In all-optical switches using the cascade of second harmonic generation and difference frequency mixing in periodically poled lithium niobate (PPLN) waveguide devices, walk-off between the fundamental and second harmonic pulses causes crosstalk between neighboring symbols, and limits the switching performance. In this paper, we numerically study retiming characteristics of all-optical switches that employ the PPLN waveguide devices with consideration for the effects of the crosstalk and for the input timing of the data and clock pulses. We find that the time offset between the data and clock pulses can control the timing jitter of the switched output; an appropriate offset can reduce the jitter while improving the switching efficiency.

New target specific absorption rate (SAR) values, calculated using a proposed reference dipole antenna and the reference flat phantom, are presented for an SAR validation test at 150MHz. The reference flat phantom recommended by the International Electrotechnical Commission (IEC) standard for 150MHz requires a significant amount of liquid owing to its large size. We conduct a numerical analysis in order to reduce the size of the flat phantom. The optimum size of the flat phantom is 780 (L1) × 540 (W) × 200 (H)mm3, which is approximately a 64% reduction in volume compared to the reference flat phantom. The length of the reference dipole antenna required for the optimized flat phantom (extrapolated from the reference values at 300MHz) becomes 760mm. The calculated and measured return losses (S11) of the antenna at 150MHz are 24.1dB and 22dB, respectively. The calculated and measured results for the return loss of the dipole antenna agree well and satisfy the IEC standard (> 20dB). The target SAR values derived from the numerical analysis are 1.08W/kg for 1g of tissue and 0.77W/kg for 10g of tissue for an SAR validation test at 150MHz.

An imbalance difference model has been developed to estimate the common-mode radiated emission of a PCB with an attached cable. This model, however, requires significant computation time for full-wave simulation, especially if the attached cable is long, even with a powerful computer configuration. To solve this problem, a method that approximates the imbalance difference model as an equivalent asymmetrical dipole antenna is proposed in this paper. The common-mode radiated emission can be predicted using a line integration of the common-mode current distribution which is directly estimated by the asymmetrical antenna model. Unlike existing methods, the proposed method avoids the circuit construction normally used to measure the common-mode current, and is still able to accurately predict the maximum common-mode radiation. The effectiveness of the proposed method is verified by comparing the predicted results with the 3D full-wave simulation and the measured data gathered in an anechoic chamber.

We propose that the current distribution along a dipole can be divided into a component proportional to the port current, a component proportional to the port voltage, and an antisymmetrical component. In this paper, we perform numerical computations to verify that the component proportional to the port voltage always lags the port voltage by 90°, and the ratio of its amplitude to that of the port voltage is not significantly affected by the arrangement of other dipoles located nearby or by circuits connected to the ports of the dipoles if the dipoles have lengths not exceeding one wavelength.

The fast multipole method (FMM) for N-body simulations is attracting much attention since it requires minimal communication between computing nodes. We implemented hardware pipelines specialized for the FMM on an FPGA device, the GRAPE-9. An N-body simulation with 1.6×107 particles ran 16 times faster than that on a CPU. Moreover the particle-to-particle stage of the FMM on the GRAPE-9 executed 2.5 times faster than on a GPU in a limited case.

Two types of 3D folded dipole antenna with feed line (FDAFL) were reported for a small terminal, which covered WiMAX 2.5/3.5GHz bands and WLAN 2.4GHz band. In this study, folded monopole antenna (FMA) is proposed as a variant of FDAFL. We show the broadband characteristics of FMA and determine the most suitable configuration of FMA array for realizing MIMO system. Also, a multiband variant is created by introducing a parasitic element to FMA. The result is a multiband FMA array with parasitic elements operating at 5GHz band of WiMAX and WLAN as well as WiMAX 2.5/3.5GHz bands and WLAN 2.4GHz band with total antenna efficiency of between 70% to 96% and the envelope correlation coefficient of less than 0.02. Finally, a prototype antenna is implemented, and we confirm the validity of the simulation by comparison to measured results.

This paper proposes a new small multiband printed antenna for wireless telecommunications modules that can realize Machine-to-Machine applications. We reconfigure our previous antenna to cover the 700MHz, 800MHz, and 900MHz bands, and add two new elements (second strips) to cover the 2GHz band. The new antenna achieves operation in quad-bands: 700MHz, 800MHz, 900MHz, and 2GHz. Frequency characteristics are analyzed using electromagnetic-simulation software based on the method of moments, and the validity of the numerical results is shown based on measured Voltage Standing Wave Ratio (VSWR) characteristics and the radiation patterns of a prototype antenna. The proposed antenna is compact with a VSWR bandwidth (≤2) of 27.5% in bands including 700MHz, 800MHz, and 900MHz, and a VSWR bandwidth (≤2) of 10.6% in the band including 2GHz. We clarify that the operating mechanism in the 2GHz band is equivalent to that of a one wavelength folded offset fed dipole antenna comprising a monopole element and second strips, and that the operating frequency in the 2GHz band can be determined by the path length from the tip of the monopole element to the tip of the second strip via a feeding point.

