Results of the Enumeration of Costas Arrays of Order $27$

This correspondence presents the results of the enumeration of Costas arrays of order $27$: all arrays found, except for one, are accounted for by the Golomb and Welch construction methods.      

Algebraic Decoding of the $(89, 45, 17)$ Quadratic Residue Code

Recently, an algebraic decoding algorithm suggested by Truong (2005) for some quadratic residue codes with irreducible generating polynomials has been designed that uses the inverse-free Berlekamp–Massey (BM) algorithm to determine the error-locator polynomial. In this paper, based on the ideas of the algorithm mentioned above, an algebraic decoder for the $(89, 45, 17)$ binary quadratic residue code, the last one not decoded yet of length less than $100$ , is proposed. It was also verified theoretically for all error patterns within the error-correcting capacity of the code. Moreover, the verification method developed in this paper can be extended for all cyclic codes without checking all error patterns by computer simulations.      

General Error Locator Polynomials for Binary Cyclic Codes With $t le 2$ and $n < 63$

In this paper, we show that a recently proposed algorithm for decoding cyclic codes may be applied efficiently to all binary cyclic codes with tles2 and n<63. This is accomplished by providing structure theorems for the codes in this range and classifying the relevant cases     

Opening of Hybrid Bandgaps in Two-Dimensional Photonic Crystals of Pb(Mg$_{1/3}$Nb$_{1/3}$ )O$_{3}$–PbTiO $_{3}$ Having Very Low Refractive Index Contrast

The effect of anisotropy on two-dimensional photonic crystals of hexagonally arranged Pb(Mg_1/3Nb_1/3)O₃-PbTiO₃ (PMNT) rods in air background was analyzed using a finite-difference time-domain method. The refractive index contrast between PMNT (n = 2.47) and air is low compared to conventional semiconductor-air photonic crystals. Yet, hybrid (polarization-independent) photonic bandgaps were achieved for anisotropic PMNT rods by adjusting the structural parameters and the anisotropy. The maximum bandwidth found was 20 nm. It was possible to engineer the center wavelength of this bandgap to 980, 1300, and 1550 nm, for potential applications as switches, electrooptic filters, and modulators in this region.     

Linear Retro-Directive Antenna Array Using 90$^{circ}$ Hybrids

A novel approach is developed to design linear passive retro-directive antenna arrays by properly making use of 90deg hybrids. For a 90deg hybrid, when its direct port and coupled port are terminated with the same reflection coefficient, the phase difference of the reflected signals at the other two ports are reversed to that of the incident signals. This then becomes to be a phase difference reversal circuit (or a retro-directive circuit) and leads to the design of linear retro-directive antenna arrays using 90deg hybrids. The formulas and a folding method on designing linear retro-directive array circuits with arbitrary element numbers are presented with the measurement results of three-element, four-element, and six-element retro-directive antenna arrays.     

Ytterbium-Doped P$_2$O$_5$-TeO $_2$ Glass for Laser Applications

Ytterbium-doped sodium phospho-tellurite glasses are made with different P₂O₅:TeO₂ ratio, and Yb³⁺ concentrations. Physical properties of the new Yb hosts are favorable for laser applications. The glasses show high absorption and emission cross sections and higher lifetime of Yb³⁺:²F_5/2rarr²F_7/2 transition. The emission cross sections are calculated using two different methods and compared. The laser parameters of these Yb³⁺ -doped glasses are better than many reported glasses and crystals making them potential to fabricate high power laser and broadband optical amplifier in the wavelength region around ~1 mum     

A 200-$mu$V/e$^{-}$ CMOS Image Sensor With 100-ke$^{-}$ Full Well Capacity

A high-sensitivity CMOS image sensor keeping a high full-well capacity has been developed by introducing a new pixel having a small floating diffusion (FD) capacitance connected to a lateral overflow integration capacitor (LOFIC) through a MOS switch. The conceptual advantage of the small FD approach over conventional column amplifier approaches is compared and demonstrated. To ensure both the high sensitivity and the high full-well capacity, the low-light and the bright-light signals (S1 and S2) are output and reproduced without a visible SNR degradation at the S1/S2 switching point. As the most critical problem, the increase of the conversion gain variation in this approach is suppressed by applying a self-aligned offset structure to the small FD. A 1/4-in VGA format CMOS image sensor fabricated through 0.18-mum 2P3M process achieves 2.2-e^- rms noise floor with 200-muV/e^- conversion gain and 100-ke^- full-well capacity.     

360$^{circ}$ Star Coupler for Detecting Subwavelength Features

We propose a novel 360$^{circ}$ star coupler. We show theoretically how this coupler can detect perfectly conducting cylinders with radii significantly smaller than a wavelength, in the far field. We experimentally demonstrate detection of a metal probe using the 360 $^{circ}$ star coupler in a silica planar lightwave circuit. With improvements, this coupler may be able to perform subwavelength 2-D imaging.      

