A new type of compact one dimension (1-D) microstrip photonic bandgap (PBG) structure for filter is presented. A miniature semiconductor-based structure band-stop filter with four cells is simulated, fabricated, and measured. Agreement between the experimental and simulation results has been achieved. The filter with four proposed PBG structure exhibits deep (about -60 dB) and steep (about 40 dB/GHz) stop-band characteristics. It also has less loss and ripples in the pass-band. The period of the PBG lattice is about 0.2 λe (λe, guiding wavelength at the center frequency of stop-band), or 0.068 λ0 (λ0 wavelength in air), and the filter is very compact and much easier for fabrication and realization in MIC and MMIC.

It is shown that bounded impulse action can be combined with usual bang-bang control input to minimize the performance index. Especially for unstable oscillators, the size of controllable region can be increased. We present results on how to minimize the performance index using both ordinary bang-bang control and impulse actions with a recharge constraint on impulse firing. Following the maximum principle and necessary conditions induced from usual perturbation arguments, the mixed control input (bang-bang and impulse actions) is represented in adjoint state and then state variable feedback form. Simulation results show how the switch curves can be used to determine the optimal control value.

A novel class of time-varying subband transforms and its application in image coding are introduced. We construct the framework in which an analysis subband transform is chosen from a given set of analysis transforms and perfect reconstruction is achieved. To this end, we suggest the reconstruction method from the transformed coefficients by applying the theory of convex projections (POCS). We introduce convex sets for perfect reconstruction from the transformed vector. We further propose other convex sets which assure smoothness of plane regions for image coding applications. We show several image coding examples. The proposed coding method is an extension of conventional one with multiple block-based transforms. At each time instance (block), the transform to be applied is chosen from a given set of orthogonal subband transforms according to a certain criterion. Experimental results show that the use of multiple subband transforms leads to the improvement of coding performance compared to the use of single transform even though there exists side information.

In this paper we describe the investigation of design methodology of a planar duplexer consisting of BPFs using mixed tapped resonators. Firstly, we propose the planar duplexer consisting of bandpass filters (BPFs) using a tapped open-ended λ/2 resonator and a tapped λ/4 resonator. The duplexer is designed based on the general filter theory with narrow band approximation and tap-coupling technique. The actual duplexer is fabricated using a coplanar waveguide (CPW). Secondly, downsizing of the planar duplexer is carried out based on the BPF using stepped impedance resonators (SIRs). Lastly, another type of duplexer consisting of different BPFs using mixed tapped resonators is investigated in the same manner. The results of this study lead us to the conclusion that the design methodology is useful for realizing the high-performance planar duplexer fabricated without increasing the number of elements.

The authors have established new switching architecture of all optical WDM network suitable for the application of video transmission. In this paper, emphasis is put on a setup of a wavelength connection based on contiguous wave-band pool and we have proposed new Wave-Band Routing and Assignment (WBRA) method which provides simple switching and high speed wavelength assignment. Assuming the environment without wavelength convertor, our wave-band switching scheme is applied to several network topologies for performance evaluation. Then effectiveness and feasibility of this scheme are confirmed from a viewpoint of the number of required wavelengths. Simulation results indicate that our proposal scheme attains lower number of required wavelengths as compared to the fixed wave-band scheme. Assuming to use wavelength convertors, we have also evaluated the situation that the number of hops is restricted.

In this paper a digital frequency domain RFI (Radio Frequency Interference) cancellation scheme for DMT (Discrete Multitone) based VDSL (Very high speed Digital Subscriber Line) systems is presented. The proposed algorithm has been optimized and characterized in terms of complexity and performance. Optimizations were also performed from an implementation point of view by deducing key dependencies among our RFI model coefficients that let us drastically reduce the size of the memories involved. System simulations showed the effectiveness of the canceller: in terms of VDSL performance parameters such as bit rate, the optimized cancellation scheme recovers almost totally the performance degradation due to RFI.

