This paper deals with a design problem of an observer-based robust preview control system for uncertain discrete-time systems. In this approach, we adopt 2-stage design scheme and we derive an observer-based robust controller with integral and preview actions such that a disturbance attenuation level is satisfactorily small for allowable uncertainties.

This paper reports on a fiber-optic system for in-building wireless communication/broadcast systems developed in Samsung Electronics. Our system delivers the third generation mobile system, satellite-digital multimedia broadcast, and wireless local access network services over a single strand of single-mode fiber or multi-mode fiber. We present the design issue and experimental results of the radio-over-fiber link.

We suggest a new minimum credit method for the dynamic bandwidth allocation in EPON. In the suggested method, to eliminate the unused transmission time-slot, each ONU requests no more than a predetermined maximum. We analyze the upstream channel resource wastage when traffic is light. Based on the analysis, we derive a minimum credit that eliminate the upstream channel resource wastage. The OLT estimates a traffic load and grants a minimum credit when the request is smaller than the minimum credit and traffic is light. Using simulation, we show the minimum credit discipline is superior than the existing methods in the mean delay and the frame loss rate.

The cascade of two baseline networks in tandem is a rearrangeable network. The cascade of two omega networks appended with a certain interconnection pattern is also rearrangeable. These belong to the general problem: for what banyan-type network (i.e., bit-permuting unique-routing network) is the tandem cascade a rearrangeable network? We relate the problem to the trace and guide of banyan-type networks. Let τ denote the trace permutation of a 2n2n banyan-type network and γ the guide permutation of it. This paper proves that rearrangeability of the tandem cascade of the network is solely determined by the transposition τγ-1. Such a permutation is said to be tandem rearrangeable when the tandem cascade is indeed rearrangeable. We identify a few tandem rearrangeable permutations, each implying the rearrangeability of the tandem cascade of a wide class of banyan-type networks.

Novel dual-band bandpass filter (BPF) with quasi-elliptic function response by using the meander coupled step-impedance resonators (SIRs) is presented. By tuning the appropriate impedance ratio (K) and physical length of SIRs, the BPF has good dual-band performance at 2.4 and 5.2 GHz with high selectivity, due to the transmission zeros appeared in two passband edges. Measured results of the proposed BPF have a good agreement with the electromagnetic (EM) simulated results.

The UWB (ultra-wideband) pulse radar is a promising candidate as an environment measurement method for rescue robots. Radar imaging to locate a nearby target is known as an ill-posed inverse problem, on which various studies have been done. However, conventional algorithms require long computational time, which makes it difficult to apply them to real-time operations of robots. We have proposed a fast radar imaging algorithm, the SEABED algorithm, for UWB pulse radars. This algorithm is based on a reversible transform, BST (Boundary Scattering Transform), between the target shape and the observed data. This transform enables us to estimate target shapes quickly and accurately in a noiseless environment. However, in a noisy environment the image estimated by the SEABED algorithm is degraded because BST utilizes differential operations. We have also proposed an image stabilization method, which utilizes the upper bound of the smoothness of received data. This method can be applied only to convex objects, not to concave ones. In this paper, we propose a fractional BST, which is obtained by expanding the conventional BST, and an image stabilization method by using the fractional BST. We show that the estimated image can be stabilized regardless of the shape of target.

A Non-Uniform Discrete Multitone (DMT) transceiver employing an octave spaced quadrature mirror filter (QMF) bank, can be used to overcome the problem of channel noise enhancement in the zero-forcing (ZF) equalization technique. In this letter, performance of the Non-Uniform DMT system is analyzed. A study of the crosstalk between sub-channels due to non-ideal filter banks is also presented. Crosstalk analysis is based upon the bit error rate (BER) performance versus the QMF order in a standadard ADSL channel. Performance comparison of the Non-Uniform DMT transceiver and a conventional DMT system is given, and it is shown that the Non-Uniform DMT transceiver displays slight improvement over the conventional DMT system for the filters of higher order.

