Linear FIR Research Articles

An Implementation of FIR Filter by FPGA Used onSAR Preprocessing Filter

In the real-time processing system of Synthetic Aperture Radar, the preprocessor play a very important role and the main component of the preprocessor is FIR filter. As for the requirements of the Synthetic Aperture Radar's preprocessing filter, this paper proposes a method of FPGA based FIR filter design by linear FIR digital filter window function and accomplished a 16-tap 8-bit FIR filter by using XCV100E FPGA devices. As for the key technical problem-the multipliers, we give the Distributed Arithmetic which converts the multiplications into some look-up operations. This arithmetic uses the LUT resources in the FPGA fully and can improve the system's speed and system's reliability. The design method is very useful for the accomplishment of real-time processor of SAR and will benefit the space-borne Synthetic Aperture Radar real-time processing system. The results of simulation on the hardware circuit prove this method is efficient and can meet the design requirements very well.

Design of optimal linear phase FIR high pass filter using craziness based particle swarm optimization technique

In this paper, an optimal design of linear phase digital high pass FIR filter using Craziness based Particle Swarm Optimization (CRPSO) approach has been presented. FIR filter design is a multi-modal optimization problem. The conventional gradient based optimization techniques are not efficient for such multi-modal optimization problem as they are susceptible to getting trapped on local optima. Given the desired filter specifications to be realized, the CRPSO algorithm generates a set of optimal filter coefficients and tries to meet the desired specifications. In birds’ flocking or fish schooling, a bird or a fish often changes directions suddenly. This is described by using a ‘‘craziness’’ factor and is modeled in the CRPSO technique. In this paper, the realizations of the CRPSO based optimal FIR high pass filters of different orders have been performed. The simulation results have been compared to those obtained by the well accepted classical optimization algorithm such as Parks and McClellan algorithm (PM), and evolutionary algorithms like Real Coded Genetic Algorithm (RGA), and conventional Particle Swarm Optimization (PSO). The results justify that the proposed optimal filter design approach using CRPSO outperforms PM, RGA and PSO, in the optimal characteristics of frequency spectrums.

MINLIP for the identification of monotone Wiener systems

This paper studies the MINLIP estimator for the identification of Wiener systems consisting of a sequence of a linear FIR dynamical model, and a monotonically increasing (or decreasing) static function. Given T observations, this algorithm boils down to solving a convex quadratic program with O ( T ) variables and inequality constraints, implementing an inference technique which is based entirely on model complexity control, a technique which is dubbed as Einstein’s razor. 2 2 This is a rewritten, refined and an extended version of the accepted CDC 2010 submission ‘On the Identification of Monotone Wiener Systems’. This technique is proven to yield, here, almost consistent estimates in case the given data is suitably rich (local Persistently Exciting of sufficient order), and if the samples obey a ‘true’ monotone Wiener system satisfying some regularity conditions. It is then indicated how to extend the method in order to cope with noisy data, and empirical evidence is given in order to support the claim of efficiency.

Automatic Tuning of the Pulse-Step Model Predictive Controller

AbstractThis paper describes an autotuning procedure for single-loop model based predictive controller with manipulated value constraints focused on applications in process control. It is assumed that the controlled process is stable, linear and t-invariant FIR system described by three-parameter model derived from a simple identification experiment. Controller parameters are computed from the identified model. A single parameter intended for fine-tuning of the controller is available. Exact intervals are given to vary this parameter within.

A linear FIR filter satisfying power complementary property

A linear FIR filter satisfying power complementary property

Least-Squares Design of Variable Maximally Linear FIR Differentiators

In this correspondence, the design of variable maximally linear (VML) FIR differentiators by least-squares method is proposed. The VML differentiator is designed such that its maximally flat frequency is adjustable. The used transfer function is formulated in a variable frame, and the Farrow structure can be applied for the implementation of VML FIR differentiators. For comparison, the non-variable optimal design of maximally linear FIR differentiators is also proposed. The experiments show that the variable design indeed possesses the flat characteristics as the independent optimal design.

Direct Linearization of Weakly Nonlinear Volterra Systems Using Adaptive Linear and Nonlinear FIR Filters

Linearization of nonlinear systems is a very important topic in many practical applications. The linearization scheme of Gao and Snelgrove (1990) for weakly nonlinear Volterra systems using adaptive linear and nonlinear FIR filters is considered in this paper. The coefficients of these filters can be indirectly estimated using the Least Mean Squares (LMS) and Recursive Prediction Error Method (RPEM) algorithms as done in Gan and Abd-Elrady (2008b). In this paper, these coefficients are directly estimated using the Nonlinear Filtered-x Least Mean Squares (NFxLMS) algorithm and the Spectral Magnitude Matching (SMM) method. Simulation study shows that the suggested direct approaches can significantly suppress spectral regrowth and reduce nonlinear distortion as well as the indirect approach.

