Koichi Ichige

Accurate estimation of minimum filter length for optimum FIR digital filters

This paper presents an accurate estimation formula of minimum filter length for optimum (minimax criterion based) linear-phase finite impulse response (FIR) low-pass digital filters. Two estimation formulae have been already proposed; however, they have some problems which lead to wrong estimation. Discussing the problems based on our experimental results, a new estimation formula is newly proposed. The accuracy of the proposed formula is evaluated in comparison with that of the conventional formulae. Furthermore, the proposed formula is applied to the design of high-pass, band-pass, and band-stop filters. The estimation accuracy is discussed also in this case.

Design of Jacobi EVD processor based on CORDIC for DOA estimation with MUSIC algorithm

Computing the eigenvalue decomposition (EVD) of a symmetric matrix is a frequently encountered problem in adaptive (or smart or software) antenna signal processing, for example, super resolution DOA (direction of arrival) estimation algorithms such as MUSIC (multiple signal classification) and ESPRIT (estimation of signal parameters via rotational invariance technique). In this paper the hardware architecture of the fast EVD processor of a symmetric correlation matrix for the application of an adaptive antenna technology such as DOA estimation is proposed and the basic idea is also presented.

An Explicit High-Resolution DOA Estimation Formula for Two Wave Sources

This paper presents a novel and simple high-resolution DOA (direction-of-arrival) estimation algorithm which corresponds to the case of two incident waves received by ULA (uniform linear array). The proposed DOA estimation formula does not employ eigendecomposition, iteration, optimization or space averaging, therefore it requires very low computational cost but achieves high resolution. Surprisingly, the present simple DOA estimator has almost the same accuracy with (and sometimes better than) major conventional DOA estimation algorithms. The estimation accuracy and the computational cost are evaluated through computer simulation in comparison with those by some major conventional algorithms

An approximation for discrete B-splines in time domain

A simple discrete version of B-splines defined as a multifold discrete convolution of sampled rectangles is proposed in the analogy of B-splines being multifold convolution integrals of rectangular functions. Then it is proven that its staircase interpolation tends to the B-spline when the sampling interval goes to zero. This version can be regarded as an approximation for the discrete B-splines established in the literature, and it is faster in numerical evaluation.

Real-time smart antenna system incorporating FPGA-based fast DOA estimator

This paper describes a practical hardware implementation of uplink smart antenna system useful for macrocellular base stations. This system incorporates a fast DOA (direction of arrival) estimator which is called UMP (unitary MUSIC processor) using the dedicated circuit device of FPGA (field programmable gate array). This system steers the mainlobe for the user basically with the Dolph-Chebyshev beam. In order to avoid undesirable interference reception by broad mainlobe, an optional null-steering processing cancels the interferers within the mainlobe coverage with notch beams which are pre-computed and stored in ROM (read only memory). The beamforming weight is computed by a simple convolution operation of the precomputed Dolph-Chebyshev beam and optional canceling beam, thus the computation load for weight generation is extremely small. This paper presents the estimation performance of the UMP through the hardware level fixed point simulation and measurements. And total performance evaluation of this system under AWGN and multipath fading channel with small angle spread is discussed.

Intra Prediction Mode Decision in H.264/AVC Using DCT Coefficients

This paper presents a high-speed procedure of intra prediction mode decision in H.264/AVC using DCT coefficients. Intra prediction mode is one of the techniques that are newly introduced in H.264/AVC. This technique can enhance compression efficiency in an intra frame, however a large computational cost is often needed for the prediction. Recalling that DCT bases are well-related to intra prediction modes, we develop a novel approach of intra prediction mode decision using DCT coefficients. The proposed technique is evaluated in comparison of some conventional techniques through computer simulation

Jitter effect on digital downconversion receiver with undersampling scheme

Undersampling phase modulated signals directly at high frequency band, the effect by ADCs aperture jitter characteristics and sampling clock instability of the system can not be ignored. The sampling jitter brings additional phase noise to the constellation pattern, thus the BER (bit error rate) performance will be degraded. This paper presents the relationship between the input frequency to ADC (analog-to-digital converter) and the sampling jitter in the digital IF (intermediate frequency) downconversion receiver with undersampling scheme. The computer simulation results with theoretical IF sampling receiver model and the measurement result with a real hardware will be presented. According to the results, for wireless LAN standard the effective IF QPSK signal input frequency of ADC was limited below around 300 MHz with RMS (root mean square) jitter of 25 ps for 40 MHz sampling rate.

Quadratic spline interpolator

A simple system is proposed which generates a quadratic spline function interpolating a given discrete-time signal. It works as a D-A converter which is free from phase distortions and whose output is smooth. The output is constructed as two-fold integration of a staircase signal. A kind of sampled data feedback is employed to stabilize the system. Its circuit is mainly composed of a pair of D-A and A-D converter chips and two analogue integrators. This hardware complexity is about a quarter of current systems.

Implementation of FPGA based fast DOA estimator using unitary MUSIC algorithm [cellular wireless base station applications]

This paper proposes the practical implementation of a DOA estimation system, using an FPGA (field programmable gate array), that is a key technique in the realization of the DOA-based adaptive array antenna for cellular wireless base-stations. It incorporates the spectral unitary MUSIC (multiple signal classification) algorithm, which is one of the representative super resolution DOA estimation techniques. This paper describes the DSP design and real hardware implementation of the unitary MUSIC algorithm. This system achieves a high performance in the eigenvalue decomposition (EVD) and MUSIC angular spectra computation with a cyclic Jacobi processor based on CORDIC (coordinate rotation digital computer) and spatial DFT (discrete Fourier transform), respectively. All DSP functions are computed by only fixed-point operation with finite bit-length to meet the requirements of fast processing and low power consumption due to the simplified and optimized architecture.

Direction-of-arrival estimation of coherent sources for ULA based on the relation between array covariance matrix elements

This paper presents a Direction-Of-Arrival (DOA) estimation method of coherent sources for Uniform Linear Array (ULA) based on the relation between array covariance matrix elements. First we analyze the covariance matrix in array signal processing and formulate the relations between the matrix elements. Then we develop a novel DOA estimation method of coherent sources for ULA based on the analyzed relations. Performance of the proposed method is evaluated through computer simulation.