Shail Bala Jain

On the design of multi notch filters

A methodology for designing FIR multi notch filters (NFs) derived from second-order prototype IIR NFs is suggested. Rejection bandwidth for the designed filter can be controlled by suitable choice of ‘r’, the pole radius of the IIR prototype NFs. The suggested multi NF can also be adapted to eliminate second-, third- and fourth-order harmonics of periodic noise besides the fundamental noise frequency component. A special case when two notch frequencies ω1 and ω2 are such that [(cosω1)(cosω2) = − 1/2] has also been discussed. The IIR multi NF design for this special case results in reduction of the number of multipliers without affecting the response of the desired NF. For the aforereferred condition, the required coefficients of impulse response of FIR multi notch filter get reduced to almost half in number resulting in reduced computations. The number of zero coefficients further reduces with increase in ‘r’ value. In addition, the frequency response becomes better, with reduced ripples in the pass bands, when ‘r’ is increased and length ‘L’ of the FIR NF is chosen appropriately. Copyright

Fast communication: Design of maximally flat linear phase FIR notch filter with controlled null width

A technique for designing a maximally flat, linear phase FIR notch filter with controlled null width is presented in this paper. Design analysis is carried out with first-, third- and fifth-order zero derivative constraints of the amplitude response of the FIR filter at notch frequency. An algorithm is presented for designing maximally flat, linear phase FIR notch filter with specified null width around specified notch frequency with third-order zero derivative constraint at the notch frequency. Detailed analysis in this paper shows that the null width of a maximally flat, linear phase FIR notch filter can be controlled by suitable selection of individual zero-odd-order derivatives and also by the successive addition of zero-odd-order derivatives at the notch frequency.

Optimum HMM combined with vector quantization for hindi speech word recognition

Abstract This paper proposes an optimum speaker-independent, isolated word Hidden Markov Model (HMM) recognizer for the Hindi language. The recognition system is based on the combination of the vector quantization (VQ) technique at the acoustical level and the Markovian modeling at the recognition level. The recognizer consists of three modules – feature extraction, vector quantizer and HMM training and testing modules. The scheme proposed here firstly computes the acoustic features in terms of the Linear Predictive Cepstral LPC coefficients, Mel-Frequency Cepstral coefficients and delta MFCC along with noise and silence detection. Then, codebooks are created using VQ, and finally in the recognition phase, an optimum set of parameters are derived from different phases for getting the highest recognition score. The training and testing database consists of a set of 35 utterances of nine Indian cities/states and 35 utterances of nine digits spoken in Hindi by male and female speakers. The recognition rate was observed to be 98.61%.

Unified Recursive Structure for Forward and Inverse Modified DCT/DST/DHT

Abstract This paper proposes implementation of the Modified Discrete Sine Transform (MDST) and Inverse MDST (IMDST) using recursive structures. The formulae required for recursive structures have been derived. Discrete Hartley Transform (DHT), a real-valued transform, is closely related to Discrete Fourier Transform (DFT) of a real-valued sequence and hence its use as an alternative to the Fourier Transform avoids complex arithmetic. This paper presents Modified Discrete Hartley Transform (MDHT)/Inverse MDHT (IMDHT) using Modified Discrete Cosine Transform (MDCT)/ Inverse MDCT (IMDCT) and MDST/Inverse MDST (IMDST) recursive structures. The proposed structures are used for simultaneous computation of MDCT/MDST/MDHT of length N (divisible by four) and their Inverse (IMDST/IMDHT). The proposed structures are parallel, simple, regular and therefore highly suitable for VLSI implementation.

Analytical modeling of drain current and RF performance for double-gate fully depleted nanoscale SOI MOSFETs

A new 2D analytical drain current model is presented for symmetric double-gate fully depleted nanoscale SOI MOSFETs. Investigation of device parameters like transconductance for double-gate fully depleted nanoscale SOI MOSFETs is also carried out. Finally this work is concluded by modeling the cut-off frequency, which is one of the main figures of merit for analog/RF performance for double-gate fully depleted nanoscale SOI MOSFETs. The results of the modeling are compared with those obtained by a 2D ATLAS device simulator to verify the accuracy of the proposed model.

Spectrum Saving through Fixed Mobile Convergence: Mobile Bandwidth Saving Estimate Model

Abstract The Indian domestic telecom sector has seen phenomenal growth over the past few years. The number of mobile phone subscribers in India has already crossed 500 million by December 2009 and increasing at about 15 million subscribers per month. This phenomenal growth also has lead to poor quality of service with frequent call drop outs, and so on, due to heavy traffic congestion, especially in urban areas. The problem is compounded further by the limited amount of spectrum available for mobile cellular networks. This leads to a situation where the mobile service provider has to significantly increase the number of cell sites for capacity enhancement with attendant costs on infrastructure development. The adoption of emerging Next Generation Network techniques coupled with Fixed Mobile Convergence (FMC) could alleviate the problems to a large extent. The FMC concept for spectrum saving is based on the concept of utilization of an existing resource in the form of fixed telephone lines for diverting the traffic on mobile networks in scenarios where such diversion will not affect the user service requirements. The enabling technologies that can lead to FMC have also been identified from user’s perspective. A mathematical model has been developed to estimate the amount of spectrum that can be saved through FMC. Parametric analysis has been carried out with respect to the parameters, which influence the spectrum saving. The model has been applied on real life networks to demonstrate the percentage of spectrum that can be saved. The spectrum thus saved can be used for increasing the number of mobile users without any addition to the existing mobile network infrastructure.

Robust Feature Vector Set Using Higher Order Autocorrelation Coefficients

In this paper, a feature extraction method that is robust to additive background noise is proposed for automatic speech recognition. Since the background noise corrupts the autocorrelation coefficients of the speech signal mostly at the lower orders, while the higher-order autocorrelation coefficients are least affected, this method discards the lower order autocorrelation coefficients and uses only the higher-order autocorrelation coefficients for spectral estimation. The magnitude spectrum of the windowed higher-order autocorrelation sequence is used here as an estimate of the power spectrum of the speech signal. This power spectral estimate is processed further by the Mel filter bank; a log operation and the discrete cosine transform to get the cepstral coefficients. These cepstral coefficients are referred to as the Differentiated Relative Higher Order Autocorrelation Coefficient Sequence Spectrum DRHOASS. The authors evaluate the speech recognition performance of the DRHOASS features and show that they perform as well as the MFCC features for clean speech and their recognition performance is better than the MFCC features for noisy speech.

Special FIR and IIR BI Notch Filters

A methodology for designing FIR bi notch filters derived from second order prototype IIR notch filters is suggested. A special case when two notch frequencies ω1 and ω2 are such that [(cos ω1)(cos ω2) = -1/2] has been discussed. The IIR bi notch filter design for this special case results reduction in the number of multipliers without affecting the response of the desired notch filter. For the referred condition, the required design weights of FIR bi notch filter reduce to almost half in number resulting in reduced computations.