Simple Pulse-Step Model Predictive Controller

This paper describes a novel simple model based predictive controller with manipulated value constraints. This controller is suitable for substitution of the classical PID controller used in industrial practice. It is assumed that the controlled system is stable, linear and t-invariant FIR system. The discrete step response sequence is used as the process model. Alternatively it is possible to use three-parameter model. To make the open-loop optimization easier the set of admissible control sequences is restricted to stepwise pulse-step sequences. The optimization procedure is then executable in reasonable time. A single tuning parameter is available for manual fine-tuning of the controller - the control moves penalty coefficient.

MPOE Based Prefiltering and MRT Beamforming with Matched Filter Receiver for DS-CDMA Systems

In order to reduce the complexity of the mobile receiver, we develop two prefilter models using a linear FIR prefilter for minimizing the probability of error in multi-user transmission scenario. We consider downlink transmission. In the first system model, we have a single common prefilter for all users at the base station transmitter and in the second system model, we consider an individual prefilter for each and every user. We assume complete knowledge of the channel at the base station. In order to fully utilize the knowledge available at the transmitter, the filter weights are computed, conditioned on the transmitted bit vector sequence. This also makes the computation of the prefilter coefficients linear in the number of users as opposed to the exponential complexity otherwise. Coefficients of FIR prefilter are computed by minimizing the conditional probability of error and the mean square error. To further improve the performance of the proposed models, we consider Maximum Ratio Transmission (MRT) beamforming at the base station for both the models. Simulation results illustrate the performance of the proposed system models.

Development and Manufacture of a Linear 16-Pixel FIR Array—The PACS Module

The high- and low-stressed photodetector array camera and spectrometer (PACS) modules (linear 16-pixel arrays) are the basic constituents of the 16 × 25 pixel far-infrared (57–220 μm) PACS cameras aboard the Herschel satellite. The essentials for the stress application and the pixel stacking technique originate from detectors aboard the Infrared Space Observatory (ISO, 1995–1998) and for the field imaging far infrared line spectrometer (FIFI-LS) aboard the Stratospheric Observatory for Infrared Astronomy (SOFIA). To meet the mass budget of the cameras and provide the required high tensile strength, the only usable material for the module body turned out to be an aluminum alloy (AL 7075 T651). Especially challenging was the tight thermal budget for the PACS modules. Compared to FIFI-LS, in the case of the PACS module the heat dissipation from the front end electronics (FEE) and harness substrates at about 4 K to the module body containing the pixel stack at about 2 K had to be reduced drastically. A genuine suspension concept and packaging for the respective substrates was developed and successfully applied, allowing reliable electrical wiring from the harness over the FEE on to the pixels. The FEE with the cryogenic readout electronics (CRE) is contributed by the Interuniversity Microelectronics Centre (IMEC).

FIR Zero-Forcing Multiuser Detection and Code Designs for Downlink MC-CDMA

This paper focuses on multiuser detection for multicarrier code-division multiple-access (MC-CDMA) systems, employing cyclic-prefixed (CP) or zero-padded (ZP) transmission techniques. For both systems, we consider either the classical linear finite-impulse response (L-FIR) receiving structures or, when the transmitted symbols are improper, the proposed widely linear FIR (WL-FIR) ones, which process both the received signal and its complex-conjugate version. With regard to both CP- and ZP-based downlink configurations, it is shown that, if the number of users does not exceed a given threshold and their codes are appropriately designed, L-FIR and WL-FIR universal zero-forcing (ZF) multiuser detectors can be synthesized, which, in the absence of noise, guarantee perfect symbol recovery for each user, regardless of the underlying frequency-selective channel. In particular, some spreading code examples are provided, which satisfy the design rules. Finally, numerical simulations are carried out to show that the theoretical considerations developed herein provide useful guidelines for practical MC-CDMA system designs.

Acoustic detection of North Atlantic right whale contact calls using spectrogram-based statistics

This paper considers the problem of detection of contact calls produced by the critically endangered North Atlantic right whale, Eubalaena glacialis. To reduce computational time, the class of acceptable detectors is constrained by the detectors implemented as a bank of two-dimensional linear FIR filters and using the data spectrogram as the input. The closed form representations for the detectors are derived and the detection performance is compared with that of the generalized likelihood ratio test (GLRT) detector. The test results demonstrate that in the presence of impulsive noise, the spectrogram-based detector using the French hat wavelet as the filter kernel outperforms the GLRT detector and decreases computational time by a factor of 6.

Modeling atmospheric turbulence as a filter for sonic boom propagation

Atmospheric turbulence is known to alter the pressure waveform created by supersonic flight. It is challenging to predict how a particular sonic boom waveform will be affected by a particular atmospheric realization without performing intense atmospheric modeling calculations. This paper attempts to approximate the effects of turbulence as a linear FIR filter. Such a filter is estimated from real sonic boom data measured on the ground and at altitude.

