This paper presents an even harmonic quadrature mixer (EH-QMIX) with a simple filter configuration and an integrated LTCC module including LNAs, band rejection filters (BRFs), and the proposed EH-QMIX for W-CDMA direct conversion receiver (DCR). Since the DCR has no spurious responses, a BRF instead of a high-Q band pass filter can be applicable for eliminating undesired signals and it can be built in the LTCC substrates easily. As LO frequency is half of RF frequency in the EH-QMIX, diplexer can be composed of simple filters and it can be also integrated in the substrates. As a result, the whole RF circuits of the EH-DCR using a proposed EH-QMIX are integrated in the LTCC module and miniaturization of the receiver is achieved. Moreover, in order to suppress the degradation of the amplitude and the phase imbalances in the quadrature mixer caused by interferences of signals, RF characteristics of the circuits in the mixer such as reflection coefficients, isolations are discussed. A developed LTCC module shows good performances for W-CDMA direct conversion receiver.

This paper studies the robustness of message masking communication over noisy channels using modified chaotic systems. First, the modified chaotic systems are introduced with a higher capability of transmitting messages than typical chaotic systems. Then, assuming an ideal channel, the chaotic message masking scheme is derived which achieves asymptotic convergence or dead-beat performance for recovering messages. Next, considering the case of noisy channels, an H∞ performance and an L2-gain optimal noise rejection are achieved by solving linear matrix inequality (LMI) problems. Furthermore, the ultimate bound of synchronization error and recovered message error can be adjusted by both design gains and the system parameter of the modified chaos. Using the proposed method, the bit-error-ratio and noise tolerance are improved. Finally, numerical simulations and DSP experiments are carried out to verify the theoretical derivations.

The generalized sorting problem is to find the first k largest elements among n input elements and to report them in a sorted order. In this paper, we propose a fast generalized sorting algorithm under the single hop wireless networks model with collision detection (WNCD). The algorithm is based on the maximum finding algorithm and the sorting algorithm. The key point of our algorithm is to use successful broadcasts to build broadcasting layers logically and then to distribute the data elements into those logic layers properly. Thus, the number of broadcast conflicts is reduced. We prove that the average time complexity required for our generalized sorting algorithm is Θ(k + log(n - k)). When k = 1, our generalized sorting algorithm does the work of finding maximum, and when k = n, it does the work of sorting. Thus, the analysis of our algorithm builds a connection between the two extremely special cases which are maximum finding and sorting.

Genetic Algorithm (GA) and other Evolutionary Algorithms (EAs) have been successfully applied to solve constrained minimum spanning tree (MST) problems of the communication network design and also have been used extensively in a wide variety of communication network design problems. Choosing an appropriate representation of candidate solutions to the problem is the essential issue for applying GAs to solve real world network design problems, since the encoding and the interaction of the encoding with the crossover and mutation operators have strongly influence on the success of GAs. In this paper, we investigate a new encoding crossover and mutation operators on the performance of GAs to design of minimum spanning tree problem. Based on the performance analysis of these encoding methods in GAs, we improve predecessor-based encoding, in which initialization depends on an underlying random spanning-tree algorithm. The proposed crossover and mutation operators offer locality, heritability, and computational efficiency. We compare with the approach to others that encode candidate spanning trees via the Pr?fer number-based encoding, edge set-based encoding, and demonstrate better results on larger instances for the communication spanning tree design problems.

We theoretically analyze the performance of coherent ultrashort light pulse code-division multiple-access (CDMA) communication systems with a nonlinear optical thresholder. The coherent ultrashort light pulse CDMA is a promising system for an optical local area network (LAN) due to its advantages of asynchronous transmission, high information security, multiple access capability, and optical processing. The nonlinear optical thresholder is based on frequency chirping induced by self-phase modulation (SPM) in optical fiber, and discriminates an ultrashort pulse from multiple access interference (MAI) with picosecond duration. The numerical results show that the thermal noise caused in a photodetector dominates the bit error rate (BER). BER decreases as the fiber length in the nonlinear thresholder and the photocurrent difference in the photodetector increase. Using the nonlinear optical thresholder allows for the response time of the photodetector to be at least 100 times the duration of the ultrashort pulses. We also show that the optimum cut-off frequency at the nonlinear thresholder to achieve the minimum BER increases with fiber length, the total number of users, and the load resistance in the photodetector.

In this paper, we propose a novel peak-to-average power ratio (PAPR) reduction method for multi-rate orthogonal frequency division multiplexing (OFCDM) based on an orthogonal variable spreading factor (OVSF) code. In the method, the base station assigns two signs of code sequence to each user to maintain the orthogonality among the code sequences that have different lengths. After that, one sign of the code sequence is selected for reducing the PAPR of the OFCDM symbol. Based on theoretical analysis and computer simulation, we show that the proposed method reduces the PAPR for two data rate classes.

