Macro/microcellular systems have recently been proposed to accommodate both fast and slow moving users. If macrocells and microcells reuse the same frequency band in a macro/microcellular system, the interference between both types of cells can become a critical problem and degrade system capacity, particularly in CDMA systems. In this paper, Frequency Division CDMA (FD-CDMA) is applied to CDMA macro/spot-microcellular systems and uplink capacity is evaluated. The CDMA frequency band is divided into several subbands and both macrocells and microcells reuse the same subbands simultaneously. Interference signals from both types of cells are dispersed by dividing the frequency band, and performance degradation resulting from interference is reduced at both the macrocell and microcell. By reusing the same frequency band for macrocells and microcells, the system capacities become more flexible and can be changed according to variations in traffic. This paper describes the detail of the FD-CDMA system. Uplink capacities are calculated for some cell conditions such as microcell size or location through simulation evaluations. A comparison with a non-reuse subband system as well as results of adaptive control of subbands are described.

New functional surface tunnel transistors (STTs) with multiple interband-tunnel-junctions in a symmetric source-to-drain structure are proposed to reduce the number of fabrication steps and to increase functionality. These devices have p+/n+ interband tunnel junctions in series between a p+ source and a p+ drain through n+ channels. We successfully fabricated GaAs-based multiple-junction STTs (MJ-STTs) using molecular-beam epitaxy regrowth. This fabrication method eliminates the need for two of the photo-masks in the conventional process for asymmetric planar STTs. In the preliminary experiments using multiple-junction p+/n+ diodes, we found that the peak-voltage increment in negative-differential-resistance (NDR) characteristics due to the reverse-biased tunnel junction in negligible, while the first-peak voltage is roughly proportional to the number of forward-biased tunnel junctions. Moreover, the number of NDR characteristics are completely determined by the number of tunnel junctions. The fabricated STTs with multiple junctions, up to eight junctions, exhibited clear transistor operation with multiple NDR characteristics, which were symmetric with the drain bias. These results indicate that any number of gate-controlled NDR characteristics can be realized in MJ-STTs by using an appropriate number of tunnel junctions in series. In addition, as an example of a functional circuit using MJ-STTs, we implemented a tri-stable circuit with a four-junction STT and a load resistor connected in series. The tri-stable operation was confirmed by applying a combination of a reset pulse and a set pulse for each stable point.

In this paper a novel narrow-band bandpass filter with an output pair of analytic signals is presented. Since it is based on the complex analog filter, both synthesis and response characteristics of this filter are different from conventional bandpass filters. In the design of this filter, the frequency shift method is employed and the conventional lowpass to bandpass frequency transformation is not required. The analysis and examples show that the output signal pair of the proposed filter possesses same filtering characteristics and a 90 degree phase shifting characteristics in the passband. Therefore, the proposed filter will be used for a single sideband (SSB) signal generator without quadrature generator.

Fiber optic subcarrier transmission system using coherence multiplexing techniques for broad-band distribution networks is proposed. This system makes it possible to improve the laser linewidth requirement and also to eliminate the effect of intermodulation distortion (IMD) which is serious problem in subcarrier multiplexed (SCM) system. In the proposed system, the frequency difference, fo, between the reference light and the signal light makes it possible to generate the broadand FM signal after photodetecting. Thus, an increase in the modulation index provides a corresponding increase in receiver sensitivity. We analyze the fundamental performance of the proposed system and derive the signal-to-noise ratio (SNR) at the output of FM demodulator by taking the threshold effect and spike noise into account. The proposed system can achieve the total capacity in excess of 10 GHz, and thus it is attractive for multichannel broad-band distribution networks.

This paper describes the design, fabrication, and performance of a C- to Ku-band 2 W balanced amplifier multi-chip module employing an MMIC/Super-MIC/MIC configuration. In this module, single-ended amplifiers, quadrature couplers, and pulsed-drive circuits are fabricated on MMICs, Super-MICs, and MICs, respectively, which show different features in fabrication, performance, size, and cost. With the use of the distinguished features of MMICs, Super-MICs, and MICs, the multi-chip module with high performance, small size, and low cost has been achieved. The MMIC/Super-MIC/MIC-combined module would be a candidate for a variety of multi-chip modules with stringent requirements for performance, size, and cost.

