Study of the Formation Mechanism of Cu/Ge/Pd Ohmic Contact to <Emphasis Type="Italic">n</Emphasis>-Type InGaAs

This study investigates electrical characteristics and the formation mechanism of the Cu/Ge/Pd Ohmic contact to n-type InGaAs. After annealing the contact at 250°C for 20 min, Cu₃Ge and Pd₁₂Ga₅As₂ compounds formed and Ge diffused into the InGaAs layer, achieving a heavily doped InGaAs layer with a low contact resistivity of 1 × 10⁻⁶ Ω cm². Thermal stability tests were performed on the Cu/Ge/Pd Ohmic contact to InGaAs after Ohmic contact formation, showing no obvious degradation after a 72 h reliability test at 250°C. The results indicate excellent electrical characteristics and thermal stability using Cu/Ge/Pd as an Ohmic contact metal to an n-InGaAs layer.     

Novel dual-frequency and broad-band designs of slot-loadedequilateral triangular microstrip antennas

By loading properly arranged slots in an equilateral-triangular microstrip patch, novel dual-frequency and broad-band operations of a single-feed triangular microstrip antenna are presented. For dual-frequency operation, the proposed design is achieved by loading two pairs of narrow slots in the triangular patch, one embedded close to the side edges of the patch and the other inserted at the bottom edge of the patch. The obtained two operating frequencies are of same polarization planes and by varying the positions and lengths of the inserted slots at the bottom edge of the patch, a tunable frequency ratio of the two frequencies ranging from about 1.16 to 2.06 is obtained. Furthermore, it is found that by protruding a narrow slot out of the embedded slots close to the side edges, broad-band operation of the triangular microstrip antenna near its fundamental resonant mode can be achieved. Results show that the antenna bandwidth of the proposed broad-band design can be greater than 2.6 times that of a conventional triangular microstrip antenna. Details of the proposed dual-frequency and broad-band designs are described and typical experimental results are presented and discussed     

Investigation of candidate VRM topologies for futuremicroprocessors

By reducing the power supply voltage, faster, lower power consumption, and high integration density data processing systems can be achieved. The current generation high-speed complementary metal-oxide-semiconductor (CMOS) processors (e.g., Alpha, Pentium, Power PC) are operating at above 300 MHz with 2.5 to 3.3 V output range. Future processors will be designed in the 1.1-1.8 V range, to further enhance their speed-power performance. These new generation microprocessors will present very dynamic loads with high current slew rates during transient. As a result, they will require a special power supply, voltage regulator module (VRM), to provide well-regulated voltage. The VRMs should have high power densities, high efficiencies, and good transient performance. In this paper, the critical technical issues to achieve this target for future generation microprocessors are addressed. A VRM candidate topology, interleaved quasisquare-wave (QSW), is proposed. The design, simulation and experimental results are presented     

Phase-matched four-wave mixing between pumps and signals in a copumped Raman amplifier

We observe four-wave mixing (FWM) between copropagating pumps and signals in a Raman amplifier when the zero-dispersion wavelength of the transmission fiber lies symmetrically between the pump and the signal wavelengths. The resultant FWM products, which grow as they experience Raman gain along the fiber, can degrade the signal's optical signal-to-noise ratio by as much as 10 dB for a Raman ON-OFF gain of 15 dB.     

Encrypted image classification based on multilayer extreme learning machine

Nowadays, numerous corporations (such as Google, Baidu, etc.) require an efficient and effective search algorithm to crawl out the images with queried objects from databases. Moreover, privacy protection is a significant issue such that confidential images must be encrypted in corporations. Nevertheless, decrypting and then classifying millions of encrypted images becomes a heavy burden to computation. In this paper, we proposed an encrypted image classification framework based on multi-layer extreme learning machine that is able to directly classify encrypted images without decryption. Experiments were conducted on popular handwritten digits and letters databases. Results demonstrate that the proposed framework is secure, efficient and accurate for classifying encrypted images.     