Design Considerations for Cascade $Delta Sigma $ ADC's

This brief discusses the design tradeoffs for cascaded delta-sigma (DeltaSigma) analog-to-digital converters. Increasing the order of the first loop allows a tradeoff between aggressive noise shaping and moderate operational transconductance amplifier (OTA) specifications. A comparison between fourth-order topologies indicates that for a cascade 3-1 topology, 55-dB OTA gain is sufficient for 96-dB signal-to-noise-distortion ratio while 5% coefficient mismatch results in less than 4-dB degradation. Dependent on the ratio between the power consumption of the digital recombination and decimation filter and that of the analog loop filter, the optimal topology can be chosen. A cascade 3-1 converter is most efficient when this ratio lies between 0.54 and 0.97. A design in a 65-nm CMOS technology demonstrates the performance of a cascade 3-1 converter.     

Eigendecomposition of Images Correlated on $S^{1}$, $S^{2}$, and $SO(3)$ Using Spectral Theory

Eigendecomposition represents one computationally efficient approach for dealing with object detection and pose estimation, as well as other vision-based problems, and has been applied to sets of correlated images for this purpose. The major drawback in using eigendecomposition is the off line computational expense incurred by computing the desired subspace. This off line expense increases drastically as the number of correlated images becomes large (which is the case when doing fully general 3-D pose estimation). Previous work has shown that for data correlated on S ¹ , Fourier analysis can help reduce the computational burden of this off line expense. This paper presents a method for extending this technique to data correlated on S ² as well as SO(3) by sampling the sphere appropriately. An algorithm is then developed for reducing the off line computational burden associated with computing the eigenspace by exploiting the spectral information of this spherical data set using spherical harmonics and Wigner-D functions. Experimental results are presented to compare the proposed algorithm to the true eigendecomposition, as well as assess the computational savings.     

Radix-3$,times,$3 Algorithm for The 2-D Discrete Hartley Transform

In this correspondence, we propose a vector-radix algorithm for the fast computation of a 2-D discrete Hartley transform (DHT). For data sequences whose length is a power of three, a radix-3 times 3 decimation in frequency algorithm is developed. It decomposes a length-N times N DHT into nine length-(N/3) times N (N/3) DHTs. Comparison of the computational complexity with known algorithms shows that the proposed algorithm, in some cases, reduces significantly the number of arithmetic operations.     

Spectroscopy and Diode-Pumped Laser Experiments of LiLuF$_{bf 4}$:Tm$^{{bf 3}+}$ Crystals

In this work we report on the 2-${mbi mu}$m laser emission of LiLuF ${_{bf 4}}$ crystals doped with Thulium trivalent ions (Tm:LLF) at different doping density up to 16%. We will present our results regarding growth, absorption and emission spectroscopy, Judd–Ofelt analysis and room temperature diode pumping laser experiments as a function of the dopant density. The best result is 56% of slope efficiency, with a maximum output power of 280 mW. The emission wavelength ranges between 1985 and 2038 nm, exploiting the vibronic emission of Tm in LLF.      

Reducing the Number of Comparators in Multibt $Delta Sigma $ Modulators

Multibit feedback, being one way of lowering DeltaSigma modulators power consumption, has a major obstacle: the number of components in the internal analog-to-digital converter (ADC) and digital-to-analog converter (DAC). Nevertheless, the number of comparators in the ADC can be significantly reduced depending on the order of noise-shaping and the oversampling ratio. In this paper, we propose an auto-ranging algorithm with a mechanism to keep the structure stable that emulates more quantization levels than that allowed by the number of comparators. As the recourse to segmented DACs allows lowering the complexity of the mismatch shaping encoder, the auto-ranging ADC brings the benefits of multibit feedback without the usual increase in size and power consumption. The internal number of bits in DeltaSigma modulators is no more restricted by the difficulty of building the flash ADC with a low voltage supply.     

Decay Dynamics of Excited Nd $^{+3}$ Ions in Nd:YVO $_{4}$ Following Weak Excitation

Decay dynamics of the upper-laser energy level of $hbox{Nd:YVO}_{4}$ are re-evaluated. In order to reduce the effects of re-absorption, comparative measurements among crushed samples with different doping concentrations were conducted. The magnitude of re-absorption was estimated experimentally by comparing the relative intensity of the emitted fluorescence spectra at different wavelengths, and estimated theoretically by employing a simplified model. The temporal decay dynamics are found to be non-exponential and the associated rate parameters are presented. The room temperature intrinsic life time value of the $^{4}hbox{F}_{3/2}$ energy level is found to be significantly shorter than the value accepted today.      

