Frequency Response Masking Technique Research Articles

A Computationally Efficient 11 Band Non-Uniform Filter Bank for Hearing Aids Targeting Moderately Sloping Sensorineural Hearing Loss

A computationally efficient 11 band non-uniform filter bank addressing low or moderately sloping sensorineural hearing loss - the most common type of hearing problem- is proposed. This structure is suitable for low cost, small area implementations of hearing aids. The computational efficiency is achieved by adopting the Frequency Response Masking technique, which uses only two prototype filters with a total of 19 multipliers at 80dB stopband attenuation for the design of entire non-uniform filter bank. The computational complexity analysis shows that the proposed method provides about a 70-90% reduction in computational resources compared to non-FRM methods and about a 40-80% reduction in computational resources compared to the other FRM methods. The audiogram matching performance analysis shows that the matching error of the proposed filter bank is negligible even without optimization. The delay performance of the filter bank is acceptable for both Closed Canal Fittings and Open Canal Fittings.

Design of Computationally Efficient Sharp FIR Filter Utilizing Modified Multistage FRM Technique for Wireless Communications Systems

Modern wireless communications gadgets demand multi-standard communications facilities with least overlap between different input radio channels. A sharp digital filter of extremely narrow transition-width with lower stop band ripples offers alias-free switching among the preferred frequency bands. A computationally competent low pass filter (LPF) structure based on the multistage frequency response masking (FRM) approach is proposed for the design of sharp finite impulse response (FIR) filters which are suitable for wireless communications applications. In comparison of basic FRM with other existing multistage FRM structures, the proposed structure has a narrow transition bandwidth and higher stop band attenuation with significant reduction in terms of the number of computational steps. A design example is incorporated to demonstrate the efficiency of the proposed approach. Simulation results establish the improvement of the proposed scheme over other recently published design strategies.

A Class of IIR Filters Synthesized Using Frequency-Response Masking Technique

This letter presents a class of infinite impulse response (IIR) filters synthesized using a system of IIR subfilters based on the frequency-response masking (FRM) technique. In the proposed class of filters, the bandedge shaping filters are a parallel connection of two allpass filters, and the masking filters are approximately linear phase IIR filters composed of a parallel connection of a delay line and an allpass filter. A design method which jointly optimizes the IIR subfilters is introduced. The proposed class of IIR filters has lower coefficient sensitivity and roundoff noise compared with conventional IIR filters.

Frequency response masking based FIR filter using approximate multiplier for bio-medical applications

The advancements in medical healthcare networks and bio-medical sensor technologies enabled the use of wearable and body implantable intelligent devices for healthcare monitoring. These battery-operated devices must be capable of very low power operation for ensuring long battery life and also to prevent intense radiations. The major power consuming part of these devices are the multipliers built into the digital filters for performing signal processing operations. This paper proposes a low power signed approximate multiplier architecture for bio-medical signal processing applications. The circuit characteristics and error metrics of the proposed multiplier are estimated to verify its performance advantage over other approximate multipliers. In order to validate the efficacy of the approximate multiplier in real time signal processing applications, a band pass finite impulse response filter (FIR) filter is designed using frequency response masking technique and used in the Pan Tompkins method for the extraction of QRS complex from raw ECG data. The sensitivity, positive predictivity, and detection error rate of the QRS detection method are estimated and the results show that the approximate filtering method implemented gives a comparable performance as that of exact methods.

Design of Power Efficient Variable Bandwidth Non-Maximally Decimated FRM Filters for Wideband Channelizer

In this brief, a power efficient reconfigurable non-maximally decimated filter bank-based modified frequency response masking technique is proposed to generate sharp transition width channels for wideband applications. The structure enables cost and power efficient processing of wideband signals. The main benefit of the proposed scheme is that the computational workload and hardware complexity of the modified frequency response masking technique is considerably less than that of the approaches existing in the literature. The hardware complexity of the design is further reduced by joint optimization of all the canonical signed digit represented filters using Pareto-based meta-heuristic algorithm.

