TCP performance in the IEEE 802.11-based multihop ad hoc networks is extremely poor, because the congestion control mechanism of TCP cannot effectively deal with the problem of packet drops caused by mobility and shared channel contention among wireless nodes. In this paper, we present a cross-layer method, which adaptively adjusts the TCP maximum window size according to the number of RTS (Request To Send) retry counts of the MAC layer at the TCP sender, to control the number of TCP packets in the network and thus decrease the channel contention. Our simulation results show that this method can remarkably improve TCP throughput and its stability.

The motion of arc spots of breaking arc is investigated for Ag electrical contacts in DC 42 V/10 A resistive circuit using a high-speed camera. Also, the eroded contact surfaces are observed with a microscope after each breaking operation. As results, some kinds of different films and eroded regions are distinguished. Diameters of these regions are corresponding to the widths of the cathode and anode spot regions that are obtained by using the high-speed camera. It is found that the films and eroded regions on the electrical contacts are generated at different stages of the breaking arc.

The multichannel switch is an architecture widely used for ATM (Asynchronous Transfer Mode). It is known that the fault tolerant characteristic can be incorporated in into the multichannel crossbar switching fabric. For example, if a link belonging to a multichannel group fails, the remaining links can assume responsibility for some of the traffic on the failed link. On the other hand, if a fault occurs in a switching element, it can lead to erroneous routing and sequencing in the multichannel switch. We investigate several fault localization algorithms in multichannel crossbar ATM switches with a view to early fault recovery. The optimal algorithm gives the best performance in terms of time to localization but is computationally complex, which makes it difficult to operate in real time. We develop an online algorithm which is computationally more efficient than the optimal one. We evaluate its performance through simulation. The simulation results show that the performance of the online algorithm is only slightly suboptimal for both random and bursty traffic. There are cases where the proposed online algorithm cannot pinpoint down to a single fault. We explain the causes and enumerate those cases. Finally, a fault recovery algorithm is described which utilizes the information provided by the fault localization algorithm. The fault recovery algorithm adds extra rows and columns to allow cells to detour the faulty element.

A novel millimeter wave quadruple-push oscillator is presented in this paper. The quadruple-push oscillator consists of four identical sub-circuits and a ring resonator that is used as a common resonator. It is well known that there are two orthogonal resonant modes on a one-wavelength ring resonator. According to this resonant characteristic, two orthogonal push-push oscillations can be set up in the quadruple-push oscillator, and there is a phase difference of 90among four sub-circuits due to nonlinear performance. Therefore, the four identical sub-circuits can oscillate at the same fundamental frequency f0, and the fundamental oscillating signal of one sub-circuit has phase differences of 90, 180and 270to that of the others, and the desired fourth harmonic signals can be combined due to their in phase relations, and the undesired fundamental signals, the second harmonic signals, the third harmonic signals and so on can be suppressed when the oscillating signals of the four sub-circuits are added in phase. The principle is firstly explained in this paper, and is proved in the experiment of a Ka-band quadruple-push oscillator. The measured output power of the desired fourth harmonic signal (4f0) was +1.67 dBm at the frequency of 35.8 GHz. The measured suppression of the undesired signals of the fundamental signal (f0), the second harmonic signal (2f0), the third harmonic signal (3f0) and the fifth harmonic signal (5f0) were -18.0 dBc, -17.9 dBc, -17.8 dBc and -35.5 dBc, respectively. The measured phase noise performances at 35.8 GHz were -104.0 dBc/Hz and -82.3 dBc/Hz at the offset frequency of 1 MHz and 100 kHz, respectively.

Since the inception of Globally Asynchronous Locally Synchronous (GALS) VLSI design, GALS has been considered a promising design technique for multi-clock-domain System-on-Chip (SoC). Among the handshake protocols available for SoC design, delay insensitive (DI) handshake protocol is becoming a core technology, since it facilitates robust data transfer regardless of wire delay variation. In this paper, a new data encoding scheme Differential Value Encoding (DVE) is proposed for two-phase 1-of-N DI handshake protocol. Compared with the conventional data encoding method, the proposed scheme effectively reduces the crosstalk effect on wires sending sequentially increasing data patterns, resulting in reduction of the data transfer time. Simulation results with SPEC CPU 2000 benchmarks and sequentially increasing data pattern reveal that the DVE scheme can reduce the crosstalk effect by tens of percentage and significantly decrease the data transfer time.

