One of the most basic characteristics of the image is accompanied by its blur. It was 1962 that I had discovered for the first time in the world that the blur was a Gaussian type. In this paper the outline is described about historical details concerning this circumstances.

A novel optical modulation scheme is proposed for synthesizing a pair of dual-mode optical BPSK signals with an orthogonal phase relationship via a LiNbO3 Mach-Zehnder modulator (MZM) with dual RF signal inputs and a carrier suppression feature, which enables the generation of a crosstalk-free QPSK signal at the photodetection stage. With this method, one can compensate the drawback, that is bandwidth broadening, in our previously proposed method where a dual-mode optical QPSK signal is generated on the basis of narrow-angle modulated QPSK signal injection into a double-sideband suppressed carrier MZM device. We have carried out experiments for 60 GHz performance demonstration of this QPSK signal generation mechanism, and the results indicate the effectiveness of the present scheme.

A frequency-tuning method in the microwave region, which maintains a high unloaded Q-factor, was demonstrated using a double-sapphire-loaded cavity which operates on the Whispering Gallery mode, WGH9,1,0. Two adjacent nominally identical sapphire cylinders were positioned in a copper cavity and tuned by changing their relative coupling. A frequency tuning range of 85 MHz and a maximum unloaded Q-factor of 1.3 105 was experimentally measured at room temperature. This is only 13% less than the single resonator Q-factor, which is a small compromise to pay for the increased tuning capacity.

A decentralized estimation system usually contains a number of remotely located local sensors that can pre-process observed signal and convey the processed data to a fusion center that makes a final estimation. The local sensors are linked to the data fusion center by transmission channels. When the observation (or estimate of parameter) is quantized at the peripheral sensors and an assumption of conditionally independent sensor data is made, due to potential communication constraints on the channels, the problem of quantization design and bandwidth allocation among the channels linking local sensors to the fusion center is studied in this letter.

A new CMOS 1/x circuit is presented in this letter. The output amplitude of the proposed circuit can be adjusted by a bias current. The proposed circuit can be used to realize a current-to-voltage converter and a current-mode divider. The proposed circuits have been fabricated in a 0.5 µm CMOS process. Experimental results show that under the linear error less than 1%, the input range of the proposed 1/x circuit can be up to 1.5 V for the supply voltages of 1.5 V and the power dissipation is 0.24 mW. The experimental results are given to demonstrate the proposed circuits.

Binary and ternary 5-bit programmable dispersion matrix, based on fiber Bragg reflectors, is built to control a two-channel receive/transmit beamformer at 1550 nm. RF phase measurements for the 32/31 delay configurations are presented. The programmable dispersion matrix is fully demonstrated and characterized for RF signals from 0.2 to 1 GHz.

A mobile station (MS) positioning method using signal strength is an algorithm to estimate the geographical position of a target MS based on measured strength of signals transmitted to/from the MS from/to multiple base stations (BSs) at known geographical positions. This paper proposes a novel MS positioning method using signal strength in cellular systems. The primary sources of position location error for positioning methods using signal strength are multipath fading and shadowing. Although signal strength averaging can help to reduce the effect of multipath fading, the effect of shadowing still remains. In order to eliminate the error caused by shadowing, the proposed method applies a statistical approach and a minimum mean squared error (MMSE) criterion to determine a position estimate. The performance of the proposed method is compared to that of a maximum likelihood (ML) positioning method and a cell-site positioning method. The performance is obtained by computer simulations and field experiments. A computer simulation result shows that the proposed method can determine position estimates in higher probability than the ML method. Also, it is shown that the proposed method provides higher accuracy than the ML method and the cell-site method.

This paper focuses on a global ultrasonic system for self-localization of a mobile robot. The global ultrasonic system consists of some ultrasonic generators fixed at some arbitrary position in the global coordinates and two receivers in the moving coordinates of the mobile robot. This system is used to obtain the state vector of the mobile robot in the global coordinates from the distance measurement between the ultrasonic generator and the receiver. In order to avoid the cross-talk and to synchronize the ultrasonic sensors, the sequential cuing technique using small-sized radio frequency module is adopted. An extended Kalman filter algorithm is used to process the noisy ultrasonic signal and to estimate the state vector. Computer simulations and experiments are conducted to verify the effectiveness of the proposed global ultrasonic system.

