Linear-Phase VDF Design With Unabridged Bandwidth Control Over the Nyquist Band

Abstract

This brief presents a low-complexity linear-phase variable digital filter (VDF) design with tunable lowpass (LP), highpass (HP), bandpass (BP), and bandstop (BS) responses anywhere over the entire Nyquist band. The spectral-parameterapproximation-based VDFs (SPA-VDFs) was designed using the Farrow structure and has advantages of linear phase, lower group delay, and fewer variable multipliers. However, the total gate count and the dynamic range of filter coefficient values of SPA-VDFs significantly increase with the tunable range of cutoff frequency, which limits their usefulness in emerging signal processing and wireless communication applications. In addition, existing VDFs need to update either filter coefficients or need parallel filter structures to obtain variable LP, HP, BP and BS responses. In this brief, a new VDF design is proposed by deftly integrating SPA-VDF with the modified coefficient decimation method (MCDM), and it will be referred to as SPA-MCDM-VDF. The SPA-MCDM-VDF provides LP, HP, BP, and BS responses with unabridged center frequency and bandwidth control over the entire Nyquist band without the need for hardware reimplementation or coefficient update. The complexity comparisons show that the SPA-MCD-M-VDF offers substantial savings in gate count, group delay, and number of variable multiplications over other linear-phase VDFs. Index Terms-Modified coefficient decimation method (MCDM), spectral parameter approximation (SPA), variable digital filter (VDF).

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

“…One of the techniques of reconfigurable digital filter design, the spectral parameter approximation (SPA) technique [3][4][5][6][7][8][9][10], provides absolute control over fc. The SPA technique has also been combined with other techniques to design reconfigurable filters [11,12]. However, as the desired fc range becomes wider and/or the desired transition bandwidth (tbw) becomes narrower, the complexity of SPA based filters increases rapidly along with the values of the sub-filter coefficients, making the fixed-point implementation difficult.…”

“…However, as the desired fc range becomes wider and/or the desired transition bandwidth (tbw) becomes narrower, the complexity of SPA based filters increases rapidly along with the values of the sub-filter coefficients, making the fixed-point implementation difficult. When very wide fc range is desired along with very narrow tbw and high stopband attenuation, the SPA technique based methods [3][4][5][6][7][8][9][10][11][12] either fail to satisfy the specifications or have extremely high complexity.…”

“…The ISPA filter proposed in this brief overcomes all the limitations of the SPA filters [3][4][5][6][7][8][9][10], and other reconfigurable filters based on SPA technique [11,12]. The fc of the ISPA filter is variable over approximately the entire Nyquist band and it provides narrow tbw along with small passband ripple and high stopband The rest of the paper is organized as follows.…”

Decision making policy for RF energy harvesting enabled cognitive radios in decentralized wireless networks

“…Hence, a 6 hardware reconfiguration penalty is mainly contributed by the digital front-190 end (and hence, variable digital filters) since the analog front-end is fixed. Reader can refer to [22][23][24][25][26] for more details about variable digital filters. Among them [22][23][24][25][26], variable digital filters in [23,24] offer lowest subband switching penalty due to fewer number of variable multipliers.…”

“…Among them [22][23][24][25][26], variable digital filters in [23,24] offer lowest subband switching penalty due to fewer number of variable multipliers. The implementation complexity of the VDF in [24] is lower than [23]. 2.…”