This paper presents an approximated virtual source imaging system based on crosstalk cancellation with a pair of closely spaced loudspeakers. Utilizing the frequency-dependent relative importance of sound localization cues, the proposed system provides separate approximations for the low- and high-frequency bands. Experimental results show that the system provides good approximations within ±55° in the stereo dipole setup with natural sound quality.

To implement a wideband bandpass filter with improved skirt-selectivity and out-band characteristics, a new parallel-coupled three-line unit with two short-circuited stubs symmetrically-loaded at the center line is proposed. Unlike most traditional ones, the passband of the proposed parallel-coupled three-line structure is based on the cross-coupling between non-adjacent lines rather than the direct-coupling between adjacent ones, whereas a pair of attenuation poles is found in the stopbands. After revealing its work mechanism, an efficient filter-design-scheme is correspondingly proposed for the presented structure. Firstly, based on a chebyshev-filter synthesis theory, a wideband passband filter consisting of a parallel-coupled two-line and two short-circuited stubs loaded at the input- and output- ports is designed. Furthermore, by putting a properly-designed 3/4-wavelength stepped-impedance resonator (SIR) in between the parallel-coupled two lines, two attenuation poles are then realized at the frequencies very close to the cutoff ones. Accordingly, the roll-off characteristics of the filter are significantly-improved to greater than 100,dB/GHz. Furthermore, two-section open-ended stubs are used to replace the short-circuited ones to realize a pair of extra attenuation poles in stopbands. To validate the proposed techniques, a wideband filter with a bandwidth of 3--5,GHz (Fractional bandwidth (FBW) $= (5,GHz-3,GHz)/4,GHz =50%)$ was designed, simulated, fabricated and measured. The measured responses of the filter agree well with the simulation and theoretical ones, which validates the effectiveness of the newly-proposed three-line unit and the corresponding design scheme.

This paper presents a new technique to enhance the bandwidth of a printed dipole antenna for ultra-wideband applications. The basic idea is to exploit mutual coupling between the feeding line, which is designed closed and paralleled to dipole arms, the dipole arms and other elements of the antenna. Dipole arms, feeding lines as well as other parts are investigated in order to expand antenna bandwidth while still retaining antenna compactness. Based on the proposed technique, we develop two sample printed dipole antennas for advanced wireless communications. One is an ultra-wideband antenna which is suitable for multi-band-mode ultra-wideband applications or being a sensing antenna in cognitive radio. The other is a reconfigurable antenna which would be applicable for wideband cognitive radios. Antenna characteristics such as radiation patterns, current distributions, and gains at different frequencies are also investigated for both sample antennas.

Folded dipole antenna with feed line (FDAFL) whose relative bandwidth is 65% (VSWR≤3) has been reported as a wideband planar antenna for a small terminal. However, this antenna is constructed outside of the ground plane (50×80mm2) by 12mm. In this study, we analyze the antenna configurations of FDAFL in 3D so that the antenna does not protrude from the ground plane as much as possible. Two different 3D antenna models derived from FDAFL are investigated. The first model is folded over the ground plane, and the second one is folded outside of the ground plane. The relative bandwidth, the VSWR characteristics and radiation patterns are studied. As a result, it is confirmed that antenna prominence could be reduced and broadband characteristics over 74% and 83% are obtained by the 3D models, respectively, which are wider than the bandwidth of conventional 2D model. Thus, FDAFL could be used in both 2D and 3D for a small terminal.

The simple repetitive control system proposed by Yamada et al. is a type of servomechanism for periodic reference inputs. This system follows a periodic reference input with a small steady-state error, even if there is periodic disturbance or uncertainty in the plant. In addition, simple repetitive control systems ensure that transfer functions from the periodic reference input to the output and from the disturbance to the output have finite numbers of poles. Yamada et al. clarified the parameterization of all stabilizing simple repetitive controllers. Recently, Yamada et al. proposed the parameterization of all stabilizing two-degrees-of-freedom (TDOF) simple repetitive controllers that can specify the input-output characteristic and the disturbance attenuation characteristic separately. However, when using the method of Yamada et al., it is complex to specify the low-pass filter in the internal model for the periodic reference input that specifies the frequency characteristics. This paper extends the results of Yamada et al. and proposes the parameterization of all stabilizing TDOF simple repetitive controllers with specified frequency characteristics in which the low-pass filter can be specified beforehand.

