Shotaro Nishimura

A new class of very low sensitivity and low roundoff noise recursive digital filter structures

A class of new structures is proposed, for the realization of the recursive digital filter with poles near the unit circle, by introducing the particular type of delay replacement scheme in the existing digital filter structure and then, inserting, delays at the. proper places to avoid the delay-free loops. By applying the proposed method to the second-order direct form structures, new structures are found with very low magnitude transfer function sensitivities with respect to multiplier coefficients and low roundoff noises. Some numerical results are also presented.

Design of digital bandpass/bandstop filters with independent tuning characteristics

Two different approaches are proposed in this paper for the design of bandpass/bandstop filters with independent tunning of the center (notch) angular frequency ω 0 and the 3-dB attenuation (notch) bandwith Ω c . These approaches lead to a variety of two-multiplier structures for the realization of second-order bandpass/bandstop digital filters in which one multiplier controls ω 0 and the other multiplier adjusts Ω c

A lattice-based adaptive IIR notch filter and its application to FSK demodulation

In this paper, an application of a simplified second-order lattice-based adaptive IIR notch filter to binary FSK demodulation is presented. The design method and performance evaluation of the demodulator, based on mean-squared error analysis of the steady-state variable coefficient fluctuations of the adaptive notch filter are studied. Derived analytical results are compared with computer simulation results for confirmation.

Gradient-based complex adaptive IIR notch filters for frequency estimation

In this paper, we present a new structure for a complex adaptive IIR notch filter which is useful for the detection of complex sinusoids in communication and radar systems. The proposed structure is based on the direct form first-order complex notch filter using a gradient-based algorithm. A quantitative analysis for convergence properties is developed. It has been shown that the convergence speed does not depend on the variance of input white noise. The effects of colored Gaussian noise on convergence speed have been analyzed. By using the proposed first-order section, a new cascaded structure for the complex adaptive notch filter is also shown. The results of computer simulation are shown which confirm the theoretical prediction.

Complex adaptive notch filter for detection of real sinusoid

This paper presents a new realization of adaptive notch filter based on a cascade of complex first-order notch filters. Unbiased frequency estimation of a real sinusoid has been achieved by thinning the notch bandwidth. It has been shown that the simple closed form of mean square error (MSE) for frequency estimation is given by using the results for first-order complex notch filter and its robustness to the frequency of input sinusoid has been shown. Computer simulation results are presented to validate the analysis.

Convergence analysis of complex adaptive IIR notch filters

In this paper, we present a new structure for the complex adaptive IIR notch filter which is useful for the detection of complex sinusoids in communication and radar systems. The proposed structure is based on the direct form first-order complex notch filter using a gradient-based algorithm. A quantitative analysis of convergence properties is developed. It has been shown that the convergence speed does not depend on the variance of input white noise. The effects of colored Gaussian noise on convergence speed have been analyzed. By using the proposed first-order section, a new cascaded structure for the complex adaptive notch filter is also shown. The results of computer simulation are shown which confirm the theoretical prediction.

Gradient-based algorithms for a complex coefficient adaptive IIR notch filter: steady-state analysis and application

In this paper, a method for steady-state analysis of gradient-based algorithms for a complex coefficient adaptive infinite impulse response (IIR) notch filter is presented. Accurate expressions of estimation mean square error (MSE) for variable coefficients are derived by approximating the power spectral densities (PSD) of estimation errors. Suppression of a complex sinusoidal interference in a direct-sequence quadrature phase shift keying (DS QPSK) system using the algorithms is also presented. Computer simulations are presented to support the validity of the analysis.

Design of Two-Dimensional Adaptive Digital Notch Filters

In this paper, a method for realizing a two-dimensional (2-D) adaptive notch filter is proposed. The obtained 2-D structure contains a pair of one-dimensional (1-D) second-order IIR notch filters and a pair of 1-D first-order allpass filters. The method has been successfully applied for the removal of a sinusoidal interference superimposed on an image.

Tracking properties of complex adaptive notch filter for detection of multiple real sinusoids

This paper presents a new realization of adaptive notch filter based on a cascade of adaptive IIR notch filters using complex coefficient first-order notch filters. The input is multiple real linear chirp signals embedded in a white Gaussian noise. Closed-form expression for frequency tracking mean square error (MSE) is given. Optimum step size parameter and notch bandwidth coefficient that minimize the tracking MSE are also derived. Computer simulation results are presented to validate the analysis.

Rejection of narrow-band interference in BPSK demodulation using adaptive IIR notch filter

In this paper, an application of a second-order IIR adaptive notch filter for the rejection of narrow-band interference in BPSK demodulation is presented. The effects of the filter on the decoded binary output is studied by comparing the probability of binary error before and after interference cancellation.