A quadratic spline function generator

A function generator is developed which purges digital-to-analog (D-A) conversion of phase distortions by replacing both the hold circuit and the analog low-pass filter. This generator implements interpolation of a discrete-time signal by a quadratic spline function which is a smooth piecewise polynomial. Fidelity in the amplitude characteristic of the generator is estimated. It is also proved that the generator is of linear phase. The generator is constructed in the form of a FIR (finite impulse response) digital filter with a time-varying impulse response. Based on the linear phase characteristic, the generator is useful in D-A conversion, especially in audio signal processing applications.<>