A new type of edge-guided mode (E. G. Mode) isolator is proposed, which has the following desirable characteristics: (a) high isolation (more than 40 dB with 1dB insertion loss), (b) simple structure without additional lossy materials, and (c) considerably broad band (40% relative bandwidth). Moreover, a new type of E. G. mode circulator for which the scattering matrix is of the non-cyclic from is also proposed.

MIMO two-way multi-hop networks are considered in which the radio resource is fully reused in all multi-hop links to increase spectrum efficiency while the adjacent interference signals are cancelled by MIMO processing. In addition, the nodes in the multi-hop network optimize their transmit powers to mitigate the remaining overreach interference. Our main contribution in this paper is to investigate an efficient relay placement method with power allocation in such networks. We present two formulations, namely QoS-constrained optimization and SINR balancing, and solve them using a sequential geometric programming method. The proposed algorithm takes advantage of convex optimization to find an efficient configuration. Simulation results show that relay placement has an important impact on the effectiveness of power allocation to mitigate the interference. Particularly, we found that an uniform relay location is optimal only in power-limited scenarios. With optimal relay locations, significant end-to-end rate gain and power consumption reduction are achieved by SINR balancing and QoS-constrained optimization, respectively. Furthermore, the optimal number of hops is investigated in power or interference-limited scenarios.

The arithmetic operations over the finite field GF(pn) has many important applications. There is a need for a fast inverter circuit over the finite field GF(pn), because inversion' is must complicated and lengthy operation. In this paper, we will propose a design method of fast inverter circuit that is based on Euclid's algorithm. The inverter circuit is composed of a number of identical basic circuits. Therefore the designed circuit has a regular and expandable feature and has a modular structure.

An equivalent circuit of a circular patch array absorber has been proposed, however the method to identify a winding ratio of a transformer in its circuit have never been reported. In this paper, it is indicated that the ratio is proportionate to the area ratio between patch and unit cell of the absorber, and the design method of the winding ratio is proposed. The winding ratio derived by the proposed method is agreed well with that by using electromagnetic simulator within 3% error. Moreover, the operating frequency and 15 dB bandwidth of the fabricated absorber designed by proposed method are agreed with those derived by the circuit simulation within 0.4% and 0.1% errors. Thus the validity of the proposed method is verified.

In this paper, we show a collusion attack on the novel and sophisticated ID-based non-interactive key sharing scheme proposed by Tanaka [2], [3]. It is based on a linear algebraic approach [4]. We discuss its complexity and provide numerical simulation results of the success probability in forging the shared keys.

It is known that demand and supply power balancing is an essential method to operate power delivery system and prevent blackouts caused by power shortage. In this paper, we focus on the implementation of demand response strategy to save power during peak hours by using Smart Grid. It is obviously impractical with centralized power control network to realize the real-time control performance, where a single central controller measures the huge metering data and sends control command back to all customers. For that purpose, we propose a new architecture of hierarchical distributed power control network which is scalable regardless of the network size. The sub-controllers are introduced to partition the large system into smaller distributed clusters where low-latency local feedback power control loops are conducted to guarantee control stability. Furthermore, sub-controllers are stacked up in an hierarchical manner such that data are fed back layer-by-layer in the inbound while in the outbound control responses are decentralized in each local sub-controller for realizing the global objectives. Numerical simulations in a realistic scenario of up to 5000 consumers show the effectiveness of the proposed scheme to achieve a desired 10% peak power saving by using off-the-shelf wireless devices with IEEE802.15.4g standard. In addition, a small-scale power control system for green building test-bed is implemented to demonstrate the potential use of the proposed scheme for power saving in real life.

In this paper, three new ultra wideband (UWB) communication systems with quadrature-phase shift keying (QPSK) impulse modulation are proposed. First, direct-sequence (DS) multiple-access scheme is applied. The second proposed system is based on time-hopping (TH) multiple-access scheme. The last proposed system applies TH multiple-access scheme with QPSK impulse modulation and pulse position modulation (PPM). The conventional UWB communications as TH scheme with PPM modulation and DS scheme with binary-phase shift keying (BPSK) are used to compare. The simulation results show that all proposed UWB communication systems can provide obviously better performances compared with the conventional TH-PPM and DS-BPSK UWB communication systems. The comparisons in aspects of transmission bit rate and the number of users are also investigated.