In this paper, we first address the current state of broadband services in Korea. Here, we introduce relevant statistics, current access network architectures, and activities of some major carriers. We also briefly introduce Korean government's policies on research and development projects and plans for promoting the country toward an advanced information society. We then introduce a large-scale, collaborative project named "Photonic Access To the Home (PATH)" with five-year period of performance, started in year 2002. The project is under leadership of the government and ETRI in collaboration with universities and industry. We finally provide a rather detailed description of the FTTH (Fiber To The Home) technology based on the wavelength division multiplexing technology, which has been under research in our laboratory as a part of the PATH project. We show some of our achievement including new architectures and networking principles for the FTTH network, analysis of the dynamic allocation of user bandwidth, and the experiment for a low-cost WDM optical source.

We propose a hierarchical cross-connect node employing tunable waveband aggregators on the internal links. In a square grid network, the number of the switch ports for the internal links is reduced by 40 to 60% when the number of nodes is 50.

This paper presents an advanced quad-band multi-chip power amplifier module with unique linear output power dependency to the control voltage. It was developed for GSM850/900 MHz and DCS1800/PCS1900 MHz handset applications. The module was made on 10 mm by 10 mm substrate, which combined an InGaP HBT GSM, and DCS power amplifier ICs, two integrated couplers, a dual-band logarithmic RF power detector and some additional passive components. The logarithmic RF power detector was implemented in the module using state-of-the-art Si technology to accomplish the linear power dependency. With the logarithmic RF power detector approach we achieved more than 50 dB linear output power control range. The output power in dBm is a linear function of a control voltage; therefore there is no need for the Original Equipment Manufacture to design a power control circuitry. This is a very desirable feature to many handset designers who want to significantly reduce the handset board size, design cost, and time-to-market. The approach allows the handset manufacturer to calibrate the output power at two points with error of less than 0.3 dB, thus significantly reducing test time in mass production. Under a low single supply voltage of 3.2 V the module provides 35 dBm output power, 55% PAE in GSM900 band and 33 dBm, 50% PAE in DCS1800 band.

This paper first presents an active integrated antenna configuration designed for broadband mobile wireless access systems using the 25-GHz band. This active integrated antenna comprises a microstrip antenna array and RF front-end circuits adopting spatial power combining schemes for reduced power consumption of the power amplifiers. Furthermore, the antenna and RF circuits are integrated into each side of a thick copper backing plate and both are connected through microstrip line /slot transitions. The developed active integrated antenna achieves the output power of 14.6 dBm and a noise figure of less than 5 dB. The wireless system using the developed active integrated antenna achieves a 6-dB improvement in the packet error rate compared to that using a passive antenna with the same array design as the active integrated antenna. Furthermore, we obtained the first license of the active integrated antenna for commercial use in high-speed wireless communication systems in Japan.

A compact high-temperature superconducting (HTS) bandpass filter (BPF) using coplanar waveguide (CPW) meander-line parallel-circuited resonators is proposed for microwave receiver applications. The design theory is presented based on a conventional filter theory with J-inverters. Also, analytical and numerical studies of the meander-line resonator are carried out in terms of equivalent circuit values, the resonant frequency, and the unloaded Q. Two- and four-stage 0.05 dB ripple Chebyshev BPFs at 2 GHz with relative bandwidth 60 MHz are fabricated with the metalorganic deposition (MOD)-derived YBCO films on LaAlO3 substrates and their performance are demonstrated. The measured frequency characteristics and the unloaded quality factors agree well with the theoretical and numerical results and the validity of the design theory is confirmed.