In the paper, we propose a new method for chromatic dispersion measurement of WDM components in both transmission and reflection, employing photonic microwave technology. The dispersion can be determined by measuring the frequency spectrum range change of the microwave notch filter. The method features the advantages of low-cost and simplicity. Experimental results demonstrate that our setup is capable of measuring relative group delay with better than 1 ps time resolution and the measurement results show a good agreement with that measured by the conventional phase-shift technique.

In our previous research, we proposed a nonlinear digital filter to Estimate the Smoothed and Differential values of the sensor inputs by using Sliding mode system (ESDS). This estimator is able to eliminate impulsive noise efficiently from time series data. We applied this filter to processing outputs of robot sensors, and it became possible to perform robust environment recognition. ESDS is designed using a theory of variable structure system (VSS) with sliding mode. In short, ESDS is a nonlinear filter. Therefore, it is very difficult to clarify the behavior of the system analytically. Consequentially, we deal with the step function with impulsive noise as an example, and we attempt to eliminate this impulsive noise by keeping the sudden shift of signals. In this case, there is a trade-off between the noise elimination ability and the tracking performance for an input signal. Although ESDS is a nonlinear filter, it has the same trade-off as linear filters such as a low-pass filter. In order to satisfy these two conditions simultaneously, we use two filters whose parameters are independent of each other. Furthermore, in order to repress the adverse affect of impulsive noise in the steady-state, we introduced the boundary layer. Generally, a boundary layer is used so as to inhibit the harmful effect of chattering. Chattering is caused in the sliding mode system when the state of the system vibrates on the switching line of a sliding mode system. By introducing the boundary layer to ESDS, we can repress the adverse effect of impulsive noise in the steady-state. According to these considerations, we clarify the relationship between these characteristics of ESDS and the arbitrary parameters.

In this paper, we propose a simple method to find the optimal rational function, with a fixed denominator, which minimizes an integral of polynomially weighted squared error to given analytic function. Firstly, we present a generalization of the Walsh's theorem. By using the knowledge on the zeros of the fixed denominator, this theorem characterizes the optimal rational function with a system of linear equations on the coefficients of its numerator polynomial. Moreover when the analytic function is specially given as a polynomial, we show that the optimal numerator can be derived without using any numerical integration or any root finding technique. Numerical examples demonstrate the practical applicability of the proposed method.

We investigate the capacity limitations of a WDM ring fiber-radio backbone incorporating wavelength interleaving where each base station drives a sectorized antenna interface. We also investigate the issues related to the merging of such networks with standard WDM infrastructures. The investigations show that re-allocating the interleaved WDM channels to fit within a 100 GHz block enables the millimeter-wave (mm-wave) fiber-radio system with sectorized antenna interfaces to integrate easily with WDM systems. The performance of a variety of channel allocations for the merged fiber-radio network is examined and simulation studies of the transmission of multiple channels are carried out. The overall network capacity of the merged mm-wave fiber-radio network is improved with the proposed channel allocation schemes.

In this paper, an optical signal processing beam forming network (BFN) for two-dimensional (2-D) beam steering is proposed and experimentally demonstrated. Two lightwaves, called the signal and reference, are both Fourier transformed, combined, and then down-converted into RF signals using an optical heterodyne technique. A simple combination of orthogonal one-dimensional position scannings of the signal and reference lightwaves generates RF signals with phase distributions for 2-D beam steering. The system operation and optical losses are theoretically analyzed. Using graded index fiber (GIF) lensed single mode fibers (SMFs), total optical loss of the sampling fiber array is evaluated to be 4.5 dB from the fiber to fiber loss measurements. Using an experimental optical signal processing BFN at 25 GHz, 2-D beam steering is demonstrated at 0, 10, 20, and 30through the measured amplitudes and phases of RF signals for 16 position sets of the signal and reference fibers. The proposed method has the potential to provide ultra-fast beam scanning by utilizing optical switching technologies.