Crosstalk or coupling phenomenon between two parallel conductors with a ground or reference conductor is well known in electromagnetic compatibility and microwave circuit fields. In this paper we consider the characteristics of a long two-conductor line embedded in an inhomogeneous medium while taking account of the difference between two phase constants in independent propagation modes of two parallel lines. The characteristics of near-end and far-end crosstalk and of through-end transmission are discussed for frequencies up to more than the frequency where the line length is 10 times the wavelength. Interesting properties, such as very strong and null crosstalk phenomena that occur at the far end and non-transmission at the through end, appear in the envelope characteristics. The reason for these properties is clarified by making theoretical and experimental investigations.

A new and simple image processing approach for the measurement of the length of pedestrian crossings with a view to develop a travel aid for the blind people is described. In a crossing, the usual black road surface is painted with constant width periodic white bands. The crossing length is estimated using vector geometry from the left- and the right-border lines, the first-, the second- and the end-edge lines of the crossing region. Image processing techniques are applied on the crossing image to find these lines. Experimental results using real road scenes with pedestrian crossing confirm the effectiveness of the proposed method.

In a partially coupled-line bandpass filter (BPF), a combination of two microstrip line resonators which are partially coupled, are considered, where one resonator is half-wavelength (λ/2)-long, and another whose one end is grounded, is only quarter-wavelength (λ/4)-long. Therefore, the length of a coupled-line section can be varied based on the position of the grounding end, and five conditions of the movable coupling length have been simulated which will greatly influence the spurious responses of a BPF. This property is numerically investigated in this paper. The analysis shows that, based on the grounding position, this method is capable of realizing the improved out-of-band characteristics by locating the multiple attenuation poles in the stopband and improved spurious responses up to five times of the center frequency (5f0). A few empirical models of BPF are fabricated, and the numerical results are ensured by comparing with the experimental results.

Two types of miniaturized high-temperature superconducting filters are described in this paper. The first type is developed by using small-sized microstrip spiral resonators, and the second type by coplanar waveguide quarter-wavelength resonators. The filters have significantly reduced size compared with many previous HTS filters. They are designed by employing an electromagnetic simulator in combination with appropriately chosen equivalent circuits. Their measured frequency responses agree well with theoretical predictions, and show low insertion losses in spite of their small sizes.

In this paper, a pilot-assisted channel estimation using adaptive interpolation (in which, different interpolation filter tap weights is used for different symbol position) is proposed. Each set of tap weights is updated using the normalized least mean square (NLMS) algorithm, the reference signal for which is obtained by decision feedback and reverse modulation of the received data symbol. In order to reduce the number of tap weight sets and to achieve fast convergence, the conjugate centrosymmetry property of the tap weight set is used. The average bit error rate (BER) performance in a frequency-selective Rayleigh fading channel is evaluated by computer simulation. Also evaluated is the robustness against the frequency offset between a transmitter and a receiver.

This paper presents a novel method of designing microstrip line multi-frequencies band filters by applying the SIR (stepped impedance resonators) technology. Utilizing the S-parameter and the ABCD parameters of a two-port network is for the analysis of short-circuited and open-circuited resonators with various combinations of series and shunt sequences. By controlling the impedance ratio of the resonators, both center frequencies of the two passbands then are determined. Moreover, a global synthesis approach is also discussed on miniaturization. A simplified architecture based on bent SIR offers the 50% area reduction of layout. Technology of matching circuit creates higher performance multi-band filter. We adjust impedance and electrical length of transmission line (TL) to compensate multi-band and bending for matches and highly improve the insertion and reflection loss. Simulation and measurement are performed to validate our method and are pretty matched.

Based on the periodical-loaded principle, a new wider stop-band filter is presented. The design equations are provided, the validity of which is proved by the measured results. Compared with loaded stub of length 1/4λg, the improved T-shape stub can change admittance paralleled with microstrip line and widen the band width of the band-stop filter. The size of the filter loaded by one side can be reduced by 2/3. The stop-band filter loaded by one side and two sides are simulated and realized. The filter loaded by two sides can achieve very wide stop-band. In addition, the stop-band of the new type of filter is deep and steep.

A method is proposed to compute moments of distributed coupled RLC interconnects. Both uniform line models and non-uniform line models will be developed. Considering both self inductances and mutual inductances in multi-conductors, recursive moment computations formulae of lumped coupled RLC interconnects are extended to those of distributed coupled RLC interconnects. By using the moment computation technique in conjunction with the projection-based order reduction method, the inductive crosstalk noise waveform can be accurately and efficiently estimated. Fundamental developments of the proposed approach will be described. Simulation results demonstrate the improved accuracy of the proposed method over the traditional lumped methods.

