In Chirp-Pulse Microwave Computed Tomography (CP-MCT) the images are affected by the blur which is inherent to the measurement principle and is described by a space-variant Point Spread Function (PSF). In this paper we investigate the PSF of CP-MCT including the space dependence both experimentally and computationally. The experimental evaluation is performed by measuring the projections of a target consisting of a thin low-loss dielectric rod surrounded by a saline solution and placed at various positions in the measuring region. On the other hand, the theoretical evaluation is obtained by computing the projections of the same target via a numerical solution of Maxwell's equations. Since CP-MCT uses a chirp signal, the numerical evaluation is carried out by the use of a FD-TD method. The projections of the rod could be obtained by computing the field during the sweep time of the chirp signal for each position of the receiving antenna. Since this procedure is extremely time consuming, we compute the impulse response function of the system by exciting the transmitting antenna with a wide-band Gaussian pulse. Then the signal transmitted in CP-MCT is obtained by computing the convolution product in time domain of the input chirp pulse with the impulse response function of the system. We find a good agreement between measured and computed PSF. The rationality of the computed PSF is verified by three distinct ways and the usefulness of this function is shown by a remarkable effect in the restoration of CP-MCT images. Knowledge on the space-variant PSF will be utilized for more accurate image deblurring in CP-MCT.

A highly sensitive optical sampling system has been produced by using sum-frequency generation in a periodically poled lithium niobate crystal. When the relations between crystal length and wavelength bandwidth and SFG conversion efficiency were investigated theoretically and experimentally, a system with a 1.4-mm-long periodically poled lithium niobate crystal was found to have a 22.5-nm wavelength bandwidth and a SFG conversion efficiency ten times that of a similar system with a 3-mm-long KTP crystal. The SNR of the system with the 1.4-mm-long PPLN crystal was about 7 dB higher than that of the system with a 3-mm-long KTP crystal, and a temporal resolution better than 1 ps was obtained by using compressed optical sampling pulses. The eye diagram of a 10-Gbit/s RZ optical signal with a 1-mW peak power could be observed, and the eye diagram of a 160-Gbit/s RZ optical signal could be observed clearly.

Two planar asymmetric coupled waveguides were fabricated by using different materials (InGaAsP and TiO2/Si) and tested as dispersion compensators (or pulse compressors). Compression of a more-than-10-ps chirped pulse is experimentally demonstrated by using an InGaAsP planar asymmetric coupled waveguide whose group velocity dispersion (GVD) is enhanced by structural optimization and is spectrally tuned to an input pulse as precisely as possible. A large polarization dependence of the pulse compression was also observed and indicates that the observed pulse compression results from dispersion compensation due to the GVD associated with supermodes. A new planar, asymmetric coupled waveguide with a large difference in refractive indices of the two waveguides was fabricated by using a combination of dielectric (TiO2) and semiconductor (Si) materials in order to obtain better GVD characteristics than semiconductor (for example, InGaAsP) asymmetric coupled waveguides. A preliminary experiment on pulse compression using the TiO2/Si planar asymmetric coupled waveguide was conducted. A 2.8-ps blue chirped pulse was compressed down to about 1 ps by a 1-mm-long waveguide (compression ratio: 0.375, which is better than those of the previous InGaAsP planar asymmetric coupled waveguides). This compression ratio agrees well with a theoretical result obtained by a numerical model based on a supermode's GVD.

Recent activities on ultrafast photonic device technology development in the Femtosecond Technology Project sponsored by NEDO are introduced. Topics include management and control of the higher order dispersions of optical fibers, ultrafast mode-locked semiconductor laser, symmetric Mach-Zehnder type all-optical switch, ultrafast serial-to-parallel signal converter and sub-picosecond wavelength switch. Challenges towards novel ultrafast switching material systems are also described.

The concept of stochastic association has originally been proposed in relation to single-electron devices having stochastic behavior due to quantum effects. Stochastic association is one of the promising concepts for future VLSI systems that exceed the conventional digital systems based on deterministic operation. This paper proposes a CMOS stochastic associative processor using PWM (pulse-width modulation) chaotic signals. The processor stochastically extracts one of the stored binary patterns depending on the order of similarity to the input. We confirms stochastic associative processing operation by experiments for digit pattern association using the CMOS test chip.