Theoretical values of site attenuation for broadband receiving antenna or the antenna factor of broadband antenna over the frequency range from 30 MHz to 1 GHz have been calculated or measured by some researchers. For a frequency range over 1 GHz, wire antennas or horn antennas should be used. However, the theoretical site attenuation or antenna factor over 1 GHz have never yet been calculated. A CLS (Conical Log-periodic Spiral) antenna is generally used for EMC/EMI measurements in the microwave band as a broadband wire antenna for the swept frequency method. However, this antenna has the defect that its use results in the loss of polarization information. So we proposed an improved CLS antenna which has linear polarization. This new CLS antenna has another wire wound symmetrically to that of the standard CLS antenna. For this reason, we named it a double-wire CLS antenna. The double-wire CLS antenna loses no polarization information. We calculated the height pattern and the frequency characteristics of CSA (Classical Site Attenuation) for the double-wire CLS antenna when used for receiving, or used for both transmitting and receiving, as well as the antenna factor. Moreover, NSA (Normalized Site Attenuation) when the double-wire CLS antenna is used for receiving or used for both transmitting and receiving in free space were calculated.

The defects in the cold rolled strips have textural characteristics, which are nonuniform due to its irregularities and deformities in geometrical appearance. In order to handle the textural characteristics of images with defects, this paper proposes a surface inspection method based on textural feature extraction using the wavelet transform. The wavelet transform is employed to extract local features from textural images with defects both in the frequency and in the spatial domain. To extract features effectively, an adaptive wavelet packet scheme is developed, in which the optimum number of features are produced automatically through subband coding gain. The energies for all subbands of the optimal quadtree of the adaptive wavelet packet algorithm and four entropy features in the level one LL subband, which correspond to the local features in the spatial domain, are extracted. A neural network is used to classify the defects of these features. Experiments with real image data show good training and generalization performances of the proposed method.

In this paper, we present a novel way to design biorthogonal and paraunitary linear phase filter banks. The square error of the perfect reconstruction of the filter bank is expressed in quadratic form of filter coefficients and the cost function is minimized by solving linear equation iteratively without nonlinear optimization. With some modifications, this method is extended to the design of paraunitary filter banks. Furthermore, the lattice structure of odd-channel paraunitary filter banks is also derived. Design examples are given to validate the proposed method.

A 2.4 GHz band direct sequence (DS) spread spectrum (SS) radio frequency modem with a wide bandwidth of 26 MHz in half-duplex system has been newly developed using the small size (832 mm) and highly-efficient (-57 dBm) elastic type of surface acoustic wave (SAW) convolver. The size of SS modem is 905011 mm and the weight is 75 g. The power consumption of SS modem is 1.5 W and data rate is 206 kbps with 63 chips of PN code. Electrical characteristics measurements were made to evaluate the SS modem performance.

A method called "active guard band filtering" is proposed for reducing substrate noise in analog and digital mixed-signal integrated circuits. A noise cancellation signal having an inverse value to the substrate noise is actively input into a guard band to suppress the substrate noise. An operational amplifier produces the noise cancellation signal based upon the substrate noise detected by one guard band and feeds this signal through another quard band into the substrate. This is done within the amplifier feedback loop, which includes the guard bands and the substrate. The noise suppression effect was measured by using 0.8µm CMOS test chip. Using active guard band filtering suppressed substrate noise to -40 dB of the original non-canceled noise level at 8 MHz. The noise suppression effect was also observed at frequencies up to 20MHz, with an external operational amplifier. The influence of parasitic impedance was found to be a key factor in noise suppression. An active guard band filter with an on-chip noise cancellation circuit will be even more effective for high frequencies, because it eliminates parasitic impedance due to external components.

In this paper, we introduce a VP rearrangement scheme to realize the dynamic control of ATM network. We demonstrate its effectiveness for the transport of B-ISDN traffic which is both fluctuous and hard to predict. First, we present a strategy for the ATM network provisioning, used to manage both the logical VP network and the underlying physical transport network. We then propose a VP rearrangement scheme and discuss its performance. Lastly, we analyze the proposed scheme by simulations, and confirm that its performance, in comparison to the conventional, dynamic VP bandwidth control scheme, is superior.

Digital-switching noise coupled into sensitive analog circuits is a critical problem in large-scale integration of mixed analog and digital circuits. This paper describes noise coupling of this kind, especially, through the substrate in CMOS integrated circuits, and reviews recent technical solutions to this noise problem. Simplified models have been developed to simulate the substrate coupling rapidly and accurately. A method using a CMOS comparator was proposed for measuring the effects of substrate noise, and equivalent waveforms of actual substrate noise were obtained. A circuit tecnique, called active guard band filtering, that controls the noise source is a new approach to substrate noise decoupling. CAD methods for handling substrate-coupled switching noise are making design verification possible for practical mixed-signal LSIs.

