To perform a high-speed measurement of a two-dimensional electric-field distribution, we developed an electric-field scanning system using a large-aperture electro-optic crystal and a laser-beam scanner. In the system, a two-dimensional electric-field image projected onto the crystal is read off using beam scanning through an electro-optic effect. With the imaging system, only 20 to 40 seconds are needed to obtain both millimeter-wave amplitude and phase images of a 20 30 mm area with a pixel spacing of 0.5 mm. We measured radiation patterns of a 10-GHz dipole antenna and compared them with simulation results to investigate a disturbance of the patterns inside the crystal. Profiles of a 120-GHz millimeter-wave beam were also measured to determine the effects of a dielectric lens used to focus the beam. Furthermore, we applied the system to imaging several objects with 180-GHz millimeter waves and experimentally showed that it is a valid means for a non-destructive inspection of hidden objects.

In this paper, a simple subcarrier selection combining technique is proposed for orthogonal frequency-division multiplexing (OFDM) systems with multiple receive antennas. The subcarrier-based selection algorithm is developed in the frequency domain to achieve an optimal selection combining gain for OFDM systems, instead of the antenna-based selection algorithms in the time domain or frequency domain. The proposed technique selects an optimal subcarrier with a maximum channel gain among all the receive antennas with the same subcarrier position, based on the estimated channel frequency response during the training period. Hardware complexity for the proposed technique is minimal since it requires single front-end with multiple receive antennas and single baseband demodulator. It is shown by computer simulation that a significant gain can be achieved by the proposed technique over the conventional selection combining technique for OFDM systems in practical situations.

A novel RF CMOS high Q-value active inductor is proposed in this work by using simple cascode RC feedback compensation technique. The performance of this active inductor has maximum Q-value about 1.2E6, inductance value from 3.5 nH to 4.5 nH and 3E-5Ω of minimum total equivalent loss, in the range of 1.2 GHz to 2 GHz.

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.

An optical FM system using an optical FM LD (laser diode) and an optical frequency discriminator (OFD), in which a nonlinear compensation scheme based on the interaction between its nonlinearities can minimize intermodulation distortion. This paper theoretically investigates the minimization influence for 3rd plus 5th order intermodulation distortion power for an optical FM radio-on-fiber system. The carrier to noise-plus-distortion power ratio (CNDR) is theoretically analyzed in employing the OFD whose transmission characteristic is controlled by a phase shifter. The results show that the designed receiver can achieve higher CNDR in the application of multicarrier transmission.

We present low-cost millimeter-wave (MMW) photonic techniques for implementing gigabit/s wireless links. A passive mode-locked laser consisting of a Fabry-Perot laser and a single-mode fiber is used to generate 120-GHz optical MMW signals. We modulated these MMW signals by controlling the bias voltage of the photodiode. The MMW generation and modulation methods do not need expensive photonic components or high-power drivers. A link employing these low-cost photonic techniques achieved 1.25-Gbit/s wireless data transmission.

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.

The fiber-optic sectorized remote antenna system by using the radio frequency (RF) optical transmission technique was promising for increasing the number of subscribers in the millimeter-wave broadband wireless access (MMW BWA) networks. To realize the cost-effectiveness of the fiber-optic sectorized remote antenna system covering four areas, we reached the conclusion that the best multiplexing schemes were the sub-carrier division multiplexing (SCM) of the intermediate frequency (IF) signals of 2 GHz for the down link, the coarse wavelength division multiplexing (CWDM) with the IF signals optical transmission for the up link and 1.3/1.55 µm-WDM for multiplexing the down link and the up link. In addition, the target specifications of this SCM-CWDM system were described, and the designs of the carrier to noise ratio (CNR) and the third order intermodulation distortion (IM3) were examined.

Full-duplex transmission of 60.0 GHz and 59.6 GHz millimeter-wave (mm-wave) signals of 155.52-Mbit/s differential phase shift keying (DPSK) data, radio-on-fiber (ROF) signals over 25-km-long standard single-mode fibers (SMFs) is experimentally demonstrated for the first time using a single 2-RF-port electroabsorption transceiver (EAT). The simplification of base stations (BSs) is strongly required to realize cost-effective and high-reliability mm-wave wireless access. This single EAT detects a C-band ROF signal modulated by a mm-wave downlink signal and simultaneously modulates the L-band optical carrier by a mm-wave uplink signal. The BS mainly consists of the EAT, leading to a simple and low-cost BS. Optical pilot tones and optical bandpass filters are used for photonic downconversion and photonic upconversion, to convert frequencies between mm-wave signals and intermediate frequency (IF) signals in the optical domain. With the use of optical conversions, these signals have no significant fading problems. The simultaneous transmission of both up- and downlinks has been achieved with the BER of less than 10-9. Also the fading problems due to the fiber dispersion of photonic conversions are analyzed mathematically in this paper. The single-EAT BS will become a promising candidate for a ROF access system.

