Design and FPGA Implementation of Reconfigurable Linear-Phase Digital Filter With Wide Cutoff Frequency Range and Narrow Transition Bandwidth

Abstract

Reconfigurable filters based on the spectral parameter approximation (SPA) technique and its combination with other techniques provide a continuous control over the cutoff frequency $(f_c)$ . However, when very wide $f_c$ range and narrow transition bandwidth is desired, these filters either fail to satisfy some of the specifications or have extremely high complexity. In this brief, we propose an interpolated SPA (ISPA) filter that overcomes all the limitations of all the existing SPA technique based filters, and achieves very wide $f_c$ range (equal to approximately the entire Nyquist band) and narrow transition bandwidth along with small passband ripple and high stopband attenuation. Comparison with the state-of-the-art reconfigurable filters is provided via a design example, which shows that the ISPA filter achieves more than 50% savings in the number of multipliers compared to the filter based on the combination of SPA and modified coefficient decimation techniques. The field-programmable gate array implementation results show that the ISPA filter has much lesser group delay and much higher operating speed, but incurs moderate penalty in terms of area compared to the filter based on the combination of frequency transformation and interpolation techniques.