Cheong-Fat Chan

An efficient MFCC extraction method in speech recognition

This paper introduces a new algorithm of extracting MFCC for speech recognition. The new algorithm reduces the computation power by 53% compared to the conventional algorithm. Simulation results indicate the new algorithm has a recognition accuracy of 92.93%. There is only a 1.5% reduction in recognition accuracy compared to the conventional MFCC extraction algorithm, which has an accuracy of 94.43%. However, the number of logic gates required to implement the new algorithm is about half of the MFCC algorithm, which makes the new algorithm very efficient for hardware implementation

Reversed nested Miller compensation with voltage buffer and nulling resistor

This paper presents a new reversed nested Miller compensation technique for multistage operational amplifier (opamp) design. The new compensation technique inverts the sign of the right half complex plane zero and shifts the frequency of the complex conjugate poles to a higher frequency. Simulation results indicate that the gain-bandwidth product and settling time are improved by factors of two and three, respectively, without degrading stability and power consumption. To verify the proposed technique, a three-stage opamp is fabricated with 0.6-/spl mu/m CMOS technology. The measured results of the test circuit agree with the results that are obtained from theoretical analysis and circuit simulation.

A wideband compact parallel-strip 180/spl deg/ Wilkinson power divider for push-pull circuitries

A Wilkinson power divider with a differential output implemented in parallel-strip-line (PSL) is proposed. Taking full advantages of the PSL technology and a three-stage cascaded design, more than 170% impedance and isolation bandwidths are obtained. Inherent to the PSL structure, the 180deg differential output is frequency-independent. A class-B push-pull power amplifier employing the devised concept is designed, showing a peak efficiency of 44% over a 4-GHz bandwidth. Without exploiting any extra and external low-pass filters, the proposed design can produce startling second-harmonic suppressions (more than 50dB) over the whole working dynamics and operated bandwidth

A UWB Bandpass Filter With Two Transmission Zeros Using a Single Stub With CMRC

A compact bandpass filter is proposed for lower-band ultra-wideband applications. It entails the design concept of a stub-tapped half-wavelength line resonator which provides three transmission poles in the passband and two transmission zeros at the high and low rejection bands. The two stubs are replaced by a single dual-band stub and the parallel coupled-line structures are meandered, leading to a compact size of 0.26lambdag by 0.32lambda g

Application of diagonally perturbed incomplete factorization preconditioned conjugate gradient algorithms for edge finite-element analysis of Helmholtz equations

The diagonally perturbed incomplete factorization preconditioning scheme is applied to the conjugate gradient (CG) method for solving a large system of linear equations resulting from the use of edge-based finite-element method (FEM). This scheme contains more global information about the coefficient matrix when compared with banded-matrix schemes. The efficient implementation of this preconditioned CG (PCG) algorithm is described in detail for complex coefficient matrix equation. On several electromagnetic problems the PCG approach converges in CPU time, which is 8.6-19.5 times shorter with respect to the CG approach. By comparison with other preconditioned techniques, the results demonstrate that incomplete factorization preconditioning strategy is especially effective for CG iterative method when edge-FEM is applied to solve large-scale time-harmonic electromagnetic field problems

A Trapeizform U-Slot Folded Patch Feed Antenna Design Optimized With Jumping Genes Evolutionary Algorithm

A novel design of trapeizform U-slot folded patch feed antenna is presented in this paper. It is optimized by an evolutionary based optimization scheme which is capable of producing an antenna design that has a wide impedance bandwidth but small in dimension size. The optimized design was also experimentally verified by its hardware prototype in which 101.3% measured impedance bandwidth was obtained compared with its simulated bandwidth of 104%. Also, both the effectiveness of the optimization methodology and the proposed antenna configuration have been justified through comparison results.

A feedback control circuit design technique to suppress power noise in high speed output driver

In todays sub-micron CMOS integrated circuit technology, high speed output switching signals interacting with external inductance and capacitance produce noise which contaminates output signals and power buses. A Feedback Control Slew Rate Output Driver (FCSROD) which reduces the noise spike down to approximately 64% of a conventional output buffer without incurring the penalty of the propagation delay and even the rise/fall time is described. This effective power noise suppression is achieved by using distributed and weighted switching driver segments in conjunction with feedback control to control the output drivers slew rate. Dynamic short circuit current which is generated while both pFET and nFET are conducting is also minimized to reduce di/dt noise. FCSROD was compared with a conventional and the controlled slew rate output buffer, showing 64% noise reduction comparing to the conventional driver, and 22% improvement in both propagation delay and rise/fall time comparing with the controlled slew rate output driver.

An HMM-based speech recognition IC

This paper presents the design, simulation and measurement results of a Hidden Markov Model (HMM) based isolated word recognizer IC with double mixtures. Table look-up technique is employed in this design. The chip operates at 20 MHz at 3.3 V. The recognition time is 0.5 s for a 50-word speech library. The speech IC has been verified with 467 test speech data and the recognition accuracy is 93.8%. A reference software recognizer using the same algorithm and speech library has a recognition accuracy of 94.2%. The new speech IC that uses a table look up to reduce the complexity of the circuit has approximately the same recognition accuracy as an ideal software recognizer.

A Fully Differential Band-Selective Low-Noise Amplifier for MB-OFDM UWB Receivers

A band-selective low-noise amplifier (BS-LNA) for multiband orthogonal frequency-division multiplexing ultra-wide-band (UWB) receivers is presented. A switched capacitive network that controls the resonant frequency of the LC load for the band selection is used. It greatly enhances the gain and noise performance of the LNA in each frequency band without increasing power consumption. Moreover, a fully differential configuration is employed to suppress the common-mode switching noise that is generated during the band transition interval. Fabricated in a 0.18-mum CMOS process, the BS-LNA achieves a peak power gain of 16 dB, a minimum noise figure of 2.74 dB, and an third-order input intercept point of -8.8 dBm at a current consumption of 7.95 mA from a 1.5-V supply. Little performance degradation is observed when the current consumption is reduced by half. The experimental results also show a worst-case band-switching time of less than 3.4 ns, with a peak switching noise voltage of less than 70 muV at the output.

Fast analysis of electromagnetic scattering of 3-D dielectric bodies with augmented GMRES-FFT method

The problem of electromagnetic scattering by three-dimensional dielectric bodies is formulated in terms of a weak formulation of the domain-integral equation. Applying Galerkins method with rooftop functions as basis and testing functions, the integral equation can be solved by the Krylov-subspace iterative fast Fourier transform (FFT) methods. However, poor convergence is observed when the relative permittivity of the scatterer becomes large. In order to relieve this trouble, an augmented generalized minimum residual method (AGMRES) is presented. Comparisons between several typical iterative methods are made to show the efficiency of our proposed method.