Adaptive antennas at the mobile and base stations in an OFDM/TDMAsystem

Several smart antenna systems have been proposed and demonstrated at the base station (BS) of wireless communications systems, and these have shown that significant system performance improvement is possible. We consider the use of adaptive antennas at the BS and mobile stations (MS), operating jointly, in combination with orthogonal frequency-division multiplexing. The advantages of the proposed system includes reductions in average error probability and increases in capacity compared to conventional systems. Multiuser access, in space, time, and through subcarriers, is also possible and expressions for the exact joint optimal antenna weights at the BS and MS under cochannel interference conditions for fading channels are derived. To demonstrate the potential of our proposed system, analytical along with Monte Carlo simulation results are provided     

Serial communication circuit with optimized skew characteristics

This letter highlights features of an optimized serial communication system, including an oversampling technique of data recovery, issues related to off-board communications and a modified universal asynchronous receiver transmitter (UART) implemented in a programmable logic device (PLD). The resulting system provides high skew tolerance at 44 Mb/s data rate and has achieved a transmission distance of 130 m, at this rate, with the aid of an enhanced differential transceiver circuit. The principal application is for embedded systems with medium distance communication requirements. This UART can be integrated with other communication functions, such as packet routing switches, in a PLD device     

Minimizing hydrogen content in silicon oxynitride by thermal oxidation of silicon-rich silicon nitride

This work reports a detailed study of the re-oxidation effects on the hydrogen content and optical properties of silicon oxynitride films grown by plasma enhanced chemical vapor deposition (PECVD) with N₂O, NH₃ and SiH₄ as the precursors. Results showed that the silicon oxynitride deposited with gas flow rates of NH₃/N₂O/SiH₄ = 20/500/20 (sccm) has favorable properties for integrated waveguide applications. The refractive index of this layer is about 1.57 at 632.8 nm wavelength and the layer has a comparative low density of NH bonds. With a high temperature re-oxidation of the as-deposited film, the hydrogen content of the oxynitride film was reduced from 2.255 × 10²² to 6.98 × 10²⁰ cm⁻³ which is attributed to the removal of excess silicon oxidation and hydrogen bonds.     

Multi-objective module placement for 3-D system-on-package

System-on-package (SOP) is a viable alternative to system-on-chip (SOC) for meeting the rigorous requirements of today's mixed-signal system integration. Thermal integrity is arguably the most crucial issue in three-dimensional (3-D) SOP due to the compact nature of the 3-D integration. In addition, the power supply noise issue becomes more serious as the supply voltage continues to decrease while the number of active devices consuming power increases. We propose a 3-D module and decap (decoupling capacitance) placement algorithm that evenly distributes the thermal profile and reduces the power supply noise. In addition, we allocate white spaces around the modules that require decaps to suppress the power supply noise while minimizing the area overhead. In our experimentation, we achieve improvements in both maximum temperature and decap amount with only small increase in area, wirelength, and runtime.     

Fast-polarization-hopping transmission diversity to mitigate prolonged deep fades in indoor wireless communications

Fast-polarization-hopping (FPH) transmission diversity is herein proposed to mitigate prolonged deep fades at the mobile receiver in, for example, the indoor propagation environment. Even if the individual multipaths are each sufficiently strong for detection, deep fades may occur due to the multipath signals' destructive summation at the receiver. The relative immobility of the transmitter, the propagation environment, and the receiver in the indoor environment means that a deep fade may last for a very long duration, dropping calls or severing links. By rapidly hopping the transmission polarization (say, alternating transmission between a vertically-polarized-dipole antenna and a horizontally-polarized-dipole antenna - or between two "X"-oriented dipoles), the effective propagation channel experiences consecutive polarization modes (each involving a different multipath summation), all within the duration allowed by the channel-coder's interleaving depth. This scheme is usable for either frequency-shift keying (with incoherent demodulation), or for channel-coded phase-shift keying (with differential coding, or with pilot-symbol phase synchronization). This scheme requires no change in the mobile receiver (which does not need to be dual polarized). The base station also needs no spatially separated antenna array, nor any other additional hardware, no mechanical movement of the transmitting antenna(s), and no sophisticated signal processing (such as channel estimation or closed-loop feedback) nor any additional software. The proposed scheme's cost - relative to using antenna arrays at the base station and/or the mobile - is a potentially doubling of the transmission bandwidth. The proposed scheme's potential is illustrated by limited computer simulations using CINDOOR, a polarization-sensitive indoor wireless-propagation ray-tracing simulation software package based on geometrical optics and the uniform theory of diffraction (GO/UTD).