Group Delay of Fractional n+α-Order Bessel Filters

In this paper we present the realization of fractional-order analog filter with Bessel approximation, having linear phase response, which is also usually represented by a constant group delay. There are many applications such as analogue video signal processing, radar and sonar receivers, hard disk drive read channel applications, analog front end of biomedical signal processing, where linear phase response is desirable. Optimally designed Bessel filter can provide better transient response in the passband, it reduces overshoot, ringing and provides minimal phase distortion. In this work we research Bessel approximation with the non-integer order $\mathrm{n}+\alpha;\mathrm{n}$ is integer number and $0\lt\alpha\lt1$. The influence of non-integer filter order to the value of the constant group delay of the filter is presented. It is shown that the group delay value can be additionally tuned by changing the parameter α.