The Japan Aerospace Exploration Agency (JAXA) plans to launch a geostationary satellite called Engineering Test Satellite VIII (ETS-VIII) in FY 2006. In this paper, a microstrip line array antenna, which has a very simple structure, is introduced to radiate a circularly polarized wave aiming at ETS-VIII applications. This antenna consists of a triangular conducting line with its vertexes rounded off, located above a ground plane, with a gap on one of its side to produce a circular polarization. The proposed antenna is analyzed by numerical simulations for a single element as well as for a three elements array configuration and the possibility of beam-switching in the azimuth space is experimentally confirmed in the latter case. It is found that by properly feeding the elements constituting the array antenna, for an elevation angle El = 48in Tokyo area, three beams are created in the conical-cut direction with a minimum gain more than 6.6 dBic and an axial ratio less than 3 dB.

Stratospheric platforms have been recently proposed as a new wireless infrastructure for realizing the next generation of communication systems. To provide high quality services, an investigation of the wireless stratospheric platform channel is essential. This paper proposes a definition and describes an analysis of the wireless channel for the link between stratospheric platforms and terrestrial mobile users based on an experiment in a semi-urban environment. Narrowband channel characteristics are presented in terms of Ricean factor (K factor) and local mean received power over a wide range of elevation angles ranging from 10to 90. Finally, we evaluated average bit error probability based on the proposed channel model to examine the channel performance. For the environment in which the measurements were conducted, we find that elevation angles greater than 40yield better performance.

Scaling of CMOS Integrated Circuit is becoming difficult, due mainly to rapid increase in power dissipation. How will the semiconductor technology and industry develop? This paper discusses challenges and opportunities in system LSI from three levels of perspectives: transistor level (physics), IC level (electronics), and business level (economics).

A novel class of microstrip bandpass filter is configured using the impedance transformers and an improved stepped impedance resonator (SIR). This SIR is composed of a central narrow strip section with an aperture on ground and two wide strip sections at the two sides. This low-high-low SIR resonator has a promising capability in achieving an extremely large ratio of first two resonant frequencies for design of a bandpass filter with ultra-broad stopband. The two quarter-wavelength transformers with low and high impedances, referred as to impedance- and admittance-inverters, are modeled and utilized as alternative types of inductive and capacitive coupling elements with highly tightened degrees for wideband filter design. After extensive investigation is made on the two transformers and the proposed SIR, the two novel bandpass filters are constructed, designed and implemented. Two sets of predicted and measured frequency responses over a wide frequency range both quantitatively exhibit their several attractive features, such as ultra-broad stopband with deep rejection and broadened dominant passband with low insertion loss.

We have clarified both theoretically and experimentally the basic performance of distributed Raman amplification (DRA) transmission systems in trunk networks with DSF or SMF spans with limited pump power where the pump power is limited by practical considerations. The gain and noise characteristics of a fiber span with splice loss are accurately determined by employing three approximation models. A novel pumping scheme called band enhanced pumping (BEP) is proposed that improves the DRA gain and optical SNR (OSNR) by 1.5 and 0.55 dB, respectively, compared with those of a conventional pumping scheme, under typical system conditions. We show that a DRA system with a DSF span has OSNRs that are 2.1 and 2.9 dB higher than those of a system with an SMF span at limited pump powers of 200 and 400 mW, respectively, as typical examples.

We consider oscillators consisting of a reactance circuit and a negative resistor. They may happen to have multi-mode oscillations around the anti-resonant frequencies of the reactance circuit. This kind of oscillators can be easily synthesized by setting the resonant and anti-resonant frequencies of the reactance circuits. However, it is not easy to analyze the oscillation phenomena, because they have multiple oscillations whose oscillations depend on the initial guesses. In this paper, we propose a Spice-oriented solution algorithm combining the harmonic balance method with Newton homotopy method that can find out the multiple solutions on the homotopy paths. In our analysis, the determining equations from the harmonic balance method are given by modified equivalent circuit models of "DC," "Cosine" and "Sine" circuits. The modified circuits can be solved by a simulator STC (solution curve tracing circuit), where the multiple oscillations are found by the transient analysis of Spice. Thus, we need not to derive the troublesome circuit equations, nor the mathematical transformations to get the determining equations. It makes the solution algorithms much simpler.