Bilinear equation method for unbiased identification of linear FIR systems in the presence of input and output noises

The presence of contaminating noises in both the input and output of an FIR system usually results in a biased least squares (LS) parameter estimate. The total least squares (TLS) methods are known to be efficient in achieving unbiased estimation, if the ratio of the input noise variance to the output noise variance (NNR) is known. However, when the NNR is unknown, a simple analysis shows that the classical LS and TLS estimation methods usually have such insufficient degree of freedom that they can achieve the unbiased solution. In this paper, it is shown by analyzing the algebraic structure of the correlation matrix that the unbiased estimate of FIR parameters can be obtained by solving a special bilinear equation. Then we develop a bilinear equation method (BEM) for solving the bilinear equation associated with the unbiased solution of the FIR system or filtering under the unknown NNR. Unlike the available unbiased estimators, the main advantage is that the proposed method exploits much sufficiently the special structure of the correlation matrix and obtains much accurate estimation for FIR filtering in the presence of input and output noises. Two simulation examples are presented that show the good performance of the proposed method, including its superiority over the classical LS and TLS approaches, and the instrumental variable methods.

FIR Lattice Structures with Single Multiplier Sections

An alternative derivation is given for the linear prediction FIR lattice structures with single-multiplier sections. As compared to the previous approaches, this method is believed to be conceptually simpler and more straightforward.

Influence of advanced electromyogram (EMG) amplitude processors on EMG-to-torque estimation during constant-posture, force-varying contractions

Numerous studies have investigated the relationship between surface electromyogram (EMG) and torque exerted about a joint. Most studies have used conventional EMG amplitude (EMGamp) processing, such as rectification followed by low-pass filtering, to pre-process the EMG before relating it to torque. Recently, advanced EMGamp processors that incorporate signal whitening and multiple-channel combination have been shown to significantly improve EMGamp processing. In this study, we compared the performance of EMGamp–torque estimators with and without these advanced EMGamp processors. Fifteen subjects produced constant-posture, non-fatiguing, force-varying contractions about the elbow while torque and biceps/triceps EMG were recorded. EMGamp was related to torque using a linear FIR model. Both whitening and multiple-channel combination reduced EMG–torque errors and their combination provided an additive benefit. Using a 15th-order linear FIR model, EMG–torque errors with a four-channel, whitened processor averaged 7.3% of maximum voluntary contraction (MVC) (or 78% of variance accounted for). By comparison, the equivalent single-channel, unwhitened (conventional) processor produced an average error of 9.9% of MVC (variance accounted for of 55%). In addition, the study describes the occurrence of spurious peaks in estimated torque when the torque model is created from data with a sampling rate well above the bandwidth of the torque. This problem occurs when the torque data are sampled at the same rate as the EMG data. The problem is corrected by decimating the EMGamp prior to relating it to joint torque, in our case to an effective sampling rate of 40.96 Hz.

Design Method for 2-Channel Signal Word Decomposed Filters with Minimum Output Error and Their Effective VLSI Implementation

This paper proposes hardware-efficient VLSI architectures for 2-channel signal word decomposed filters (2-ch SWDFs) and their design method in consideration of the implemented circuit size. By consideration of the circuit size in design method, 2-ch SWDFs with a minimum output error among SWDFs whose size is equal to or smaller than a specification can be designed. Canonical Signed Digit expressions are used to effectively represent the filter coefficients of the SWDFs in order to make its circuit size small. Through precise analysis of the internal structures, circuit size can be accurately estimated. Some design examples show that the proposed method can design filters whose output error is about -12 dB lower than that of the linear FIR filters. Compared to an exhaustive search method, our method is much faster and can design filters whose output errors are only about 2 dB more.

Low-complexity search for optimal delay in linear FIR MMSE equalization

In this letter, an efficient algorithm to determine the optimal delay in linear finite impulse response equalizers based on the minimum mean-square-error criterion is proposed. The algorithm uses the Levinson-Durbin (L-D) recursion as a starting point to find the values of the mean-square error for equalizers with all nontrivial delays. Despite the exhaustive search approach, the complexity of the proposed algorithm is only doubled when compared to the calculation of the equalizer with one prescribed delay. Such increase in complexity may be fully justified in practice because it yields globally optimal equalizer's design.

The Cramer-Rao Bound and DMT Signal Optimisation for the Identification of a Wiener-Type Model

In linear system identification, optimal excitation signals can be determined using the Cramer-Rao bound. This problem has not been thoroughly studied for the nonlinear case. In this work, the Cramer-Rao bound for a factorisable Volterra model is derived. The analytical result is supported with simulation examples. The bound is then used to find the optimal excitation signal out of the class of discrete multitone signals. As the model is nonlinear in the parameters, the bound depends on the model parameters themselves. On this basis, a three-step identification procedure is proposed. To illustrate the procedure, signal optimisation is explicitly performed for a third-order nonlinear model. Methods of nonlinear optimisation are applied for the parameter estimation of the model. As a baseline, the problem of optimal discrete multitone signals for linear FIR filter estimation is reviewed.

A Weighted Least-Square-Based Approach to FIR Filter Design Using the Frequency-Response Masking Technique

This paper presents a new method for the design of sharp linear phase FIR filters using the frequency-response masking (FRM) technique. The method is based on a weighted least square (WLS) approach, and the design problem is solved iteratively. The original least square (LS) problem is decomposed into two LS problems, each of which can be solved analytically. The effectiveness of the method is demonstrated through the design of a lowpass linear phase sharp FIR digital filter.