Stochastic Modeling of the Transform-Domain $varepsilon {rm LMS}$ Algorithm

This paper presents a statistical analysis of the transform-domain least-mean-square (TDLMS) algorithm, resulting in a more accurate model than those discussed in the current open literature. The motivation to analyze such an algorithm comes from the fact that the TDLMS presents a higher convergence speed for correlated input signals, as compared with other adaptive algorithms possessing a similar computational complexity. Such a fact makes it a highly competitive alternative to some applications. Approximate analytical models for the first and second moments of the filter weight vector are obtained. The TDLMS algorithm has an orthonormal transformation stage, accomplishing a decomposition of the input signal into distinct frequency bands, in which the interband samples are practically uncorrelated. On the other hand, the intraband samples are correlated; the larger the number of bands, the higher their correlation. The model is then derived taking into account such a correlation, requiring that a high-order hyperelliptic integral be computed. In addition to the proposed model, an approximate procedure for computing high-order hyperelliptic integrals is presented. A regularization parameter is also considered in the model expressions, permitting to assess its impact on the adaptive algorithm behavior. An upper bound for the step-size control parameter is also obtained. Through simulation results, the accuracy of the proposed model is assessed.     

Characterization of $m$-Sequences of Lengths $2^{2k}-1$ and $2^{k}-1$ With Three-Valued Cross Correlation

Considered is the distribution of the cross correlation between in-sequences of length 2^2k -1, where m = 2k, and m-sequences of shorter length 2^k -1. New pairs of m -sequences with three-valued cross correlation are found and the complete correlation distribution is determined. Finally, we conjecture that there are no more cases with a three-valued cross correlation apart from the ones proven here.     

Underdetermined Anechoic Blind Source Separation via $ell^{q}$-Basis-Pursuit With $q≪1$

In this paper, we address the problem of underdetermined blind source separation (BSS) of anechoic speech mixtures. We propose a demixing algorithm that exploits the sparsity of certain time-frequency expansions of speech signals. Our algorithm merges lscr^q -basis-pursuit with ideas based on the degenerate unmixing estimation technique (DUET) [Yiotalmaz and Rickard, "Blind Source Separation of Speech Mixtures via Time-Frequency Masking," IEEE Transactions on Signal Processing, vol. 52, no. 7, pp. 1830-1847, July 2004]. There are two main novel components to our approach: 1, our algorithm makes use of all available mixtures in the anechoic scenario where both attenuations and arrival delays between sensors are considered, without imposing any structure on the microphone positions, and 2, we illustrate experimentally that the separation performance is improved when one uses lscr^q-basis-pursuit with q < 1 compared to the q = 1 case. Moreover, we provide a probabilistic interpretation of the proposed algorithm that explains why a choice of 0.1 les q les 0.4 is appropriate in the case of speech. Experimental results on both simulated and real data demonstrate significant gains in separation performance when compared to other state-of-the-art BSS algorithms reported in the literature.     

A 3$,times,$5-Gb/s Multilane Low-Power 0.18-$mu{hbox {m}}$ CMOS Pseudorandom Bit Sequence Generator

A low-power, three-lane, pseudorandom bit sequence (PRBS) generator has been fabricated in a 0.18-mum CMOS process to test a multilane multi-Gb/s transmitter that cancels far-end crosstalk. Although the proposed PRBS generator was designed to produce three uncorrelated 12-Gb/s PRBS sequences, measurement results included in this paper have been obtained at only 5 Gb/s due to test setup limitations. The prototype employs a CMOS latch optimized to operate at frequencies close to the of the process and a current-mode logic (CML) MUX with modified active inductor loads for better high-speed large-signal behavior. In order to reduce the power consumption, a quarter-clock rate linear feedback shift register (LFSR) core in a power-efficient parallel architecture has been implemented to minimize the use of power-hungry, high-speed circuitry. Further power reduction has been achieved through the clever partitioning of the system into static logic and CML. In addition, the prototype design produces three uncorrelated 12-Gb/s data streams from a single quarter-rate LFSR core, thereby amortizing the power across multiple channels which lowers the power per channel by 3 times. The total measured power consumption at 5 Gb/s is 131 mW per lane and the calculated figure of merit per lane is 0.84 pJ/bit, which is significantly better than previously published designs.     

A Quantization Noise Pushing Technique for $DeltaSigma$ Fractional- $N$ Frequency Synthesizers

This paper demonstrates our proposed quantization noise pushing technique, which moves the quantization noise to higher frequencies and utilizes the low-pass characteristic of the phased-lock loop (PLL) to further suppress the quantization noise. In addition, it can separate the operating frequency of the DeltaSigma modulator and the comparison frequency of the phase/frequency detector (PFD) so as to reduce the loop gain of the PLL and lower the in-band phase noise. This synthesizer was fabricated using the UMC 0.18-mum CMOS process. The chip area measures 0.85 mm². The supply voltage is 2 V, corresponding to a total power consumption of 26.8 mW. The experimental results show that, with this technique, the in-band phase noise can be lowered by 12 dB, while the out-of-band phase noise can be reduced by more than 15 dB, compared to a synthesizer with the same PFD comparison frequency.