Department of Electrical Engineering

Indian Institute of Technology Palakkad&nbsp;(IIT Palakkad or IIT PKD) is a public autonomous&nbsp;engineering&nbsp;and&nbsp;research&nbsp;institute located in&nbsp;Palakkad,&nbsp;Kerala. It was&nbsp;one of the five new&nbsp;IITs&nbsp;proposed in the&nbsp;2014 Union budget of India. The campus was inaugurated on 3 August 2015. The institute has 94 faculty, 978 students, and 63 non-teaching staffs.

IT Palakkad currently offers four-year Bachelor of Technology (B.Tech) and two years MS programmes in 8 different engineering disciplines including&nbsp;Computer Science, Electrical, Mechanical, Civil among others.

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IIT Palakkad

The ability to support multiple channels of different communication standards, in the available bandwidth, is of importance in modern software defined radio (SDR) receivers. An SDR receiver typically employs a channelizer to extract multiple narrowband channels from the received wideband signal using digital filter banks. Since the filter bank channelizer is placed immediately after the analog-to-digital converter (ADC), it must operate at the highest sampling rate in the digital front-end of the receiver. Therefore, computationally efficient low complexity architectures are required for the implementation of the channelizer. The compatibility of the filter bank with different communication standards requires dynamic reconfigurability. The design and realization of dynamically reconfigurable, low complexity filter banks for SDR receivers is a challenging task. This paper reviews some of the existing digital filter bank designs and investigates the potential of these filter banks for channelization in multi-standard SDR receivers. We also review two low complexity, reconfigurable filter bank architectures for SDR channelizers based respectively on the frequency response masking technique and a novel coefficient decimation technique, proposed by us recently. These filter bank architectures outperform existing ones in terms of both dynamic reconfigurability and complexity. © 2008 Springer Science+Business Media, LLC.

World University root node

Journal of Signal Processing Systems

Filter bank channelizers for multi-standard software defined radio receivers

Thermodynamic properties of the troposphere, particularly water vapor content and temperature, change in response to physical mechanisms, including frictional drag, evaporation, transpiration, heat transfer, pollutant emission and flow modification due to terrain. The planetary boundary layer (PBL) is characterized by a greater rate of change in its thermodynamic state than higher tropospheric altitudes. Such changes in the PBL typically occur on time scales of less than one hour; whereas the upper troposphere exhibits much longer time constants. Large horizontal gradients in vertical wind speed and steep vertical gradients in water vapor and temperature in the PBL result in high-impact weather, including severe thunderstorms. Observation of these gradients in the PBL with improved vertical resolution is important for improvement of weather prediction. Additionally high vertical resolution and accuracy of measured thermodynamic profiles, especially water vapor and temperature, are important for initialization of numerical weather prediction models. Satellite remote sensing in the visible, infrared and microwave bands provides qualitative and quantitative measurements of many atmospheric properties, including cloud cover, precipitation, liquid water content and precipitable water vapor in the atmosphere above the PBL. However, its ability to characterize thermodynamic properties of the PBL is limited by the confounding factors of ground emission in microwave channels and of cloud cover in visible and IR channels, as well as limitations in the vertical resolution of the remote sensing instruments onboard the satellite. Ground-based microwave radiometers are routinely used to estimate thermodynamic profiles, but the accuracy and resolution of vertical profiles may be improperly estimated. Here a new technique has been used to improve the vertical resolution of retrieved water vapor density profiles, based on the design of the Compact Microwave Radiometer for Humidity Profiling (CMR-H) [1]. The CMR-H operates at four frequencies near the weak water vapor absorption line, namely 22.12, 22.67, 23.25, and 24.5 GHz. © 2011 IEEE.

2011 30th URSI General Assembly and Scientific Symposium, URSIGASS 2011

Trade-off between vertical resolution and accuracy in water vapor retrievals from ground-based microwave brightness temperature measurements

Over the last decade, Si1-xGex has increasingly been used as a channel material in MOSFETs. Though many studies have dealt with the real bandstructure of Si1-xGex, the effect of germanium mole fraction x on complex bandstructure has been unexplored. Complex bands fundamentally determine band to band tunneling (BTBT) current. For example, using the orientation dependent complex bandstructure of silicon [1], it has been shown [2] that the BTBT current in the [110] direction is an order of magnitude larger than that along the [100] direction. BTBT contributes significantly to off-current Ioff in conventional MOSFETs, via the mechanism of gate induced drain leakage (GIDL). Additionally, BTBT determines the on current Ion in tunneling FETs, which have been suggested as next generation devices. Further, BTBT is more dominant in Si 1-xGex than silicon, owing to a narrower bandgap. In this work, we determine the orientation dependent complex bandstructure of Si 1-xGex along common crystallographic directions and predict trends in BTBT current. © 2011 IEEE.

