Robust Space Time Receiver for CDMA-based Antenna Arrays

In this paper, we propose a new robust code division multiple access (CDMA) receiver of which weight vector is obtained by projecting the effective spatio-temporal signature waveform onto the signal subspace of the data covariance matrix. We verified our proposed algorithm by the field measured data obtained with a custom-built wideband CDMA test-bed. It will be shown that the proposed algorithm is robust to the signal mismatch.     

A 15 nm Ultra‐thin Body SOI CMOS Device' with Double Raised Source/Drain for 90 nm Analog Applications

Fully‐depleted silicon‐on‐insulator (FD‐SOI) devices with a 15 nm SOI layer thickness and 60 nm gate lengths for analog applications have been investigated. The Si selective epitaxial growth (SEG) process was well optimized. Both the singleraised (SR) and double‐raised (DR) source/drain (S/D) processes have been studied to reduce parasitic series resistance and improve device performance. For the DR S/D process, the saturation currents of both NMOS and PMOS are improved by 8 and 18%, respectively, compared with the SR S/D process. The self‐heating effect is evaluated for both body contact and body floating SOI devices. The body contact transistor shows a reduced self‐heating ratio, compared with the body floating transistor. The static noise margin of an SOI device with a 1.1 µm² 6T‐SRAM cell is 190 mV, and the ring oscillator speed is improved by 25 % compared with bulk devices. The DR S/D process shows a higher open loop voltage gain than the SR S/D process. A 15 nm ultra‐thin body (UTB) SOI device with a DR S/D process shows the same level of noise characteristics at both the body contact and body floating transistors. Also, we observed that noise characteristics of a 15 nm UTB SOI device are comparable to those of bulk Si devices.     

Error Concealment Based on Semantic Prioritization with Hardware‐Based Face Tracking

With video compression standards such as MPEG‐4, a transmission error happens in a video‐packet basis, rather than in a macroblock basis. In this context, we propose a semantic error prioritization method that determines the size of a video packet based on the importance of its contents. A video packet length is made to be short for an important area such as a facial area in order to reduce the possibility of error accumulation. To facilitate the semantic error prioritization, an efficient hardware algorithm for face tracking is proposed. The increase of hardware complexity is minimal because a motion estimation engine is efficiently re‐used for face tracking. Experimental results demonstrate that the facial area is well protected with the proposed scheme.     

Performance of GaAs-AlGaAs V-grooved inner stripe quantum-well wirelasers with different current blocking configurations

GaAs-AlGaAs V-grooved inner stripe (VIS) quantum-well wire (QWW) lasers grown by metalorganic chemical vapor deposition with different current blocking configurations, n-blocking on p-substrate (VIPS), p-n-p-n blocking on n-substrate (VI(PN)_nS) and p-blocking on n-substrate (VINS) have been fabricated and characterized. The VIPS QWW lasers show the most stable characteristics with effective current confinement: one of the lasers shows fundamental transverse mode, lasing up to 5 mW/facet, typical threshold current of 39.9 mA at 818.5 mm, an external differential quantum efficiency of 24%/facet, and characteristic temperature of 92 K. The current tuning rate was almost linear at 0.031 mm/mA, and the temperature tuning rate was measured to be 0.14 nm/°C. Comparison of the light output versus current characteristics of the lasers with different current blocking configurations is presented here     

Asymmetric X-junction thermooptic switches based on fluorinatedpolymer waveguides

Thermooptic 2×2 switches based on low-loss fluorinated polymer waveguides have been demonstrated. For the waveguide possessing a low-loss around the 1.55-μm wavelength, crosslinkable fluorinated poly(arylene ethers) (FPAE) is developed as a core material and perfluorocyclobutane (PFCB) is used as a cladding material. To enhance the fabrication tolerance and to achieve a low switching power, asymmetric X-junctions with a Mach-Zehnder interferometer are exploited for the polymeric waveguide switches. An inverted rib waveguide structure is fabricated by filling up the etched groove on a lower cladding with the core polymer. The switch exhibits a crosstalk of less than -20 dB, a switching power of 10 mW, and an insertion loss of 4.5 dB     

The Evolution of Korean Information Infrastructure and Its Future Direction: A System Dynamics Model

The recent technological and industrial revolution dictates a new approach in constructing Korean Information Infrastructure. Lacking past data on the newly emerging markets, econometrics methodologies cannot accurately forecast future paths of advanced networks, let alone dynamic impacts of public policies. In this paper, we have built a system dynamics model of the Korean Information Infrastructure and simulated diverse policy measures including market integration and government initiative in investment for experimenting their effectiveness. The most counterintuitive result of our research is that the market integration policy will facilitate CATV networks at an early stage until the year 2010, but will result in a diminished market size in the long run. With the system dynamics approach, we can enhance our understanding of the complex policy systems and get valuable insights through learning by modeling and simulation.     