In the problem of determining the major frequency components of a signal disturbed by noise, a model selection criterion has been proposed. In this paper, the criterion has been extended to cover a penalized cost function that yields a componentwise shrinkage estimator, and it exhibited a consistent model selection when the proposed criterion was used. Then, a simple numerical simulation was conducted, and it was found that the proposed criterion with an empirically estimated componentwise shrinkage estimator outperforms the original criterion.

In this paper, we derive spatial correlation functions of linear and circular antenna arrays for three types of angular energy distributions: a Gaussian angle distribution, the angular energy distribution arising from a Gaussian spatial distribution, and uniform angular distribution. The spatial correlation functions are investigated carefully. The spatial correlation is a function of antenna spacing, array geometry and the angular energy distribution. In order to emphasize the research and their applications in diversity reception, as an example, performance of the antenna arrays with MRC in correlated Nakagami fading channels is investigated, in which analytical formulas of average BER for the spatial correlation are obtained.

A low power MPEG-4 video codec LSI with the capability for core profile decoding is presented. A 16-b DSP with a vector pipeline architecture and a 32-b arithmetic unit, eight dedicated hardware engines to accelerate MPEG-4 SP@L1 codec, CP@L1 decoding and post video processing, 20-Mb embedded DRAM, and three peripheral blocks are integrated together on a single chip. MPEG-4 SP@L1 codec, CP@L1 decoding and post video processing are realized with a hybrid architecture consisting of a programmable DSP and dedicated hardware engines at low operating frequency. In order to reduce the power consumption, clock gating technique is fully adopted in each hardware block and embedded DRAM is employed. The chip is implemented using 0.18-µm quad-metal CMOS technology, and its die area is 8.8 mm 8.6 mm. The power consumption is 90 mW at a SP@L1 codec and 110 mW at a CP@L1 decoding.

The coarse frequency offset estimation algorithm has to provide an initial frequency error estimate, which is sufficiently accurate in order to operate reliably for the subsequent fine frequency synchronization algorithm. In this letter, we deal with a coarse frequency offset estimation for digital audio broadcasting. We propose an improved frequency synchronization scheme which uses the minimum energy detection scheme. We compare the performance of proposed scheme with that of conventional schemes under AWGN and Rayleigh channel. It has been shown that the proposed algorithm has high robustness against a large range of symbol timing offset with a low complexity.

A new clock and data recovery circuit (CDR) is realized for the application of data communication systems requiring GHz-range clock signals. The high frequency jitter is one of major performance-limiting factors in CDR, particularly when NRZ data patterns are used. A novel phase detector is able to suppress this noise, and stable clock generation is achieved. Furthermore, optical characteristics for fast locking are achieved with the adaptive delay cell in the phase detector. The circuit is designed based on CMOS 0.25 µm fabrication process and its performance is verified by measurement results.

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.

This letter presents the implementation results of an application-level cache file system, MCFS, which is specifically designed to provide efficient caching and transmission mechanisms for streaming media. The file system is built on a virtual file disk which is constructed as a single large file on a general-purpose file system. MCFS suits the access requirement of continuous media caching and provides an efficient I/O mechanism for cache servers. The experimental results show that MCFS outperforms the comparison model and provides a consistent I/O bandwidth.

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.

Detection efficiency and dark count of a Geiger mode single photon detection avalanche photodiode was studied by a numerical simulation. The ionization process triggered by a single hole injection was simulated at a bias voltage slightly greater than the avalanche breakdown voltage for calculation of the detection efficiency. Tunneling effect in the multiplication layer was taken into account for the dark count simulation. In the gated-mode operation, the avalanche build-up time also affects on the signal to noise ratio. The multiplication layer thickness is a key parameter for the device performances.

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.

The design of the analog part of a mixed analog-digital IC for a commercial wireless burglar alarm system is presented as an example of a very low-power VLSI design for battery-operated systems. The main constraint is battery life, which must be at least five years (with standard camera-battery). An operational amplifier, a power supply monitor and an oscillator are the core of the design. The operational amplifier absorbs 1.5 µA while the entire analog part absorbs 4 µA. Measures on each single part show compliance with specification. Test on working environment show its full functionality. Even though the example is application specific, the design solutions and each single element can also be utilized in many other battery-operated low-frequency devices (e.g. environmental parameter monitoring).