A new ramped-square sustain waveform is proposed to improve both the luminance and the luminous efficiency of an alternate current plasma display panel (ac PDP). The luminous characteristics such as the luminance and luminous efficiency have been measured with a square-voltage and a ramp-voltage (or voltage slope) of the proposed sustain pulse. With an increase in the square-voltage of a ramped-square sustain waveform, the luminance increases but the luminous efficiency decreases. On the other hand, with an increase in the ramp-voltage of a ramped-square sustain waveform, both the luminance and the luminous efficiency increase. When compared with the conventional square sustain waveform, an improved luminance of 22% and luminous efficiency of 36% are simultaneously obtained based on the proper adjustment of the square-voltage and ramp-voltage of the ramped-square sustain waveform in a 4-inch ac PDP test panel at a frequency of 62 kHz.

A priming effect is studied for a three-electrode, surface-discharge AC-PDP, which has stripe barrier ribs of 0.22 mm pitch. It was found that by keeping the interval between the reset and address pulses within 24 µs, the data pulse voltage can be reduced while the data pulse width can be narrowed due to the priming effect. By adopting the primed addressing technique to the PDP, the data pulse voltage was reduced to 20 V when the data and scan pulse widths were 1 µs. Alternatively, the data pulse width could be narrowed to 0.33 µs when the data pulse voltage was 56 V. 69% of the TV field time could be assigned for the display periods with 12 sub-fields, assuring high luminance display.

We present a novel kind of integrate-and-fire circuit (IFC) with two periodic inputs: a pulse-train stimulation input and a base input. We clarify that the system state is quantized by the pulse-train stimulation input. Then the system dynamics is described by a return map with quantized state (Qmap). By changing the shape of the base input, various Qmaps can be obtained. The Qmap exhibits co-existence state of various super-stable periodic orbits, and the IFC outputs one of corresponding super-stable periodic pulse-trains depending on the initial state. For a typical case, we clarify the number of co-existing periodic pulse-trains theoretically for the stimulation frequencies. Constructing a simple test circuit, typical phenomena can be verified in the laboratory.

This document analyzes the characteristics of Waiting Time Jitter (WTJ) generated in High-bit-rate Digital Subscriber Lines (HDSL) systems transmitting non-uniform frames. It also derives the Fourier transform of the above WTJ.

Two isolated pulse models, the Lorentzian-like and the Mixture model, were used to investigate the effect of GMR heads-media with different geometric and magnetic parameters on the readback pulse shape. The matching of these two models with an actual pulse was compared in detail. The dependence of the readback pulse shape of GMR head on the head-media parameters and non-linear distortions was discussed in this paper. When applying these models to evaluate the performance of a recording system, it is necessary to take into account of the difference between the linear superposition of the isolated pulse and the actual readback data pattern. It was suggested to linearize the captured isolated pulse in order to use the model correctly as a useful tool for evaluating the system performance.

The ultrasonic wave is widely used for acquiring perceptual information necessary for indoor/outdoor navigation of mobile robots, where the system is implemented as a sound navigation and ranging system (sonar). A robot equipped with multiple ultrasonic sonars is likely to exhibit undesirable operation due to erroneous measurements resulting from cross-talk among the sonars. Each sonar transmits and receives a pulse-modulated ultrasonic wave for measuring the range and identifying its own signal. We propose a technique for generating pulse patterns for multiple concurrently operated ultrasonic sonars. The approach considers pulse-pattern generation as a combinatorial optimization problem which can be solved by a genetic algorithm (GA). The aim is to acquire a pulse pattern satisfying certain conditions in order to avoid cross-talk or keep the probability of erroneous measurement caused by cross-talk low. We provide a method of genotype coding for the generation of the pulse pattern. Furthermore, in order to avoid a futile search encountered when the conventional technique is used, we propose an improved genotype coding technique that yields considerably different results from those of the conventional technique.

In this paper, we compare the major issues associated with TDMA and S-CDMA (Synchronous-Code Division Multiple Access), which is considered as a new cable modem standard technology for upstream channel. We mainly deal with the following 3 topics: MAC protocol, modem structure and BER (Bit Error Rate) performance comparison between TDMA and S-CDMA. Especially, we derive BER of TDMA and S-CDMA schemes in the ε-mixture impulse noise model which appropriately reflects impulse noise characteristics of the upstream channel by using various parameters.

This paper studies an integrate-and-fire circuit with a periodic input. It has two states and has rich dynamics: as a DC input varies, it can exhibit period doubling bifurcation to chaos; as a periodic input is applied, the periodic or chaotic phenomenon (for a DC input) is changed into interesting synchronous or asynchronous phenomenon. Using a mapping procedure, we can elucidate parameter subspace in which the synchronous phenomena occur. Using a test circuit, typical phenomena can be verified in the laboratory.