Interdiffusion behavior of Hg in HgTe/CdTe superlattices grown on Cd0.96Zn0.04 Te (211)B substrates by molecular beam epitaxy

Double-crystal x-ray rocking curve (DCRC) and secondary-ion mass-spectroscopy (SIMS) measurements have been performed to investigate the effect of rapid thermal annealing on the interdiffusion behavior of Hg in HgTe/CdTe superlattices grown on Cd_0.96Zn_0.04Te (211)B substrates by molecular beam epitaxy. The sharp satellite peaks of the DCRC measurements on a 100-period HgTe/CdTe (100Å/100Å) superlattice show a periodic arrangement of the superlattice with high-quality interfaces. The negative direction of the entropy change obtained from the diffusion coefficients as a function of the reciprocal of the temperature after RTA indicates that the Hg diffusion for the annealed HgTe/CdTe superlattice is caused by an interstitial mechanism. The Cd and the Hg concentration profiles near the annealed HgTe/CdTe superlattice interfaces, as measured by SIMS, show a nonlinear behavior for Hg, originating from the interstitial diffusion mechanism of the Hg composition. These results indicate that a nonlinear interdiffusion behavior is dominant for HgTe/CdTe superlattices annealed at 190°C and that the rectangular shape of HgTe/CdTe superlattices may change to a parabolic shape because of the intermixing of Hg and Cd due to the thermal treatment.     

A comparison of two micromachined inductors (bar- and meander-type)for fully integrated boost DC/DC power converters

Two micromachined integrated inductors (bar- and meander-type) are realized on a silicon wafer by using modified, IC-compatible, multilevel metallization techniques. Efforts are made to minimize both the coil resistance and the magnetic reluctance by using thick electroplated conductors, cores, and vias. In the bar-type inductor, a 25-μm thick nickel-iron permalloy magnetic core bar is wrapped with 30-μm thick multilevel copper conductor lines. For an inductor size of 4 mm×1.0 mm×110 μm thickness having 33 turns of multilevel coils, the achieved specific inductance is approximately 30 nH/mm² at 1 MHz. In the meander-type inductor, the roles of conductor wire and magnetic core are switched, i.e., a magnetic core is wrapped around a conductor wire. This inductor size is 4 mm×1.0 mm×130 μm and consists of 30 turns of a 35-μm thick nickel-iron permalloy magnetic core around a 10-μm thick sputtered aluminum conductor lines. A specific inductance of 35 nH/mm² is achieved at a frequency of 1 MHz. Using these two inductors, switched DC/DC boost converters are demonstrated in a hybrid fashion. The obtained maximum output voltage is approximately double an input voltage of 3 V at switching frequencies of 300 kHz and a duty cycle of 50% for both inductors, demonstrating the usefulness of these integrated planar inductors     

Thermally robust Ta2O5 capacitor for the256-Mbit DRAM

The thermal degradation of the Ta₂ O₅ capacitor during BPSG reflow has been studied. The cause of deterioration of Ta₂O₅ with the TiN top electrode was found to be the oxidation of TiN. By placing a poly-Si layer between TiN and BPSG to suppress oxidation, the low leakage current level was maintained after BPSG reflow at 850°C. The Ta₂O₅ capacitor with the TiN/poly-Si top electrode was integrated into 256-Mbit DRAM cells and excellent leakage current characteristics were obtained     

Integrated optical high-voltage sensor based on a polymeric Y-branch digital optical switch

An integrated optical high-voltage sensor is realized by fabricating a Y-branch digital optical switch in an electrooptic polymer. The measurement of ac high voltage is accomplished by using the linear transfer characteristics of the switch at zero bias voltage. Furthermore, the logarithmic ratio between the optical powers of two output ports may be used to remove the noise caused by the power fluctuations of a light source. The polymeric high-voltage sensor requires no electrical dc biases and no voltage dividers. It is also wavelength insensitive and fabrication-tolerant due to its use of mode evolution effects instead of interference. The measured sensing voltage range is as large as ac 500-V peak-to-peak.