A novel periodic element for the sandwich photonic bandgap (PBG) structure named as H-shape element is presented in this paper. Sandwich PBG structure is a kind of PBG structure whose periodic lattice is buried in the midmost of the substrate. There's no requirement to drill or suspend the substrate. The new H-shape element is made of a central block connected with a long and narrow block on either side, and possesses a quite deep forbidden gap, whose width and depth can be tuned by varying the dimension of the central block. Theoretical results, as confirmed experimentally, indicate that the maximum insertion loss in the stopband is up to 80 dB. This sandwich microstrip structure can be constructed using conventional printed-circuit-board fabrication processes and integrated with other microwave components in a multilayered circuit. An improved notch filter with chirped central blocks is presented. The length of the filter is reduced by 16.7%, and the fractional bandwidth is increased by 8.1% compared with that of a conventional sandwich microstrip notch filter on the same substrate. The experimental results agree well with the finite difference time domain (FDTD) simulations.

10-Gbit/s wireless data transmission using 120-GHz millimeter-wave (MMW) photonic technologies is presented. For such high-data-rate transmission, we have newly developed a planar broadband receiver that employs a > 200-GHz Schottky diode and a slot-ring antenna with a 10-dB bandwidth of 30 GHz. The receiver achieves a high video sensitivity of 190 mV/mW at 120 GHz due to its optimized data output circuit. The MMW wireless link using the receiver and photonic transmitter has data transmission bandwidth of 8.5 GHz, and succeeded in 10-Gbit/s data transmission, which is the fastest ever achieved through a MMW wireless link.

The tectonic activities that precede significant earthquakes release electromagnetic (EM) waves that can be used as earthquake precursors. We have been observing EM radiation in the ELF (extremely low frequency) band at about 40 observation stations in Japan for predicting significant earthquakes. The recorded signals contain, however, several noise components generated from the ionosphere, human activity, and so on. Most background noise in observed signal is attributed to lightning in the tropics. This paper proposes method based on PCA (principal component analysis) to extract signals from large data sets. The good performance of the proposed method is confirmed.

A new method for blind watermarking based on quantization is proposed. The proposed scheme embeds a watermark on the lowest wavelet subband in order to be robust. Experimental results demonstrate the robustness of the algorithm against compression and other image processing attacks.

Microstrip antennas on various Uniplane Compact Photonic BandGap (UC-PBG) substrates are investigated. Particularly, anisotropic characteristics of UC-PBG is studied and applied to the design of microstrip diplexer antennas. Moreover, an Embedded UC-PBG (EUC-PBG) scheme is presented to overcome the strong backward radiation caused by the conventional UC-PBG antennas. Such antennas demonstrate the improved radiation properties over the conventional UC-PBG antennas, and the evidence on surface wave suppression is also demonstrated. Experimental results show very good agreement with theoretical predictions.

The authors propose a circular polarization generator using a square waveguide with L-type probe located on a side wall of waveguide. The sides of the L-probe forming the right angle are placed perpendicular to the direction of propagation. The position of the right angle is kept at a distance of a quarter-wave length from the side wall. The device provides 27% bandwidth for 3 dB axial ratio at 8.4 GHz on azimuth interval of 160.

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.

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.

Radio on fiber transmission technique using a conventional intermediate frequency (IF)-band Surface Acoustic Wave (SAW) filter has been proposed in order to satisfy the 3rd Generation Partnership Project (3GPP) specification for International Mobile Telecommunications-2000 (IMT-2000) cellular systems. For the 3GPP specification, a key issue is to expand the dynamic range limited by clipping distortion of laser diode. In order to expand the dynamic range, for the down link, a narrow bandpass SAW filter is introduced after optical transmission, because the SAW filter can suppress the distortion caused by clipping of laser diode and improve the performance of adjacent channel leakage power ratio. For the up link, an optical modulation index (OMI) of a laser diode is optimized to improve the noise figure (NF) performance by controlling the gain of an amplifier between the antenna and the laser diode. As a result, both power control dynamic range of more than 44 dB in the down link and dynamic range of more than 97 dB in the up link were achieved in 6 km optical transmission. Other important parameters, such as Error Vector Magnitude, Reference Sensitivity Level, and so on in the 3GPP specification, were also satisfied.