Device Research Conference - Conference Digest, DRC

Orientation dependent complex bandstructure of Si1-xGe x alloys

Zero-crossing rate (ZCR) is one of the most important acoustic feature that has been widely used in voice activity detection, voiced/unvoiced speech classification, music/speech classification image processing, optics, biomedical engineering, radar and fluid mechanics. The conventional time-domain ZCR measurement is sensitive to nonstationary noise. In this paper, we present a noise robust zerocrossing rate computation method. The number of zerocrossings is computed in autocorrelation-domain rather than in time-domain. The accuracy of the proposed measurement method is evaluated using both sinusoidal and speech waveforms under different signal-to-noise ratios (SNRs). Experimental results show that the proposed ZCR measurement method achieves better accuracy than the conventional ZCR measurement methods in the literature. © 2011 IEEE.

3rd International Conference on Trendz in Information Sciences & Computing …

Noise robust zerocrossing rate computation for audio signal classification

In recent decades, atmospheric scientists have been interested in measuring thermodynamic variables such as tropospheric water vapor and temperature with increasing temporal and spatial resolution due to their importance on the climate modeling. For this purpose, microwave radiometers have been used to measure columnar integrated water vapor. The radiative transfer equation (RTE) has been used to retrieve the contributions of individual atmospheric layers, assuming a stratified atmosphere. In recent years, significant advances have been made toward retrieval of these parameters in 2-D, 3-D and 4-D (3-D + time) distributions. This work presents a new radiometric concept to directly measure the contribution of each pixel (avoiding the use of the RTE inversion) by using pencil-beam antennas and interferometric techniques. This new approach has the potential to improve the quality of the retrieved thermodynamic variables to meet the research goals of atmospheric science. © 2011 IEEE.

International Geoscience and Remote Sensing Symposium (IGARSS)

A radiometer concept to retrieve the 3-D radiometric emission from atmospheric temperature and water vapor density

Spaceborne interferometric synthetic aperture radar (SAR) (InSAR) imaging has been used for over a decade to monitor tectonic movements and landslides, as well as to improve digital elevation models. However, InSAR is affected by variations in round-trip propagation delay due to changes in ionospheric total electron content and in tropospheric humidity and temperature along the signal path. One of the largest sources of uncertainty in estimates of tropospheric path delay is the spatial and temporal variability of water vapor density, which currently limits the quality of InSAR products. This problem can be partially addressed by using a number of SAR interferograms from subsequent satellite overpasses to reduce the degradation in the images or by analyzing a long time series of interferometric phases from permanent scatterers. However, if there is a sudden deformation of the Earth's surface, the detection of which is one of the principal objectives of InSAR measurements over land, the effect of water vapor variations cannot be removed, reducing the quality of the interferometric products. In those cases, high-resolution information on the atmospheric water vapor content and its variation with time can be crucial to mitigate the effect of wet-tropospheric path delay variations. This paper describes the use of a ground-based microwave radiometer network to retrieve 3-D water vapor density with fine spatial and temporal resolution, which can be used to reduce InSAR ambiguities due to changes in wet-tropospheric path delay. Retrieval results and comparisons between the integrated water vapor measured by the radiometer network and satellite data are presented. © 2011 IEEE.

IEEE Transactions on Geoscience and Remote Sensing

Three-dimensional humidity retrieval using a network of compact microwave radiometers to correct for variations in wet tropospheric path delay in spaceborne interferometric SAR imagery

