To create a next-generation mobile satellite communication system that offers large communication capacity, the onboard antenna system must be a multi-beam system consisting of a light weight 20-m class reflector and a light weight 100-beam class antenna feed system. We clarify that the antenna gain decrease created by the reflector surface distortion expected in orbit is relatively large. This paper presents a deformed antenna pattern compensation method that minimizes circuit scale. Validity of the proposed method is confirmed by antenna pattern calculations and experiments on a fabricated array-fed reflector antenna.

We present a linear-time algorithm for treating collision response of articulated rigid bodies in physically based modeling. By utilizing the topology of articulated rigid bodies and the property of linear equations, our method can solve in linear time the system of linear equations that is crucial for treating collision response.

In this paper, small sized arrays with a few elements are investigated. The antenna diameter is assumed to be less than 3λo. The focus of this paper is to compare the gain characteristics of a triangle arrangement with these of a uniform arrangement. The method of moments is used to calculating the gain characteristics. It is shown that the triangle arrangement is not always sufficient to obtain maximum gain for a small-sized antenna with only a few elements. Also, the type of antenna element used greatly influences the required number of elements and the element configuration.

In Optical Burst Switched (OBS) networks, packets are assembled into bursts at ingress edge routers and disassembled at egress edge routers. This letter presents an analytical model to quantify the burstification latency in the OBS networks. To the authors' best knowledge, this letter is the first one to address the latency issue in OBS in a comprehensive manner analytically. The results allow us to quantitatively understand how OBS network parameters such as maximum burst length and maximum timeout affect the packet latency in the OBS networks. We show that the burstification latency in the OBS network is bounded and can be tuned by setting the system parameters under latency constraints.

A double square loop antenna with fractal geometry that supports for multiband operation is proposed. The antenna has multiband operation in that the generator model, which is an initial model to create a fractal loop antenna to operate at the first and second resonant frequencies, is inserted at each center side of a big square loop antenna. It also has a small square loop to operate at the third resonant frequency. The proposed antenna is implemented and shown to effectively support the global system for mobile communication (880-960 MHz), digital communication system (1710-1880 MHz), personal communication system (1850-1990 MHz), universal mobile telecommunication system (1920-2170 MHz), and wireless local area network (2400-2483 MHz) bands. The radiation patterns of the proposed antenna are still similar to a bidirectional radiation pattern. The properties of the antenna such as return losses, radiation patterns and gain are determined via numerical simulation and measurement.

In this paper, we report the detailed investigation of novel printed disc monopole antennas for ultra-wideband (UWB) applications focusing on miniaturization of the disc radiator. First, the basic property was examined for the case of a circular disc with diameter of 50 mm, and it was found that the VSWR is less than 2 in the UWB band of 3.1-10.6 GHz when the feed gap length is between about -0.1 and 0.2 mm. Next, in order to reduce the size of the disc radiator, various dimensions of elliptical discs were investigated. It is shown that if the dimensions of the elliptical disc are chosen appropriately, a smaller disc size antenna can be achieved. To decrease the antenna size further, a triangular notch and an exponentially curved notch on the ground plane of the antenna were examined. It is observed that the use of the notched ground is very effective and that the diameter of the circular radiator can be reduced to 17 mm. The proposed antenna has an omnidirectional pattern in the x-y plane. The influence of the notch on the radiation pattern is very small. Details of the simulation results using the FDTD method and experimental results for the proposed antenna are presented and analyzed. These features are very attractive for UWB applications.

This paper describes a beam scanning antenna that consists of a movable dielectric plate loaded onto a microstrip comb-line antenna. This type of antenna uses a mechanical system and so offers a simple structure and low cost. The main beam direction of the proposed antenna is changed by moving the dielectric plate. The guide wavelength of the microstrip line was measured at the quasi-millimeter wave band (20 GHz) when moving the dielectric plate to investigate the possibility of beam scanning. The proposed antenna was fabricated to experimentally demonstrate its principle operation. A possible beam scanning angle of 20 degrees was confirmed.