We consider the bandwidth optimization problem in a Generalized Processor Sharing (GPS) server to minimize the total bandwidth such that QoS requirements for each class queue are satisfied. Our previous optimization algorithm [6] requires rather long optimization time to solve the problem. We propose a new optimization algorithm based on weight vector adjustment. Numerical results show that the required time to find the optimal resource in GPS servers is significantly reduced, compared to the previous algorithm.

Under the broadband-ubiquitous environment, digital content creation/distribution will be the key factor to activating new industries. This paper first describes the impact of a broadband-ubiquitous environment on digital content creation/distribution; then it proposes new models for digital content creation/distribution businesses. In a broadband-ubiquitous environment, the key is creation of moving picture content; thus the paper describes a system that allows non-CG experts to make CG movies easily.

Recently, spiral inductors have widely been used instead of resistors in the design of matching circuits to enhance the thermal noise performance of a wireless transceiver. However, such elements usually have low quality factor (Q) and may encounter the self-resonance in microwave-frequency band which permits its use in higher frequencies, and on the other hand, they occupy the large on-chip space. This paper presents a new design theory for the impedance-matching circuits for a single-chip SiGe BiCMOS receiver front-end for 2.4 GHz-band wireless LAN (IEEE 802.11b). The presented matching circuits are composed of conductor-backed coplanar waveguide (CPW) meander-line resonators and impedance (K) inverter. The prototype front-end receiver is designed, fabricated and tested. A few of the measured results to verify the design theory are presented.

A novel structure of bandpass filter using NRD guide E-plane resonators is proposed. The NRD guide E-plane resonator is constructed by inserting metal foils in the E-plane of NRD guide. Simulation, fabrication and handling of the filter are very easy because each resonator is separated by simple metal foils. Chebyshev response bandpass filters are designed based on the theory of direct-coupled resonator filters and fabricated at 60 GHz. Simulated and measured filter performances agreed well with the design specifications. Insertion losses of the fabricated filters were found to be around 0.3 dB for 3-pole filter and 0.5 dB for 5-pole bandpass filter, respectively.

A novel wideband bandpass filter with improved stopband characteristics is presented in this paper. Dual-mode square ring resonator is used in the proposed filter. New formulas based on the even- and odd-mode analysis are derived to facilitate the design of transmission zeros of the square ring resonator. A short-circuited stub and a piece of aperture-enhanced parallel-coupled lines are introduced to the input and output of the resonator to lower the passband return loss and widen the stopband of the filter significantly. The filter has a 50% fractional bandwidth, is compact in configuration, and shows remarkably improved performance compared with previously reported filters of the same kind. The measured filtering response shows a good agreement with the simulated result.

In the design of an active integrated antenna, it is necessary to analyze problems such as unwanted emissions or mutual coupling between elements. In this paper, we clarify the problems in implementing S-parameters for an FDTD analysis. Cubic spline interpolation is suitable for the construction of the S-parameter data. The implementation methods of terminal resistors and vias are examined. The proposed FDTD analysis becomes stable after correcting the discrete time lag in the formation of the incident wave. The validity of the proposed method is verified in its application to the low pass filter and the frequency tunable band pass filter.

Recently, the number of multi-homed hosts is getting large, which are equipped with multiple network interfaces to support multiple IP addresses. Although there are several proposals that aim at bandwidth aggregation for multi-homed hosts, few of them support mobility. This paper proposes a new framework called AMS: Aggregate-bandwidth Multi-homing Support. AMS provides functions of not only bandwidth aggregation but also mobility by responding to the changes of the number of connections during communication without the support of underlying infrastructure. To achieve efficient data transmission, AMS introduces a function called address pairs selection to select an optimal combination of addresses of the peer nodes. We implemented AMS in the kernel of NetBSD and evaluated it in our test network, in which dummynet was used to control bandwidth and delay. The measured results showed that AMS achieved ideal bandwidth aggregation in three TCP connections by selecting optimal address pairs.