Design of Pipelined IIR Filters Using Two-Stage Frequency-Response Masking Technique

A pipelined, high-speed infinite impulse response (IIR) filter based on the frequency-response masking (FRM) technique has been proposed by Johansson and Wanhammar. In their method, the bandedge shaping filters are a pair of IIR power complementary filters whose ${z}$ -transform functions are functions of ${z} ^{M}$ and the masking filters are linear phase finite impulse response (FIR) filters. The IIR bandedge shaping filters have $M$ delays in the feedback loop and can be pipelined by ${M}$ stages. In this brief, we present a two-stage FRM method for reducing the number of multipliers of the pipelined IIR filter proposed by Johansson and Wanhammar for a given magnitude response specification and a given number of pipeline stages in the feedback loop. In our design, all the subfilters are optimized jointly. We show that our two-stage masking design requires fewer multipliers if the number of pipeline stages in the feedback loop is larger than four.

The Design of Low-Power 16-Band Nonuniform Filter Bank for Hearing Aids.

A computationally efficient, low-power (107.6 μW@1.1V), small core area (2.82[Formula: see text]@0.35 μm), 16-band nonuniformly spaced digital filter bank with stop-band attenuation of more than 60dB is designed and implemented for hearing aid applications using a 0.35 μm CMOS process. The low computational complexity of the filter bank is achieved using a frequency response masking technique with multiple band-edge shaping filters. The proposed filter bank yields significant improvements in both power consumption and group delay. By coefficient sharing scheme, the implementation of such a filter bank requires only three multipliers.

Removal of Baseline Wander Noise in ECG Signal Using Asymmetrical Frequency-Response Masking Bandpass Filters.

FIR filter is one of the best choices for ECG signal processing because of its linear phase property. With frequency response masking (FRM) technique, the multipliers needed to implement FIR filter can be reduced dramatically. This paper proposes an architecture for asymmetrical bandpass FIR filter based on the FRM technique. The optimum interpolation factor for the filter is derived and the design procedure for all the sub-filters is given. A design example is included to illustrate the effectiveness of the proposed filter for ECG signal processing. It shows that the filter can fulfill the design objectives with 70.3% less multipliers comparing to the conventional FIR synthesizing technique.

Low complexity reconfigurable channelizers using non-uniform filter banks

A Software Defined Radio (SDR) channelizer needs reconfigurable sharp filter banks with low implementation complexity. In this paper, the design of non-uniform Modified Discrete Fourier Transform filter bank (MDFT FB) is proposed to be used in SDR channelizer. The frequency response masking technique is used to design the prototype filter which gives sharp filters with lower hardware complexity, compared to the finite impulse response filters. The canonic signed digit (CSD) representation is used in the design, to convert the continuous filter coefficients into discrete coefficients. Multi-objective artificial bee colony algorithm is utilized to improve the performance degradation when the CSD represented filter coefficients are used. Further, the shift inclusive differential technique with common sub-expression elimination is used to reduce the number of adders. Xilinx ISE is used to verify the hardware requirement, for the implementation of the non-uniform MDFT FB. Hence low complexity reconfigurable SDR channelizers using non-uniform MDFT FB is proposed in this paper.

Efficient uniform digital filter bank with linear phase and FRM technique for hearing aids

This paper attempts to present an uniform digital filter bank based on linear phase FIR and IIR filters applied for Frequency Response Masking (FRM) technique in hearing aid applications.In the proposed filter bank, nine uniformly spaced sub-bands are formed with the help of half band filters and masking filters. These nine channel FIR filter bank is realized using an interpolated half band linear phase FIR filter and an appropriate number of masking FIR filters. The nine channel IIR filter bank is realized using an interpolated half band approximately linear phase IIR filter and an appropriate number of masking filters. The proposed approximately linear phase IIR half band filter bank is compared with filter bank based on linear phase FIR half band filters in terms of area, power, memory and number of gates needed for implementation. The experiment was carried on various hearing loss cases and the results obtained from these tests proves that, the proposed filter bank achieved the required matching between audiograms and magnitude response of the filter bank at very reasonable range with less computational complexity.

On the Implementation of Time-Multiplexed Frequency-Response Masking Filters

The complexity of narrow transition band FIR filters is high and can be reduced by using frequency-response masking (FRM) techniques. These techniques use a combination of periodic model filters and, possibly periodic, masking filters. Time-multiplexing is in general beneficial since only rarely does the technology bound maximum obtainable clock frequency and the application determined required sample rate correspond. Therefore, architectures for time-multiplexed FRM filters that benefit from the inherent sparsity of the periodic filters are introduced in this paper. We show that FRM filters not only reduce the number of multipliers needed, but also have benefits in terms of memory usage. Despite the total amount of samples to be stored is larger for FRM, it results in fewer memory resources needed in FPGAs and more energy efficient memory schemes in ASICs. In total, the power consumption is significantly reduced compared with a single-stage implementation. Furthermore, we show that the choice of the interpolation factor that gives the least complexity for the periodic model filter and subsequent masking filter(s) is a function of the time-multiplexing factor, meaning that the minimum number of multipliers not always corresponds to the minimum number of multiplications. Both single-port and dual-port memories are considered, and the involved tradeoff in number of multipliers and memory complexity is illustrated. The results show that, for FPGA implementation, the power reduction ranges from 23% to 68% for the considered examples.