We propose a new receiving method for an information-providing system that uses LED-based traffic lights as the transmitter. We analyzed the improvements obtained when 2-dimentional image sensor replaced the conventional single-element photodiode. First, we discuss the maximum receiver's field of view (FOV) when using the 2-dimentional image sensor at a particular focal length. We analyzed the best vertical inclination for both lanes and quantified the improvements in terms of the enhancement of received signal-noise ratio (SNR) when different numbers of pixels were applied. Our results indicate that using more pixels increases the received SNR and the service area becomes wider compared to the conventional single-element system. Consequently, receivable information within the service area also increased. We also found that the optimum number of pixels to accomplish a reliable communication system is 5050 because performance degradation occured with a larger number of pixels.

A novel error detection method based on coded block pattern (CBP) information verification is proposed for error concealment of inter-coded video frames transmitted in wireless channel. This method firstly modifies the original video stream structure by the aggregation of certain important information, and then inserts some error verification bits into the video stream for each encoded macro block (MB), these bits can be used as reference information to determine whether each encoded MB is corrupted. Experimental results on additive Gauss white noise simulation wireless channel and H.263+ baseline codec show that the proposed method can outperform other reference approaches on error detection performance. In addition, it can preserve the original video quality with a small coding overhead increase.

In this paper, routing properties of cube-based optoelectronic OTIS networks are explored. We show emulations of various cubical network topologies on their OTIS augmented variants, including the n-D grid networks, shuffle-exchange, and de Brujin networks. An analytical performance model for OTIS-cube networks is proposed. The model is validated by means of comparison with rigorously obtained simulation results. Using this model, the performance characteristics of the OTIS-hypercube network are evaluated in view of a number of different constraints. Moreover, we compare the performance characteristics of the OTIS-hypercube with that of equivalent fully-electronic networks under various implementation constraints.

The 5-cm-diameter double-sided YBa2Cu3O7 (YBCO) films were prepared by metal organic deposition (MOD) using a commercially available metal-naphthenate coating solution. Firstly, YBCO film was prepared by MOD on one side of a double-side-polished 5-cm-diameter LaAlO3 substrate. Secondly, another side was similarly coated with YBCO by MOD. After the latter processing, degradation of average Jc value in the first side was not observed; but the fluctuation of critical current density Jc slightly increased. The double-sided YBCO films showed average Jc values of 0.8-1.0 MA/cm2 at 77 K and microwave surface resistances Rs(12 GHz) of 0.86-1.07 mΩ at 70 K.

A novel low-voltage low-distortion analog sampling switch is proposed in this letter. A "source tracker" techniuqe is used to distinguish the real source terminal of the sampling switch. The turn-on resistance of the sampling switch is kept exactly constant. The modified switch makes the rail-to-rail input signal swing possible for low voltage. TSMC 0.18 µm standard CMOS technology is utilized in this research. Results indicate that much lower Total Harmonic Distortion (THD) is achieved by the proposed circuit. The low THD meets the requirements in the application of the low-voltage low-distortion switched-capacitor circuits.

The performance of parallel computing applications is highly dependent on the efficiency of the underlying communication operations. While often characterized as dynamic, these communication operations frequently exhibit spatial and temporal locality as well as regularity in structure. These characteristics can be exploited to improve communication performance if the correct prediction model is selected to a suitable communication topology. In this paper we describe an entropy based methodology for quantifying and evaluating the success of different prediction models on actual workloads drawn from representative parallel benchmarks. We evaluate two different prediction criteria and combinations thereof: (1) Messages are partitioned by source node. (2) Use of a first order context model. We also describe the threshold for predication designed to largely avoid incorrect predication overheads. Our results show for simple predication models, even on highly dynamic benchmark applications, predictability can be improved by several orders of magnitude. In fact, using simple prediction techniques, over 75% of the communication volume is accurately predictable.

A new seamless symbol rate switchable modem for multi-rate FDMA systems is proposed in this paper. In the new modem, a novel clock phase compensation algorithm makes it possible to switch the symbol rate synchronously between the transmitter and the receiver, with no degradation in BER when the symbol rate is changed. In addition, by matching the interpolation filter to the symbol rate, this modem is capable of operating at lower clock speeds, which greatly reduces the consumption power. Computer simulations confirm its fundamental performance. Simulation results show that the proposed power-efficient symbol rate switchable modem can change the symbol rate without degrading BER performance.

This paper describes a high-speed MT connector assembly method. This technique uses adhesive with a short hardening time, is highly reliable and does not require a polishing process, thus reducing the connector assembly time. First, we investigated an alpha-cyanoacrylate adhesive that hardens quickly and whose adhesive strength does not decrease under high humidity and high temperature conditions, thus ensuring its excellent reliability for outside use. In addition, we investigated variations in the position of the fiber endface on the ferrule endface with a view to obtaining a low insertion loss. Based on the results, we assembled an MT connector using our proposed high-speed assembly method. We confirmed that the assembly time could be reduced to less than 70% of the time required with the conventional method. MT connectors assembled using this technique have a low insertion loss and stable environmental characteristics.