Naoyuki Aikawa

A design of the stopband variable FIR digital filters using spectral parameter

Several applications in digital signal processing demand variable digital filters with arbitrary variable frequency response. However, the design method of filters having variable piecewise large attenuation characteristics in the stopband is not proposed. This paper describes the design method of variable FIR digital filters having changed piecewise large attenuation characteristics in the stopband. The basic idea is to represent the coefficients of variable transfer function as the polynomials using spectral parameter. We design each filter with difference stopband attenuation by successive projections method. Then we approximate the obtained filter coefficient by the polynomials using spectral parameter in the least-square sense.

Designing FIR Digital Filters with the Specified Maximum Group Delay Errors

This paper describes a design method of FIR digital filters that meet simultaneously amplitude and group delay specifications using successive projection method. The proposed method allows the direct approximation of the group delay characteristics, and it can also restrict the group delay characteristics within the preselected allowable errors. It is shown by numerical examples that the proposed method provides very good results compared with the previous methods.

A closed form transfer function of low delay bandpass FIR filters with maximally flat characteristics in the passband and the transmission zeros in the stopband

The large group delay of the high order FIR fillers is unacceptable in some applications. So, recently, how to reduce the group delay of FIR filters has been studied intensively. To reduce the ringing in the time domain and to maximize the stopband attenuation, it is useful to design FIR filters with maximally flat characteristics in the passband and transmission zeros in the stop band. We present a mathematically closed form transfer function of low delay bandpass FIR filters with maximally fiat amplitude in the passband and the transmission zeros in the stopband. Therefore, the designing filters are very simple.

Kernel with block structure for sampling rate converter

Sampling rate conversion using the filter banks is proposed in the field of digital signal processing. However, in sampling rate conversion with a rational factor, the computational complexity may become very large. Moreover whenever the sampling rate is changed, it is necessary to design the filter again. In this paper, hence, we present a kernel with block structure for sampling rate conversion. As the filter proposed has the impulse response approximated by polynomials, it is unnecessary to redesign whenever the sampling rate is changed. The kernel proposed has the block structure that the impulse response of the sampling section since the third is represented by the polynomial used for the second sampling section. Therefore, the filter has less memory. Moreover, the filter has the advantage that it is possible to correspond to arbitrary fractional sampling rate conversion.

A design method of low delay lowpass FIR filters with maximally flat characteristics in the passband and the transmission zeros in the stopband

The large group delay of high order FIR filters is unacceptable in some applications. So, recently, methods to reduce the group delay of FIR filters have been studied intensively. To reduce the ringing in the time domain and to maximize the stopband attenuation, it is useful to design FIR filters with maximally flat characteristics in the passband and transmission zeros in the stop band. We present a mathematically closed form transfer function of low delay lowpass FIR filters with maximally flat amplitude in the passband and the transmission zeros in the stopband. Therefore, the designed filters are very simple. Moreover, we present also a design method of low delay lowpass FIR filters with maximally flat amplitude in the passband and equiripple in the stopband by using an iterative method of a closed form transfer function and the Remez algorithm.

Minimax approximation of minimum phase FIR filters

This paper presents a directly design method of FIR filters with minimum phase characteristics using successive projections (SP) method. We use Rouches theorem for coefficients update algorithm in SP method to restrict the roots of transfer function inside the unit circle and on the unit circle. The proposed method is an iterative optimization technique and its algorithm is as simple as the conventional SP method. The usefulness of the proposed method is verified through the examples.