Design of FRM-based MDFT filter banks in the canonic signed digit space using modified meta-heuristic algorithms

An optimal totally multiplier-less sharp transition width Modified Discrete Fourier Transform (MDFT) filter bank is proposed in this work. Since, here, the aim is to design a low complexity sharp transition width MDFT filter bank, the filters of the filter bank are designed using Frequency Response Masking technique to reduce the number of multipliers and hence the complexity. To replace multipliers with adders and shifters, the filter coefficients are converted into the Canonic Signed Digit space. In order to reduce the number of adders and shifters in the multiplier-less implementation, restricted number of non-zero bits is used in the conversion. This may degrade the performances of the MDFT filter bank. The performances are improved using modified meta-heuristic algorithms. A new hybrid algorithm which combines the qualities of Harmony Search Algorithm and Gravitational Search Algorithm is proposed in this work to optimise the performance of the MDFT filter bank.

A Novel Approach to Design Low-Cost Two-Stage Frequency-Response Masking Filters

The multistage frequency-response masking (FRM) technique is widely used to reduce the complexity of a filter when the transition bandwidth is extremely small. In this brief, a real generalized two-stage FRM filter without any constraint on the subfilters or the interpolation factors was proposed. New principles and equations were deduced to determine the design parameters. The subfilters were then jointly optimized using nonlinear optimization. Experiential results show that when the proposed algorithm obtains different solutions with the conventional algorithm, the solution of the proposed approach is better with less number of filter coefficients and sometimes with lower delay as well than the conventional two-stage FRM, which can lead to a reduced hardware cost in applications.

Combined FRM and GDFT filter bank designs for improved nonuniform DSA channelisation

AbstractMultistandard channelisation for base stations is a big application of generalised discrete Fourier transform modulated filter banks (GDFT‐FBs) in digital communications. For technologies such as software‐defined radio and cognitive radio, nonuniform channelisers must be used if frequency bands are shared by different standards. However, GDFT‐FB‐based nonuniform channelisers can suffer from high filter orders when applied to wideband input signals. In this paper, various combinations of GDFT‐FB with the frequency response masking technique are proposed and evaluated for both uniform and nonuniform channelisation applications. Results show that the proposed techniques achieve savings in both the number of filter coefficients and the number of operations per input sample. Copyright © 2015 John Wiley & Sons, Ltd.

Design of low complexity sharp MDFT filter banks with perfect reconstruction using hybrid harmony-gravitational search algorithm

The design of low complexity sharp transition width Modified Discrete Fourier Transform (MDFT) filter bank with perfect reconstruction (PR) is proposed in this work. The current trends in technology require high data rates and speedy processing along with reduced power consumption, implementation complexity and chip area. Filters with sharp transition width are required for various applications in wireless communication. Frequency response masking (FRM) technique is used to reduce the implementation complexity of sharp MDFT filter banks with PR. Further, to reduce the implementation complexity, the continuous coefficients of the filters in the MDFT filter banks are represented in discrete space using canonic signed digit (CSD). The multipliers in the filters are replaced by shifters and adders. The number of non-zero bits is reduced in the conversion process to minimize the number of adders and shifters required for the filter implementation. Hence the performances of the MDFT filter bank with PR may degrade. In this work, the performances of the MDFT filter banks with PR are improved using a hybrid Harmony-Gravitational search algorithm.