The most computationally demanding block in the digital front-end of a software defined radio (SDR) receiver is the channelizer which operates at the highest sampling rate. Channelizers are employed in the SDR receivers for extracting individual channels (frequency bands) from the digitized wideband input signal. Reconfigurability and low complexity are the two key requirements in an SDR channelizer. A new reconfigurable filter bank (FB) architecture based on frequency response masking (FRM) for SDR channelizers is proposed. The proposed FB offers reconfigurability at the architectural level and at the channel filter level and is capable of extracting channels of nonuniform bandwidths corresponding to multiple wireless communication standards from the digitized wideband input signal. Design examples show that the proposed FB offers multiplier complexity reduction of 84% over the conventional per-channel (PC) approach, which is best suitable for the extraction of channels of nonuniform bandwidth. The proposed FB has been synthesized on 0.18 μm complementary metal oxide semiconductor (CMOS) technology and compared with the PC approach. Synthesis results show that the proposed FB offers area reduction of 85%, power reduction of 48.5%, and improvement in speed of 56.7% over the PC approach. The proposed FB has been implemented on Xilinx Virtex 2v3000ff1152-4 FPGA and tested using real-time inputs from a vector signal generator. © 2006 IEEE.

IEEE Transactions on Aerospace and Electronic Systems

Reconfigurable low area complexity filter bank architecture based on frequency response masking for nonuniform channelization in software radio receivers

In this paper, we present a reliable and efficient automatic R-wave detection based on new nonlinear transformation and simple peak-finding strategy. The detection algorithm consists of four stages. In the first stage, the bandpass filtering and differentiation operations are used to enhance QRS complexes and to reduce out-of-band noise. In the second stage, we introduce a new nonlinear transformation based on energy thresholding, Shannon energy computation, and smoothing processes to obtain a positive-valued feature signal which includes large candidate peaks corresponding to the QRS complex regions. The energy thresholding reduces the effect of spurious noise spikes from muscle artifacts. The Shannon energy transformation amplifies medium amplitudes and results in small deviations between successive peaks. Therefore, the proposed nonlinear transformation is capable of reducing the number of false-positives and false-negatives under small-QRS and wide-QRS complexes and noisy ECG signals. In the third stage, we propose a simple peak-finding strategy based on the firstorder Gaussian differentiator (FOGD) that accurately identifies locations of candidate R-peaks in a feature signal. This stage computes convolution of the smooth feature signal and FOGD operator. The resultant convolution output has negative zero-crossings (ZCs) around the candidate peaks of feature signal due to the anti-symmetric nature of the FOGD operator. Thus, these negative ZCS are detected and used as guides to find locations of real R-peaks in an original signal at the fourth stage. Unlike other existing algorithms, the proposed algorithm does not use search back algorithm and learning phase. The proposed algorithm is validated using the standard MIT-BIH arrhythmia database and achieves an average sensitivity of 99. 94% and a positive predictivity of 99.96%. Experimental results show that the proposed algorithm outperforms other existing algorithms in case of different QRS complex morphologies (negative, low-amplitude, wide), very big change in amplitudes of adjacent R-peaks, irregular heart rates, and noisy ECG signals. © 2011 Biomedical Engineering Society.

Cardiovascular Engineering and Technology

An efficient R-peak detection based on new nonlinear transformation and first-order Gaussian differentiator

This paper proposes a robust and automated applause detection algorithm for meeting speech. The features used in the proposed algorithm are the short-time autocorrelation features such as autocorrelation energy decay factor, amplitude and lag values of first local minimum and zero-crossing points extracted from the autocorrelation sequence of a windowed audio signal. We apply decision thresholds for the above acoustic features to identify applause and non-applause segments from the audio stream. The performance of the proposed algorithm is compared with the conventional method using mel frequency cepstral coefficients (MFCC) feature vectors and Gaussian mixture model (GMM) as classifier. We have also analyzed the performance of these algorithms by varying the number of mixtures in GMM (2, 4, 8, 16 and 32) and various thresholds in the proposed method. The methods are tested with a multimedia database of 4 hours 37 minutes of meeting speech and the results are compared. The precision rate, recall rate and F1 score of the proposed method are 94.40%, 90.75% and 92.54% respectively while those of conventional method are 67.47%, 96.13% and 79.29% respectively. © 2011 IEEE.

2011 3rd International Conference on Electronics Computer Technology

Novel approach for detecting applause in continuous meeting speech

In this paper, we present a new automatic transient detection and localization for analysis of power quality disturbances. The proposed method is based on an over-complete dictionary (OCD) matrix and an ℓ 1-norm minimization algorithm. The OCD matrix is constructed using the spike-like (or identity) bases and discrete-cosine bases. The proposed method is validated using the four types of transient events and the results are compared with wavelet-based method. Experiment results show that the proposed method provides accurate time-information of impulsive and oscillatory transients under high levels of noise, and also preserves signature of transient events. © 2011 IEEE.