To reduce laborious tasks of the phase determination, our previous paper has proposed a method to derive phase reference for two-tone intermodulation distortion (IMD) measurement of a power amplifier (PA) by using small-signal S-parameters. Since the method is applicable to low output power level, this paper proposes an iterative process to extend the applicable power level up to 1-dB compression. The iterative process is based on extraction of linear response: the principle of the extraction is described theoretically by using an accurate model of the PA with memory effect. Measurement of two-tone IMD is made for a GaN FET PA. Validity of the iteration is confirmed as convergence of the extracted linear response to that given by the product of S21 and input signal. Measured results also show validity of the physical model of the memory effect provided by Vuolevi et al. because beat frequency dependences of IMD's are accurately fitted by bias impedances at even order harmonics of envelope frequency. The PA is characterized by using measured results and the third and fifth order inverses of the PA are designed. Improvement of IMD is theoretically confirmed by using the inverses as predistorters.

This paper reports the prehistory of software defined radio (SDR) studies in Japan. In 1999, a boom in the field of SDR started in Japan, and this year an ARIB study group completed its final report on SDR. SDR is a recently proposed technology concept and has attracted the attention of many communication engineering researchers. SDR will become one of the most important technologies in advanced communication, broadcasting and intelligent transportation systems on the 21st century. Although SDR has several attractive features, there are also many design issues to be solved. In this work we have examined these issues and discussed a new design methodology for wireless receivers in the SDR era.

It is expected that software receivers will be widely available for radio communication, broadcasting and radio monitoring applications because they are able to be equipped with multimode, multirate and multiband functions in a single hardware platform. This paper describes the basic techniques required for software receivers for both hardware and software. The evaluation items and methods were studied and some evaluations done with an experimental software receiver model fabricated for radio monitoring applications. Future concepts in radio communication, broadcasting and radio monitoring applications where software receivers are thought to be suitable, were studied, and problems for realization identified.

An optimization of the smoothing preprocessing for the correlated signal parameter estimation was considered. Although the smoothing factor (the number of subarrays) is a free parameter in the smoothing preprocessing, a useful strategy to determine it has not yet been established. In this paper, we investigated thoroughly about the smoothing factor and also proposed a new scheme to optimize it. The proposed method, using the smoothed equivalent diversity profile (SED profile), is able to evaluate the effect of smoothing preprocessing without any a priori information. Therefore, this method is applicable in the real multipath parameter estimation.

This paper proposes a new methodology to design optimal antennas for MIMO (Multi-Input Multi-Output) communication systems by using spherical mode expansion. Given spatial channel properties of a MIMO channel, such as the angular profile at both sides, the optimal MIMO antennas should provide the largest channel capacity with a constraint of the limited implementation space (volume). In designing a conventional MIMO antenna, first the antenna structure (current distribution) is determined, second antenna directivity is calculated based on the current distribution, and thirdly MIMO channel capacity is calculated by using given angular profiles and obtained antenna directivity. This process is repeated by adjusting the antenna structure until the performance satisfies a predefined threshold. To the contrary, this paper solves the optimization problem analytically and finally gives near optimal antenna structure (current distribution) without any greedy search. In the proposed process, first the optimal directivity of MIMO antennas is derived by applying spherical mode expansion to the angular profiles, and second a far-near field conversion is applied on the derived optimal directivity to achieve near optimal current distributions on a limited surface. The effectiveness of the proposed design methodology is validated via numerical calculation of MIMO channel capacity as in the conventional design method while giving near optimal current distribution with constraint of an antenna structure derived from proposed methodology.

In this paper, two new modulation schemes, Multi-Pulse Modulation (MPM) and Differential Multi-Pulse Modulation (DMPM) have been proposed in order to increase the total data rate and improve the error performance. By these schemes, the modulated pulse that had been used for transmitting only one data bit in each pulse-pair in conventional TR-UWB system, can be used for transmitting more than one bit data depending on the level of modulation. Moreover, the error performance has been improved by these new modulation schemes because for the same Eb/N0, the energy per pulse has increased. In addition, these new modulation schemes are applied to a multiple access system. The simulation results show that the total throughput performance of the proposed system has been improved, nearly 2-4 times when compared to the conventional TR-UWB communication system.