This paper clarifies the effects of metal wires placed around a Multiple-Input-Multiple-Output (MIMO) array with the goal of improving the channel capacity in near-field MIMO systems. Tests are performed on dual-dipole arrays with metal wires placed parallel to the dipoles. If the antenna elements have an appropriate half-power beamwidth (HPBW), there is a clear improvement in the channel capacity of the dual-dipole array. The metal wires are used to increase the multipath richness and the locations of the wires significantly impact the channel capacity. A significant increase in the channel capacity is observed even if only one metal wire is placed in the proper location. We verified the generality of applying a metal wire to improve the channel capacity and that the improvement in the channel capacity is approximately proportional to the number of metal wires.

The problem of a finite monopole antenna driven by a coaxial cable is revisited. On the basis of a variable bound approach, the radiated field around a monopole antenna can be represented in terms of the discrete modal summation. This theoretical model allows us to avoid the difficulties experienced when dealing with integral equations having different wavenumber spectra and ensures a solution in a convergent series form so that it is numerically efficient. The behaviors of the input admittance and the current distribution to characterize the monopole antenna are shown for different coaxial-antenna geometries and also compared with other existing results.

After brief introduction of our new microscope unit with an immersion objective and ionic liquid used as a refractive index matching medium, in this paper, we describe the studies on dipole orientation imaging of single molecules under high vacuum conditions as one of the important applications of our microscope.

Current distributions induced on a circular disk of conductor are analyzed rigorously for an electric dipole incidence, when the source dipole is polarized parallel to the disk and located at an arbitrary position, and they are evaluated numerically. As the height of the dipole increases, the current distribution of the dipole approaches that of the plane wave incidence. Using a multiple precision arithmetic, numerical data for the current distribution are obtained for larger radii of a disk than the former approach.

In this letter, a novel ultra-wideband circular quasi-fractal monopole antenna with a six-petaled lotus pattern is presented. The CPW-fed technique and quasi-fractal concept are used to achieve ultra-wideband characteristics. The size of the proposed antenna is 4250 mm2 with a lotus diameter of 19.8 mm. The proposed antenna exhibits ultra-wideband characteristics from 2.65 to 12.72 GHz, which corresponds to a fractional bandwidth of 131%. The measured radiation pattern of the proposed antenna is nearly omnidirectional.

A folded monopole antenna fed by a CPW-to-trident transition feeder for compact wireless USB dongle devices is proposed. The antenna's dimensions are 1644.83.5 mm3, so it is suitable for low-profile wireless USB dongles. The proposed, compact monopole antenna resonates from 2.28 GHz to 10.8 GHz; hence, it can cover all wireless bands including WiBro (2.3–2.4 GHz), Bluetooth (2.4–2.484 GHz), WiMAX (2.5–2.7 GHz and 3.4–3.6 GHz), satellite DMB (2.605–2.655 GHz), 802.11b/g/a WLAN (2.4–2.485 GHz and 5.15–5.825 GHz), and UWB (3.1–10.6 GHz). A fabricated antenna is tested on a laptop to investigate the effects of the keypad and LCD screen on the resonant frequency and radiation pattern. The measured average gain of the fabricated antenna ranges from -2.76 dBi to 0.72 dBi.

The Direct Sampling Mixer (DSM) with a complex coefficient transfer function is demonstrated. The operation theory and the detail design methodology are discussed for the high order complex DSM, which can achieve large image rejection ratio by introducing the attenuation pole at the image frequency band. The proposed architecture was fabricated in a 65 nm CMOS process. The measured results agree well with the theoretical calculation, which proves the validity of the proposed architecture and the design methodology. By using the proposed design method, it will be possible for circuit designers to design the DSM with large image rejection ratio without repeated lengthy simulations.

This paper presents a new common-mode stabilization method for a CMOS differential cascode Class-E power amplifier with LC-tank based driver stage. The stabilization method is based on the identification of the poles and zeros of the closed-loop transfer function at a critical node. By adding a series resistor at the common-gate node of the cascode transistor, the right-half-plane poles are moved to the left half plane, improving the common-mode stability. The simulation results show that the new method is an effective way to stabilize the PA.