Design of totally multiplier-less sharp transition width tree structured filter banks for non-uniform discrete multitone system

In this paper, a multiplier-less near perfect reconstruction tree structured non-uniform filter bank for discrete multitone (DMT) system is proposed. In DMT systems, filters with sharp transition width are required to reduce the inter-channel interference. When sharp transition width filter banks are to be implemented, the order of the filters will become very high. Frequency response masking technique is known to result in filters with sharp transition width with less complexity. To further reduce the complexity and power consumption, the filter bank is made totally multiplier-less by converting the continuous filter coefficients to finite precision coefficients in the canonic signed digit space. This may lead to performance degradation and calls for the use of suitable optimization techniques. Here, the search space consists of only integers. Hence, meta-heuristic algorithms are preferred as they can be tailor made to suit the problem under consideration. In this work, meta-heuristic algorithms such as, artificial bee colony, harmony search and gravitational search are deployed to improve the performance of the tree structured filter bank. Thus, the proposed method results in tree structured non-uniform filter banks which are simple, multiplier-less and have linear phase, sharp transition width, very low aliasing and reduced amplitude distortion.

Prototype Filter Design Approaches for Near Perfect Reconstruction Cosine Modulated Filter Banks - A Review

Cosine Modulated Filter Banks (CMFB) are very popular among the different maximally decimated filter banks due to their design ease and simplicity in implementation and the property that all the coefficients of all the filters are real. All the analysis and synthesis filters are derived from one or two prototype filters. Hence, recently, the design of the prototype filter in a CMFB has become a subject of interest in the field of multirate signal processing. Perfect Reconstruction (PR) filter banks are those which can produce at the output, a weighted delayed version of the input. But in most of the applications a near perfect reconstruction (NPR) is sufficient. This can reduce the computational complexity. Different approaches developed for the efficient and optimal design of the prototype filter in a NPR orthogonal CMFB are studied, classified and summarized in this paper. In today's applications, less space and low power consumption are very essential. When the different design approaches for the design of the prototype filter in CMFB are compared, it is observed that the one using frequency response masking(FRM) and meta-heuristic optimization techniques gives better performance in terms of implementation complexity, which in turn can lead to reduced chip size and power consumption. It is hoped that this review will be highly beneficial to the researchers working in the area of multirate signal processing. At the end, we also propose some novel design approaches for the design of low complexity prototype filter using FRM technique.

Reducing Complexity of FIR Filters using Narrowband Filters

Reducing complexity of FIR filters using narrowband filters presents a practically efficient Narrowband FIR Filter designed by using Frequency Response Masking Technique & the Interpolated FIR technique. The Proposed method cascades the interpolated filter with masking filter. By giving the filter design coefficients (filter characteristics) we can determine the filters interpolated magnitude coefficients. & then this is given to Narrowband Filter will get the impulse response with less number of taps. At the last step we can remove the unwanted part by using the masking filter. LabVIEW software is used to implement the reduced complexity FIR filter using narrowband filter. It was shown that the resulting filter is practically efficient and also the errors in human Audiogram are minimized. General Terms Sampling Frequency, Ripple Factor, Attenuation, Pass-band, Stop-band.

Improved Design of Frequency-Response Masking Filters Using Band-Edge Shaping Filter With Non-Periodical Frequency Response

Frequency-Response Masking (FRM) technique has been widely used in all kinds of applications where FIR filters with extremely narrow transition band are needed. Thus, researchers have invested much effort to find ways to increase the efficiency of the FRM algorithm. In this paper, a novel 2-stage FRM structure was proposed. The three interpolation factors of the subfilters in the second stage can be chosen independently. The band-edge shaping filter synthesized by the second stage has a non-periodical frequency response, which is quite different from conventional FRM structures. Various filters were designed to test the performance of the proposed method. Experiments show that the proposed structure achieves lower complexity, in terms of the number of multipliers, compared to the FRM algorithms such as 1-stage FRM, 2-stage FRM, IFIR-FRM, SFFM-FRM, serial-masking FRM and some current FRM structures.

Design of first-order differentiator utilising FIR and IIR sub-filters

In this paper, we propose a novel approach for constructing the first-order differentiator. It has been shown recently that an efficient Finite Impulse Response (FIR) wideband differentiator can be synthesised when applying the multirate and Frequency-Response Masking (FRM) techniques. The overall signal processing task is shared between a very low- order differentiator and an FIR half-band filter. The novelty of this paper is the usage of an approximately linear-phase IIR half-band filter based on the parallel connection of all-pass sub- filter and pure delay. The structure of resulting wideband differentiator consists of the approximately linear phase all-pass sub-filter, two low-order FIR polyphase sub-filters, and the delay element. The knowledge-based design has been used for the analysis and improvements of the wideband differentiator. The proposed system provides computational savings and exhibits a significantly smaller overall delay if compared with the corresponding solution based on FIR filters only.