This paper describes a simple polarization-independent wavelength conversion method using degenerated four-wave mixing (FWM) in single-mode fibers pumped with cross-polarized high frequency, saw-tooth pulses from a single pump source. Successful polarization-independent wavelength conversion is experimentally confirmed with less than 12% and 5.6% variation using a gain-switched LD pumping and a mode-locked fiber laser pumping, respectively. We clarify that the interference effect between two orthogonal pump pulses must be taken into account to achieve a good polarization-insensitive operation, since even the small pulse edges bring about the large polarization fluctuations when they are interfered. Furthermore, it is reveal that the shorter pump pulse broadens its own spectrum due to the self-phase modulation in fibers, resulting in poor FWM efficiency. Finally, possibility of high-speed operation is discussed taking into account the pump pulse conditions.

This paper describes a simple polarization-independent wavelength conversion method using degenerated four-wave mixing (FWM) in single-mode fibers pumped with cross-polarized high frequency, saw-tooth pulses from a single pump source. Successful polarization-independent wavelength conversion is experimentally confirmed with less than 12% and 5.6% variation using a gain-switched LD pumping and a mode-locked fiber laser pumping, respectively. We clarify that the interference effect between two orthogonal pump pulses must be taken into account to achieve a good polarization-insensitive operation, since even the small pulse edges bring about the large polarization fluctuations when they are interfered. Furthermore, it is reveal that the shorter pump pulse broadens its own spectrum due to the self-phase modulation in fibers, resulting in poor FWM efficiency. Finally, possibility of high-speed operation is discussed taking into account the pump pulse conditions.

An improved pulse shaper is proposed which is able to control both the spatial and temporal profile of femtosecond light pulses. Our pulse shaper exploits the spatio-temporal coupling effect seen in pulse shapers. Its properties are numerically analyzed by application of the Wigner distribution function. We confirm that the spatio-temporal output pulse track dictates the differentiation of the phase mask; that the degree of spatio-temporal coupling is determined by the focal length ratio of the lenses in the pulse shaper; and that space to spatial-frequency chirp results from misalignment of lenses.

A merged analog-digital circuit architecture is proposed for implementing intelligence in SoC systems. Pulse modulation signals are introduced for time-domain massively parallel analog signal processing, and also for interfacing analog and digital worlds naturally within the SoC VLSI chip. Principles and applications of pulse-domain linear arithmetic processing are explored, and the results are expanded to the nonlinear signal processing, including an arbitrary chaos generation and continuous-time dynamical systems with nonlinear oscillation. Silicon implementations of the circuits employing the proposed architecture are fully described.

This paper presents the design and simulation of a power efficient 1:4 interpolation FIR filter with partitioned look Up Table (LUT) structure. Using the symmetry of the filter coefficients and the contents of the LUT, the area of the proposed filter is minimized. The two filters share the partitioned LUT and activate the LUT selectively to realize the low power operation. Experimental results suggest that the proposed filter reduces the power consumption by 25% and simultaneously reduces the gate area by 7% compared to the previously proposed single-architecture dual-channel filter.

The alignment of a nematic liquid crystal (LC) parallel to the polarization direction of the laser could be induced by three types of polyimide (PI) films, a PI based on aromatic dianhydride and two PIs on alicyclic dianhydride, exposed to polarized pulsed laser at 266 nm at high fluence in air. The UV-visible absorption spectra of the PI films showed that a remarkable chemical change occurred after exposure at the high fluence in air. In contrast, in argon atmosphere the PI based on aromatic dianhydride was radiation-resistant and the exposed PI film could induce alignment of the LC molecules parallel to laser polarization. We estimate that the mechanism of the parallel alignment observed in argon is not the photodegradation but the orientation of the PI molecules.

The use of a chirp signal is one of the methods to expand the detection range in subsurface radar. However, the presence of time-sidelobes after a conventional pulse-compression makes the detection range degraded because weak signals from underground objects are covered with a large time-sidelobe due to a ground surface reflection. In this paper, we propose a new pulse compression subsurface radar using a short chirp signal in which the echoes from the ground surface and the object are not overlapped. We show that the short chirp signal can improve the detection ability compared with a conventional chirp signal and examine the influence that the decreases of the signal duration and the compression ratio exert on the detection range. By the new pulse compression subsurface radar, the steel pipes buried down to 5 m in depth can be detected.