An experimental study concerning Ultra Wideband (UWB) Microwave Radar for breast cancer detection is described. A simple phantom, consisting of a cylindrical plastic container with a low dielectric constant material imitating fatty tissues and a high dielectric constant object emulating tumour, is scanned with a tapered slot antenna operating between 3.1 to 10.6 GHz. A successful detection of a target is accomplished by a visual inspection of a two-dimensional image of the scanned phantom

Basic microwave properties of magnetic photonic (MPC) and degenerate band edge (DBE) crystals are investigated mathematically and experimentally. Two dimensional and three dimensional models are considered demonstrating the very high sensitivity and field growth associated with these crystals. A major part of the paper deals with the development of realistic anisotropic periodic structures using a combination of layers constructed from thin film frequency selective surfaces, alumina, titanate and calcium vanadium garnet (CVG) materials. Measurements for antenna applications demonstrate and validate the theoretical performance of the MPC and DBE crystals. The latter part of the paper will present an exciting and promising development relating to microwave circuit applications. Specifically, a novel dual-line printed circuit is presented to emulate propagation in anisotropic media. As such, the MPC and DBE phenomena can be realized using very simple printed circuits (coupled lines). Lastly, physically small printed antennas and arrays based on the coupled transmission lines are presented.

This paper reviews our recent antennas and propagation studies for MIMO systems. First we introduce a MIMO propagation channel model in which an interesting nature can be found in eigenvalue statistics from a practical viewpoint. Then we introduce multi-keyhole model which is an efficient tool for designing a MIMO repeater systems, or MIMO radio-relay systems. For realization of compact MIMO antenna systems, effectiveness of using multiple polarizations such as dual polarizations and triple polarizations is demonstrated in multipath-rich propagation environments. With application of MIMO to OFDM systems, we focus our analysis on relation between propagation and digital transmission characteristics under a severe multipath-rich environment where the delay profile exceeds the guard interval. Finally, we discuss transmission characteristics of MIMO-OFDM with maximal ratio combining (MRC) diversity in the environment.

High-resolution Direction-of-Arrival (DOA) estimation techniques for antenna arrays have been widely desired in many applications such as smart antennas, RF position location, and RFID system. To realize high-resolution capability of the techniques, precise array calibration is necessary. For an array of single-mode elements, a calibration matrix derived by the open-circuit method is the simplest one. Unfortunately, calibration performance of the method is not enough for the high-reslution DOA estimation techniques. In this paper, we consider problems of the calibration matrix derived by the method, and show that errors in the matrix can be effectively removed by an optimal diagonal weight coefficient. In the proposed compensation technique, the number of newly introduced parameters, or unknowns, is only one for an array of the identical elements. Performance of the simple compensation technique is verified numerically and experimentally.

This paper describes a method for evaluating the performance of a small magnetic core loop antenna used for radio controlled watches. Recently, amorphous metal core loop antennas are used as built-in small antennas inside a metal case. It is difficult to perform electromagnetic simulation for amorphous core loop antennas because of the complicated laminate structure. Therefore, we modeled the amorphous metal core loop antenna as an equivalent bulk structure having anisotropic permeability property that we can simulate. We analyzed the receiving sensitivity of the amorphous antenna by calculating the antenna factor. The receiving sensitivity degrades remarkably when an antenna is inside a metal case. We performed further simulation to investigate eddy current losses that cause deterioration.

This paper presents a novel dual-band comb-line filter using a pair of hybrid resonators. The resonator consists of a half-wavelength stripline resonator short-circuited at both ends and a quarter-wavelength resonator of coplanar waveguide that is nested in the half-wavelength resonator. Numerical calculations by an electromagnetic simulator clarify the characteristics of dual-frequency resonance of the hybrid resonator when the structural parameters are changed. The surface current density on the resonator is also investigated at the resonant frequencies. A typical model of the resonator is fabricated and its resonance frequency characteristics are measured.

This letter proposes a sliding window method with iterative tuning for channel estimation of UWB signals. The iterative tuning scheme, which is based on multiple iterations of least mean square (LMS) algorithm, is utilized for modifying the output of the conventional sliding window channel estimator. By using this, the proposed method is more flexible due to the tradeoff between the processing time and accuracy, which makes it more suitable for practical UWB wireless communications. Simulations are also provided for demonstrating the validation of the proposed method.