A new microstrip compatible phase shifter circuit is introduced. The phase shifter uses a strip-type electromagnetic bandgap (EBG) substrate in place of the solid metal ground plane. Such EBG substrates, when made of ferroelectric materials, can produce variable phase constants useful for phase shifter applications. Test models using two different EBG substrates with dielectric constants of 9.2 and 10.2 showed 44.5 degrees of phase difference with 1.7 dB of added insertion loss at 10 GHz from a line originally 504 degrees long.

In VDSM era, crosstalk is becoming a more and more vital factor in high performance VLSI designs, making noise mitigation in early design stages necessary. In this paper, we propose an effective algorithm optimizing crosstalk under congestion constraint in the layer assignment stage. A new model for noise severity measurement is developed where wire length is used as a scale for the noise immunity, and both capacitive and inductive coupling between sensitive nets are considered. We also take shield insertion into account for further crosstalk mitigation. Experimental results show that our approach could efficiently reduce crosstalk noise without compromising congestion compared to the algorithm proposed in [1].

A series-fed beam-scanning array employing a MUlti-Stage Configured microstrip Antenna with Tunable reactance devices (MUSCAT) is proposed. The proposed antenna significantly expands the beam scanning range and achieves high efficiency. This antenna comprises unit element groups, whose elements are placed close to each other and employ tunable reactance devices. Analyses and experiments on the unit element groups show that their multi-stage configuration extends the phase shift range and increases the radiation efficiency, e.g., a 120phase shift and the radiation efficiency of more than 50% are achieved, when three stages are employed. The radiation pattern of the fabricated MUSCAT array antenna comprising eight unit element groups is measured. A beam scanning range of 27, which is greater than twice the beam scanning range of a non-multi-stage configuration, is achieved.

An aperture-coupled patch antenna on a modified-shape groundplane is proposed in this paper. It is applicable to the H-plane array without perpendicular feed structure. Availability of the depth-area under antenna-substrate is effectively improved by using radiation from the T-shaped element, while the advantage of aperture-coupled antenna in suppressing the spurious-feed-network radiation remains effective. Basic characteristics of the antenna are investigated through the numerical examination by using FDTD-method. As a result, the increased bandwidth is also obtained, which is observed as dual-resonance characteristics due to the T-shaped element and the aperture-fed patch. A H-plane array of the proposed element incorporating a probe-fed patch antenna is also presented to show an potential as a polarization diversity antenna.

Periodically nonuniform coupled microstrip line (PNC-ML) loaded with transverse slits is characterized using the fullwave method of moments and short-open calibration technique. Guided-wave characteristics of both even- and odd-modes are thoroughly investigated in terms of two extracted per-unit-length transmission parameters, i.e., phase constants and characteristic impedances. As such, frequency-dependent coupling between the lines of the finite-extended PNCML is exposed via two dissimilar impedances. Meanwhile, two phase constants try to be equalized at a certain frequency by properly adjusting the slit depth and periodicity, aiming at realizing the transmission zero. Further, equivalent J-inverter network parameters of this finite-length PNCML are derived to reveal the relationship between the transmission zero and harmonic resonance. By allocating this zero to the frequency twice the fundamental passband, one-stage and two-stage PNCML filters are then designed, fabricated and measured to showcase the advantageous capacity of the proposed technique in harmonic suppression.

The electrostatic discharge (ESD) effect in GMR heads in the deshunting process is studied in order to prevent the damage in this process. The simulation and experiment results are investigated and compared. It is found from these results that sequences of deshunting process, currently operating, can cause the damage of GMR heads due to the ESD effect, based on the charged device model, CDM. This also shows that the voltage across GMR head, as the tweezers is used, can be raised up to 3.7 V which is about harmful to damage the head. Examples of damage heads confirmed by the SEM are also shown.

A topological book embedding of a graph is an embedding in a book that carries the vertices in the spine of the book and the edges in the pages; edges are allowed to cross the spine. Enomoto showed that for any graph G having n vertices, there exists a three-page book embedding of G in which each edge crosses the spine log n times. This paper generalizes the result and shows that for any graph G having n vertices, there exists a d + 1-page book embedding of G in which each edge crosses the spine logd n times.