This paper presents the performance of the Directionally Constrained Minimization of Power (DCMP) and the Zero-Forcing (ZF) in the Angular Spread (AS) environment. To obtain the optimal weights for both methods, the Extended Array Mode Vector (EAMV) is employed. It is known that the EAMV represents the instantaneous AS as well as the instantaneous DOA in the slow fading channel. As a result, it is shown that the DCMP and the ZF using the EAMV estimates can improve the Signal-to-Interference-plus-Noise Ratio (SINR) considerably, as compared with those using the Direction of Arrival (DOA) information only. At the same time, the intrinsic problems causing the performance loss in the DCMP and the ZF are revisited. From this, the reasons for the performance deterioration are analyzed, in relation with the AS, the number of samples, the number of antenna elements, and the spatial correlation coefficient of the signals. It follows that the optimal signal combining techniques using the EAMV estimates can diminish such effects.

Multi-Input Multi-Output (MIMO) systems, which utilize multiple antennas at both the receiver and transmitter, promise very high data rates in a rich scattering environment. It was proven in literature that with optimal power allocation, MIMO eigenmode transmission system (EMTS) is optimal because MIMO capacity is maximized. However, the performance of MIMO EMTS is very sensitive to the accuracy of channel state information and thus it is of practical importance to analyze its performance when channel state information is corrupted under realistic system and propagation conditions. In this paper, we lower bound the mutual information of MIMO EMTS with imperfect channel estimation and delayed quantized feedback in a spatially correlated continuous fading channel. Our results showed that this lower bound is tight and can serve as a comprehensive guide to the actual performance of MIMO EMTS under practical operating conditions.

The paper describes a low complexity tree-structure based user scheduling algorithm in an up-link transmission of MLD-based multi-user multiple-input multiple-output (MIMO) wireless systems. An M-branch selection algorithm, which selects M most-possible best branches at each step, is proposed to maximize the whole system sum-rate capacity. To achieve the maximum capacity in multi-user MIMO systems, antennas configuration and user selection are preformed simultaneously. Then according to the selected number of antennas for each user, different transmission schemes are also adopted. Both the theoretical analysis and simulation results show that the proposed algorithms obtain near optimal performance with far low complexity than the full search procedure.

MIMO (Multiple Input Multiple Output) communications systems equipped with array antennas at both the transmitter and receiver sides are a promising scheme to realize higher rate and/or reliable data transmission. In this paper, capacity analysis of MIMO Rayleigh channel with spatial correlation at the receiver of multipath taken into account is presented. In general, a model configuration of local scattering around a mobile station in MIMO environment is carried out by simulation to examine spatial correlation coefficients. Based on statistical properties of the eigenvalues of correlated complex random Wishart matrices, the exact closed-form expressions of distribution of the eigenvalues are investigated. Then, the general closed-form evaluation of integral form is proposed based on Meijer's G-function. The results demonstrate that the ergodic capacities are improved by increasing the number of the antennas and the SNR's. Compared with i.i.d. (independent identically distributed) Rayleigh channel, the incremental improvement of correlated Rayleigh channel is reduced by spatial fading correlation. The analytical results validated by Monte-Carlo simulations show a good agreement.

A detailed analysis of a multilayer symmetric coupler employing symmetrical broad-side coupled lines is presented. We confirm that the coupler can be designed using a well-known even-odd mode analysis of two strip lines while the coupler has four strip lines. We also confirm that the previously reported poor isolation originates from port mismatching. To verify the analysis, couplers that have different dimensions are fabricated. One example exhibits a coupling loss of 4.50.5 dB, a return loss better than 15 dB, and isolation characteristics higher than 12 dB in the 6.5 to 15.1 GHz frequency range. These results agree well with the obtained simulation results. The results show that the coupler has the potential to provide tight and ideal coupling.

Recently, wireless multi-hop network using MIMO two-way relaying technique has been attracted much attention owing to its high network efficiency. It is well known that the MIMO two-way multi-hop network (MTMN) can provide its maximum throughput in uniform topology of node location. However, in realistic environments with non-uniform topology, network capacity degrades severely due to unequal link quality. Furthermore, the end-to-end capacity also degrades at high SNR due to far (overreach) interference existing in multi-hop relay scenarios. In this paper, we focus on several power allocation schemes to improve the end-to-end capacity performance of MTMN with non-uniform topology and far interference. Three conventional power allocation schemes are reformulated and applied under the system model of MTMN. The first two are centralized methods, i.e., Eigenvector based Power Allocation (EPA) which employs linear algebra and Optimal Power Allocation (OPA) using convex optimization. The last one is Distributed Power Allocation (DPA) using game theory. It is found from numerical analyses that the power allocation schemes are effective for MTMN in terms of end-to-end capacity improvement, especially in non-uniform node arrangement and at high SNR.