IP (Intellectual Property) reuse plays an important role in modern IC design so that IP Protection (IPP) technique is get concerned. In this paper, we introduce a new efficient watermarking system for IPP on post-layout design stage. The signature (which indicates the designer) is encrypted with a secret key by DES (Data Encryption Standard) to produce a bit string, which is then embedded into the layout design as constraints by using a specific incremental router. Once the design is watermarked successfully, the signature can be extracted accurately by the system. The system also has a strong resistance to the attack on watermarking due to the DES functionality. This watermarking technique uniquely identifies the circuit origin, yet is difficult to be detected or fabricated without our tool. We evaluated the watermarking system on IBM-PLACE 2.0 benchmark suites. The results show the system robustness and strength: the system success probability achieves 100% in suitable time with no extra area and wire length cost on design performances.

This paper presents the switched-beam slot antenna over the electromagnetic band-gap (EBG) reflector. This antenna is composed of two slot elements fed with a phase difference and the EBG reflector, which is used in order to realize a low profile structure. The radiation characteristics of this antenna are calculated using the FDTD method. Calculations show that the height of the antenna using the EBG reflector is 60 % lower than that of the antenna using a perfect electric conductor (PEC) reflector. The radiation characteristics at the center of the operating frequency band in the EBG reflector are equivalent to that in the PEC reflector. It is shown that the tilt angle of the main beam in the elevation plane varies with the operating frequency, and the variation in the case of the EBG reflector is caused by its frequency-dependent reflection phase. Moreover, the radiation pattern of the fabricated antenna is measured. The results demonstrate that the low profile design can be achieved by using the EBG reflector, and reveal the influence of the EBG reflector on the antenna efficiency.

Leaky wave radiation from evanescent-mode left-handed (LH) transmission lines is investigated that are composed of a cut-off parallel plate waveguide loaded with a one-dimensional (1-D) array of the disc type dielectric resonators. The apertures are placed on side walls of the parallel plate waveguide. First of all, the dispersion diagram is numerically obtained with the complex eigenmode solutions. The simulated and measured backward wave radiation characteristics validate the backward wave propagation along the 1-D waveguides. Based on the concept, the backfire leaky wave antenna was designed and demonstrated with the 15-cell structure. The beam scanning with the operational frequency was achieved by more than 30 degrees.

Behavioral synthesis, which automatically synthesizes an RTL circuit from a sequential program, is one of promising technologies to improve the design productivity. This paper proposes a function call optimization method in behavioral synthesis from large sequential programs with a number of functions. We formulate the optimization problem using integer linear programming. Our experimental results show the reduction in the circuit area by up to 44.6%, compared with a traditional method.

In orthogonal frequency-division multiplex access (OFDMA) downlink systems, the carrier-frequency offset (CFO) between the multiple transceivers introduces inter-carrier interference (ICI). In this letter, we propose an iterative precoding scheme to suppress the ICI due to CFO. This scheme is applied at the transmitter, and can jointly cancel the ICI for all the receivers. Moreover, by the studies of the convergence behavior of the iterations, a sufficient condition for the convergence is presented. The theoretical analysis and simulation results both show that this iterative scheme is equivalent to the zero-forcing (ZF) scheme in function, but with much lower complexity.

Due to the limited resources of sensor nodes, an energy-efficient routing algorithm of Wireless Sensor Networks is considered as one of the most important issues in improving network lifetime. To resolve this issue, several routing algorithms have been suggested, but the published studies have mainly focused on minimizing distances between sensor nodes or the number of hops. These researches have also assumed that all the sensor nodes participate in the sensing task. In this paper, we propose a new cluster head selection algorithm focusing on both the density of sensor nodes and sensing-awareness that has not been considered yet in other existing researches on cluster-based routing scheme. In the real sensor network environment, only a part of sensor nodes participates in data reporting, so consideration of sensing-awareness in a routing algorithm will have effect on network efficiency. Moreover, the density of sensor nodes that has resulted from geographical location of sensor nodes can be an important factor in cluster head selection. The simulation results show that the proposed algorithm, by considering these 2 factors simultaneously, reduces energy consumption and enhances network lifetime.