity expansion, transmission span increase and integration capability with coherent WDM/FDM broadcasting systems. Photonic wavelength-division (WD) switching systems with large number of WD channels would also be possible, with coherent optical transmission technologies. Space-division switching experiments in a 100 Mb/s optical FSK transmission system were carried out using LiNbO3 photonic switch matrices. Receiver sensitivity improvement of 7.5 dB was observed in the transmission experiments through a photonic switch matrix and long SMFs (22 km, 100 km). This allows more cascaded connection for photonic switch matrices in a photonic switching system. It was also shown that crosstalk component can be rejected at the receiver by introducing channel separation greater than 3 GHz, even when the crosstalk power is ten times larger than the desired signal. From these experimental results, a photonic SD switching system whose line capacity exceeding 500-lines and whose transmission line length was over 20 km, would be expected.

On the basis of the relation between the multichannel prediction model and the 2-D prediction model, the convergence properties of prediction error covariance, prediction coefficients and corresponding 2-D polynomials of the latter model are derived from the known convergence properties of those of the former model. Furthermore, the formulas of the convergence order of the 2-D prediction model are obtained by using the knowledge of the convergence order of 2-D correlation sequence {γi,j}.

We present comparative analysis of average behavior based on path length for hierarchical routing schemes. The analyzed schemes are K-scheme (by Kamoun et al.), G-scheme (by Garcia et al.), and I-scheme (by the authors). The analysis is performed by simulation experiments. The results show that I-scheme is superior to both K- and G-schemes, and that K-scheme is better than G-scheme with respect to path length. Additionally, a path length obtained by I-scheme is about 20% longer than the optimal one on the average.

This paper presents busy/idle signal" scheme for control channel in mobile satellite communication systems. In the design of channel access schemes in mobile satellite communication systems, the following three factors must be taken into account: (1) a control channel is shared by call setup signals and response signals, (2) differences in propagation delays occur depending on the distance between the satellite and the mobile stations, (3) the number of retransmissions of a call setup signal is limited. Traffic performance measures of the proposed channel access scheme, such as throughput, mean setup delay and mean response delay, are compared with those of the random access scheme and the framed access scheme. A numerical method is presented for obtaining these measures, and the method's accuracy is demonstrated by comparing results with those obtained by simulation. This numerical method is very simple and is applicable to channel access schemes for mobile satellite communication systems with the above three factors. Using the numerical method, the proposed scheme is shown to be superior to other schemes.

A disparity detection method with coarse-to-fine strategy using trinocular stereo images is presented. The method employs zero-crossings of the Laplacian of Gaussian filtered images in multiple resolutions as features to make correspondence. An experiment has shown a good result for zero-crossings having an intense gradient.

This paper describes the induction heating system designs for spliced fiber reinforcement and the reinforcement performances. In the case of the reinforcement method using hot-melt adhesive, it is necessary to give the reinforcing assembly the precise temperature distribution. For this reason, the power transfer efficiency from the power source to the work object of the reinforcing assembly was investigated under practical induction heating conditions. Furthermore, the effect of each coil of the induction coils on the magnetic intensity generated in the part of the work object opposite the induction coils was examined. The transient temperature distribution of the work object could be obtained through simulation by designing the proper numbers of turns of wire, the setting positions of the induction coils and the dimension of electric power at a power source. The simulation results agreed approximately with the measured temperatures of the work objects. Through the proper thermal designs, the sandwich and heat-shrinkable-sleeve reinforcements were completed within 1 min., 30 sec. with good performances by supplying less than 26, 12-W of electric powers, respectively.

Variation of bifurcation diagram of difference equation, X (t1) AX (t)(1X (t) BX (t1) ), investigated as a function of B. Several bifurcation patterns appear with B, such as logistic model like pattern, period-3, period-4 and oscillatory pattern.

Parameters of impulsive interference on power line were derived by fitting the observed noise to calculated exceedance probabilities of the envelope. Middleton's class A or B model may be applied to the interference that noise sources are Poissonian distributed on power line and appeared randomly in time. For the periodic and pulsive interference, a simple model is valid.