This paper overviews the history of a class of varactor tuned bandpass filters. Since the miniaturization as well as the high performance of the tunable bandpass filters is required for the next generation mobile communication systems, the discussion is focused on the various planar type tunable filters including active configurations. Brief design concepts of various tunable filter configurations as well as their characteristics are discussed.

This paper presents novel multi-band equilateral triangular microstrip antennas (ET-MSAs) fed by an L-shaped feeding probe. Two types of the ET-MSA are proposed in this paper; they are ET-MSA with closed folded slots and open folded slots with an embedded bridge. The antenna prototypes presented in this paper assume four folded slots in which a metal strip is inserted to realize a good multi-band performance. In addition, the open folded slots, in which the metal strip inside the folded slot is connected to the ET-MSA by the embedded metal bridge, leads to miniaturize the antenna. The proposed antennas are printed on the top layer of a PTFE substrate while the L-probe is printed on the bottom one. The L-shaped probe is utilized due to its tremendous performance in providing a wideband impedance matching. Five resonant frequencies of the ET-MSAs with closed folded slots and with open folded slots are predicted by the electromagnetic simulator (IE3D) based on the method of moment, respectively. Some parametric studies have been also investigated to meet an appropriate multi-band performance. A broadside radiation pattern and gain of 3.0-7.0 dBi have been confirmed by the measurement for the entire observed frequencies. Measured results agree well with the prediction. Thus, these antenna systems are demonstrated to be useful models for a multi-band planar antenna.

This paper proposes a new microstrip stepped-impedance resonator (SIR) used for bandpass filters with reduced size and improved stopband characteristics. A comprehensive treatment of both ends of the resonator with loaded triangular and rectangular microstrips is described. The design concept is demonstrated by two filter examples including four-resonator parallel-coupled Chebyshev bandpass and compact four-resonator cross-coupled elliptic-type filters. These filters are not only compact size due to the slow-wave effect, but also have a wider upper stopband resulting from the resonator bandstop characteristic. The filter designs are described in details. The simulated and experimental results are demonstrated and discussed.

An InGaP/GaAs HBT MMIC amplifier with an active balun has been developed for ultra-wideband radio systems (UWB). The MMIC was designed to drive a self-complementary antenna with a balanced mode, where an input impedance is 60π ohms. The MMIC consists of a common mode negative feed back ultra-wideband amplifier circuit, an active balun circuit, and a high impedance drive circuit. The developed amplifier provides a 3-dB gain roll-off bandwidth from 2.4 GHz to 10.8 GHz with a 14.1-dB linear power gain, and a linear power output up to 3 dBm. The developed amplifier with the active balun provides a 3-dB gain roll-off bandwidth from 2.3 GHz to 8.6 GHz with a 21.3-dB power gain in a balanced mode, and a linear power output up to 0.6 dBm. The measured total group delay is less than 32 psec. Output signals at the balanced output terminals of the MMIC were kept inverted with a steep pulse shape for an impulse input signal of 57-psec pulse width.

A novel linear transconductor using translinear cells is proposed. It consists of a voltage follower, a resistor, and a current follower. SPICE simulations using an 8 GHz bipolar transistor-array parameter show that the linear transconductor with a transconductance of 1 mS exhibits a linearity error of less than 0.75% over an input voltage range of 1 V for a supply voltage of 2.0 V. The temperature coefficient of the transconductance is less than 124 ppm/. The -3-dB frequency of the transconductance is more than 4.5 GHz. Applying the linear transconductor as a building block, the design of a bandpass filter with center frequency of 85 MHz and Q-factor of 80 is presented.

This paper proposes a new method which simultaneously undertakes ranging and communications based on the PHY of MB-OFDM technology. A transmitter modulated one or multiple OFDM subcarriers with a low-frequency (1.05 MHz) ranging signal; and a receiver sampled the received signal at a 3.2-MHz sampling rate to estimate the time of arrival of the ranging signal. This configuration and an additional protocol supporting bidirectional ranging achieved a 140-mm resolution (equivalent to 2.15 GHz sampling). This method does not modify the PHY but only changes the baseband signal processing. The validity of this method was demonstrated using computer simulation and prototype experiments.