The Virtual Path (VP) concept is one of the versatile features of ATM/B-ISDN. Using the VP concept, a bundle of virtual circuits can be grouped together between any two switching nodes in the network. Further, the VP bandwidth and routing can be dynamic. Building on this idea, a dynamically reconfigurable, dynamic call routing wide area (backbone) broadband network concept is proposed. Specifically, this provides dynamism at two levels: at the VP level and at the connection level. For an incoming connection request, at most two logical virtual path connections (VPCs) are allowed between the origin and the destination; these logical VPCs are defined by setting virtual paths links (VPLs) which are, in turn, physically mapped to the transmission network. Based on the traffic pattern during the day, the bandwidth of such VPCs and their routing, as well as call routing, changes so that the maximum number of connection requests can be granted while maintaining acceptable quality of service (QoS) for various services. Within this framework, we present a mathematical model for network design (dimensioning) taking into account the variation of traffic during the day in a heterogeneous multi-service environment. We present computational results for various cost parameter values to show the effectiveness of such networks compared to static-VP based networks in terms of network cost.

Many efforts are currently underway to design wideband mobile communication systems. In this letter, we clarify the received signal level characteristics for wideband mobile radio channels in line-of-sight (LOS) microcells. We conduct several urban-area field experiments to measure the received signal levels for various receiver bandwidths from 300 kHz to 30 MHz and the power delay profile. The experimental results show that the fading depth of the received signal decreases as the normalized rms delay spread, defined as the product of receiver bandwidth and rms delay spread, increases. These results are useful in designing wideband microcell systems for urban areas.

A new structure for adaptive AR spectral estimation based on multi-band decomposition of the linear prediction error is introduced and the mathematical background for the soulution of the related adaptive filtering problem is derived. The presented structure gives rise to AR spectral estimates that represent the true underlying spectrum with better fidelity than conventional LS methods by allowing an arbitrary trade-off between variance of spectral estimates and tracking ability of the estimator along the frequency spectrum. The linear prediction error is decomposed through a filter bank and components of each band are analyzed by different window lengths, allowing long windows to track slowly varying signals and short windows to observe fastly varying components. The correlation matrix of the input signal is shown to satisfy both time-update and order-update properties for rectangular windowing functions, and an RLS algorithm based on each property is presented. Adaptive forward and backward relations are used to derive a mathematical framework that serves as a basis for the design of fast RLS alogorithms. Also, computer experiments comparing the performance of conventional and the proposed multi-band methods are depicted and discussed.

This paper discusses the problems in designing virtual-path (VP) networks and underlying transmission-path (TP) networks using the "self-sizing" capability. Self-sizing implies an autonomous adjustment mechanism for VP bandwidths based on traffic conditions observed in real time. The notion of "bandwidth demand" has been introduced to overcome some of the problems with VP bandwidth sizing, e.g., complex traffic statistics and diverse quality of service requirements. Using the bandwidth demand concept, a VP-bandwidth-sizing procedure is proposed in which real-time estimates of VP bandwidth demand and successive VP bandwidth allocation are jointly utilized. Next, TP bandwidth demand, including extra capacity to cover single-link failures, is defined and used to measure the congestion level of the TP. Finally, a TP provisioning method is proposed that uses TP "lifetime" analysis.

It has been known that an N-vertex binary tree can be embedded into the path and grid with dilation O(N/logN) and O((N/logN)), respectively. This paper shows that an N-vertex binary tree with proper pathwidth at most k can be embedded into the path grid with dilation O(N/N1/k) and O((N/N1/2k)), respectively.

Banyan networks are used in multiprocessor computer applications for an ATM switching. In this paper, we study the continuous blocking of the first n-stage which makes the performance of the banyan networks decrease. We use the 2-dilated banyan networks into the banyan networks to remove the continuous blocking of the first n-stage. We call the new networks as the hybrid dilated banyan networks. We explain how to analyze the throughput of this networks at each stage. Based on the analysis of input rate and output rate at each stage, we can design the hybrid dilated banyan networks with the desirable output rate. The result of analysis shows the hybrid dilated banyan networks have higher performance and feasibility than the banyan networks.

As a result of increasing demand and regulatory changes, access systems are undergoing significant expansion. Although wireless and copper-based systems are being deployed, fiber access systems provide the best conduit for broadband services. Significant deployment and trials of Hybrid Fiber-Coax (HFC) and Switched Digital Video (SDV) systems are underway, and additional architectures are being considered for future upgraded networks. We review the progress in this field, and indicate where enabling device technologies can provide key functions.

This paper is concened with the design and implementation of a 2-channel, 2-dimensional filter bank using rectangular (analog/digital) and quincunx (digital/digital) sampling. The associated analog low-pass filters are separable where as the digital low-pass filters are non-separable for a minimum sampling density requirement. The digital low-pass filters are Butterworth type filters, N = 9, realized as LWDFs. They, when itterated, approximate a valid scaling function (raised-consine scaling function). The obtained system can be used to compute a discrete wavelet transform.