Many fuzzy traffic controllers adjust the extension time of the green phase with the fuzzy input variables, arrival and queue. However, in our experiments, we found that the two input variables are not sufficient for an intersection where traffic flow rates change and thus, in this paper, traffic volume is used as an additional variable. Traffic volume is defined as the number of vehicles entering an intersection every second. In designing a fuzzy traffic controller, an ad-hoc approach is usually used to find membership functions and fuzzy control rules showing good performance. That is, initial ones are generated by human operators and modified many times based on the results of simulation. To partially overcome the limitations of the ad-hoc approach, we use genetic algorithms to automatically determine the membership functions for terms of each fuzzy variable when fuzzy control rules are given by hand. The experimental results indicate that a fuzzy logic controller with volume variable outperforms conventional ones with no volume variable in terms of the average delay and the average velocity. Also, the controller shows better performance when membership functions generated by a genetic algorithms instead of ones generated by hand are used.

In this paper, a novel flexible photonic microwave filter architecture based on the use of laser arrays and the periodicity of N N arrayed waveguide gratings (AWG) optical response is proposed. Independent filter response coarse and fine tuning as well as reshaping of each transversal filter response have been experimentally demonstrated showing an excellent agreement with theory.

In this paper, we propose a new configuration to implement transversal filters with negligible temperature sensitivity and low cost. These microwave filters are based on uniform fibre Bragg gratings as slicing elements of a broadband optical source. By using a tapered fibre Bragg grating as a delay line, we show that the temperature effects are the same over each component of the RF-filter. Therefore, it is possible a total cancellation of the thermal effects. The performance of these filters is compared to previous techniques, such as a laser array approach.

We investigated a tunable delay-line using an optical single-sideband modulator and an optical fiber loop. The single-sideband modulator consists of four optical modulators and an RF electric signal source. The fiber loop has a fiber Bragg grating and a couple of optical circulators. The number of times light circulates in the loop depends on the frequency of the rf-signal fed to the modulators. By using numerical simulations, we discussed the deformation of the waveform in the delay-line due to the fiber Bragg gratings, the modulators and the optical amplifiers put in the loop.

We report on several photoconductive (PC) geometries for the generation of both guided-wave and free-space terahertz (THz) waveforms. It is found that guided-wave THz electrical waveforms can be produced through both PC self-switching and frozen wave generation--eliminating the need for an ultrashort carrier lifetime in the semiconductor substrate. The concept of PC switching is also applied to the generation of free-space THz waveforms, and various ZnSe detectors are investigated as potential electro-optic THz sensors.

The system uses spectral shaping of a supercontinuum source followed by wavelength-to-time mapping to generate ultra wideband RF waveforms with arbitrary modulation. It employs an adaptive computer control to mitigate the non-ideal features inherent in the optical source and in the spectrum modulation process. As proof of concept, ultra-wideband frequency hopped CDMA waveforms are demonstrated.

The emerging multimedia applications for future mobile communication systems typically require highly diversified Quality of Service (QoS). However, due to the time and location dependent fluctuating nature of radio resources in the radio link, it is very difficult to maintain a constant level of QoS with the current end-to-end QoS control only. Therefore, wireless-aware QoS is the key issue for achieving better end-end QoS. In this paper, a new wireless QoS scheme for a joint CDMA/NC-PRMA cellular system are proposed considering QoS prioritization mechanism, users' diversified requirements and the harmonization with IP-QoS. Two wireless QoS-aware resource allocation algorithms are proposed to support QoS prioritization while achieving high radio resource utilization. By introducing a set of new QoS resource request parameters (minimum, average and maximum requirements), the algorithms can assign radio resource in a more flexible way than the conventional fixed resource allocation. Computer simulations indicate that the proposed QoS algorithms exhibit superior performance with respect to packet dropping probability for realtime application users, and improve transmission rate for non-realtime application users, which evince the effectiveness of the proposed wireless QoS algorithms.