Tunable wavelength conversion in a semiconductor-fiber ring laser

A tunable wavelength converter is demonstrated using highly nondegenerate four-wave mixing in a semiconductor-fiber ring cavity with no external pump light and low input signal power requirements. This device allows continuous tuning of both pump and converted wavelengths over the semiconductor optical amplifier gain bandwidth. Results for 11.8-nm down- and 6.9-nm up-wavelength conversion with input signal power as low as -10 dBm have been obtained at 1 Gb/s with less than 1.6-dB power penalty     

Wavelet Neural Network Approach for Testing of Switched-Current Circuits

Combining the time and frequency location and multiple-scale analysis of wavelet transform with the nonlinear mapping and generalizing of neural network, an efficient defect-oriented parametric test method using Wavelet Neural Network (WNN) for switched-current integrated circuits is proposed. Contraposing to the fully compatible digital CMOS technology and current scaling calculation of SI circuits, parameter cohort of switched current elements is used to compute the sensitivity and gain tolerance and is applied for selecting the test models. The selecting of the appropriate wavelet function based on particular switched current fault signal is discussed, and the number of network input and output nodes are determined by the circuit status and dimension of eigenvector which is the energy of wavelet decomposition coefficient. To simplify configuration of the neural network, the sampled data was preprocessed by wavelet transform. Illustrative examples show that the proposed wavelet neural network method for testing of switched current circuits is effective.     

LDPC code design for asynchronous Slepian-Wolf coding

We consider asynchronous Slepian-Wolf coding where the two encoders may not have completely accurate timing information to synchronize their individual block code boundaries, and propose LDPC code design in this scenario. A new information-theoretic coding scheme based on source splitting is provided, which can achieve the entire asynchronous Slepian-Wolf rate region. Unlike existing methods based on source splitting, the proposed scheme does not require common randomness at the encoder and the decoder, or the construction of super-letter from several individual symbols. We then design LDPC codes based on this new scheme, by applying the recently discovered source-channel code correspondence. Experimental results validate the effectiveness of the proposed method.     

Unambiguous sine-phased binary offset carrier modulated signal acquisition technique

In this letter, a side-peak cancelation unambiguous acquisition technique is proposed for sine-phased binary offset carrier (BOC) modulated signals. The test criterion used in this technique is based on a synthesized correlation function which has no major positive side peak. This synthesized correlation function is obtained by subtracting the cross-correlation between the received sin-BOC signal and an auxiliary signal from the autocorrelation of sin-BOC signal. For different types of BOC signal, the proposed technique employs corresponding modulated symbols of the auxiliary signal. The common solution of the symbol shape vector is derived, and the theoretical false alarm and detection performance formulas are given. Theoretical and simulation results show that at the expense of some performance degradation this technique completely removes the ambiguity threat in acquisition process.     

Opportunistic decoding of unequal erasure protected scalable coded source

In this paper,we propose an opportunistic decoding method to enhance the reconstruction of unequal erasure protected scalable coded source.This method explores some non-channel-decodable symbols of the received packets by opportunistically utilizing the structure information of joint source-channel coding scheme.As a result,a longer prefix of source coded stream may be obtained to enhance the reconstruction of scalable coded source.Experiment results indicate that opportunistic decoding at the receiver can ...     

Surface-tension measurements of the eutectic alloy (Ag-Sn 96.2 at.%) with Cu additions

The maximum bubble-pressure method has been used to measure the surface tension and density of liquid alloys (Ag-Sn)_eut + Cu (X_Cu = 0.005, 0.020, 0.0375, and 0.065 (mole fraction)). The surface tension and density measurements were curried out in the temperature ranges of 262–942°C and 264–937°C, respectively. The linear dependencies of surface tensions and densities on temperature were observed, and they were described by straight-line equations. It has been found that the additions of Cu to the Ag-Sn eutectic alloy increase the surface tension. Experimental data of the surface tension were compared with those from modeling based on Butler’s method, using the optimized-thermodynamic parameters from the literature, and a slight tendency contrary to the experimental results was observed.     

Time-resolved photoluminescence of polycrystalline GaN layers on metal substrates

The low-temperature time-resolved photoluminescence of polycrystalline GaN layers grown by molecular beam epitaxy on metal substrates (Mo and Ta) was investigated. The photoluminescence spectra observed include two emission bands in the ultraviolet spectral region. We assign one of these bands to recombination processes inside cubic nanocrystallites, which are formed in the hexagonal polycrystalline GaN host. The recombination radiation of cubic nanocrystallites is enhanced due to predominant trapping of the nonequilibrium electron-hole pairs in these crystallites.     

Power aware channel width tapering of serially connected MOSFETs

This paper reviews a transistor channel width tapering scheme called Hill Tapering for FET chains with specific emphasis on power dissipation and layout area of the tapered chains. The Hill Tapering scheme results in the lowest power dissipation and physical area compared to any of the existing tapering schemes like linear, exponential or optimal tapering. It also offers high speed operation. This tapering scheme is general and suits domino logic circuit designs. SPICE simulation results have shown that up to 81% power dissipation reduction could be achieved by using this tapering scheme.     

Joint Carrier Frequency Offset Estimation and Compensation for Downlink Group-Orthogonal Multicarrier CDMA

A carrier frequency offset (CFO) estimation and compensation method is proposal for downlink group-orthogonal multicarrier code-division multiple-access (GO-MC-CDMA) system. The proposed algorithm has taken into consideration both the inherent orthogonality among subcarriers of different groups of GO-MC-CDMA system and the characteristics of Fast Fourier Transform (FFT) demodulation are taken into consideration. The CFO estimation is achieved by searching the value which minimizes the cost function constructed in terms of performing FFT on the interfering signals. Simulation results show that the estimated value of CFO is very close to the real value for the downlink GO-MC-CDMA system. In addition, it is shown that the bit error rate (BER) performance is improved significantly by CFO compensation.