R. S. Tomar

Fully integrated electronically tunable universal biquad filter operating in current-mode

A new current-mode universal filter structure consisting of three current-follower transconductance amplifiers (CFTAs) and two grounded capacitors is described in this paper. By the proper selection of three current input (s), it can realize all the five standard filtering responses namely, low pass (LP), band pass (BP), high pass (HP), band reject (BR), and all pass (AP) at single high impedance current output terminal. Thus, the proposed biquad structure is a multi-input single-output type filter configuration. It offers number of remarkable features such as wide range of orthogonal electronic tunability of filter parameters, capability to realize various filtering responses without using inverted current input signal(s) and low sensitivities with respect to active and passive components. The circuit performance is examined through P-SPICE simulation on ORCAD tools.

Current tunable current-mode TISO biquad filter consisting of two MCFTAs and minimum number of grounded capacitors

This paper introduces a new current tunable current-mode biquad filter topology which is based on the active elements namely, modified current follower transconductance amplifiers (MCFTAs) and two grounded capacitors. It can realize all the five standard filtering responses such as band pass (BP), low pass (LP), high pass (HP), band reject (BR), and all pass (AP) at single high impedance current output through appropriate selection of three applied current inputs. So this circuit is three input single output (TISO) current-mode filter topology. The circuit offers an advantage of wide range of orthogonal electronic tunability of pole-frequency and quality factor and capable of realizing various filtering responses without using inverted and double current input signal. Moreover, the circuit also provides low active and passive sensitivities. Performance of the circuit is verified through P-SPICE simulation on ORCAD tool.

ZC-CFTA-based trans-impedance-mode universal biquad filter with electronic tuning

In this topic, a new trans-impedance-mode filter structure realizing low pass (LP), band pass (BP), band reject (BR), high pass (HP) and all pass (AP) filtering functions using three Z-copy current follower trans-conductance amplifiers (ZC-CFTAs) and two grounded capacitors is proposed. The proposed structure realizes all the five standard filtering functions, but one at a time without requiring any inverting type current input signal(s) and component matching conditions. Since ZC-CFTAs are implemented using CMOS topology, thus filter circuit provides temperature insensitive performance parameters. Moreover, the proposed circuit enjoys the features of low active/passive sensitivities, independent electronic tunability of pole frequency and quality factor. The workability of the proposed trans-impedance-mode filter is verified using PSPICE circuit simulation software.

Single input four output voltage-mode biquad filter with electronic tuning

In this paper a new single current controlled current conveyor trans-conductance amplifier (CCCCTA) based electronically tunable voltage-mode biquad filter is proposed. The proposed voltage-mode filter employs only one resistor and three capacitors as passive elements. It can simultaneously realize low pass (LP), band pass (BP), band reject (BR) and high pass (HP) filtering functions using single voltage input signal. The circuit possesses low active and passive sensitivity. Moreover, both ω0 and Q can be electronically controlled by the bias currents of the CCCCTA. PSPICE simulation results are included for verification of proposed circuit.

A novel hybrid DWPT and MDCT based coding technique for sounds of musical instruments

In this paper, a new hybrid multi-stage musical instrument sound signal compression method, based on DWPT and MDCT using efficient psychoacoustic models is proposed. The primary objective is to perform lossy and perceptually transparent compression on the sounds of various Indian musical instruments. Firstly, the original sound signal is decomposed into wavelet packets using an optimal wavelet basis. Wavelet packets are then run through psychoacoustic model in wavelet domain to determine auditory masking level for thresholding, which in turn is used to perform thresholding of wavelet coefficients in respective sub-bands. Further, audio signal coefficients are partitioned into frames which overlap in such a way that each block gets 512 samples and windowed using a hanning window with 1/16 frame overlap. Secondly, MDCT is applied to each block to de-correlate the spectral information. Removal of spectral redundancy is achieved by compressing the subordinate components more than the dominant components. The resulting signal is quantized with variable number of bits, which are determined based on the results of the psychoacoustic model in FFT domain. This technique provides an efficient way to exploit key strengths of both DWPT and MDCT.