Design of nearly perfect reconstructed non-uniform filter bank by constrained equiripple FIR technique

In this paper, an efficient iterative algorithm is proposed for the design of multi-channel nearly perfect reconstructed non-uniform filter bank. The method employs the constrained equiripple FIR technique to design the prototype filter for filter banks with novelty of exploiting a new perfect reconstruction condition of the non-uniform filter banks instead of using complex objective functions. In the proposed algorithm, passband edge frequency (ω_p) is optimized using linear optimization technique such that the filter coefficients values at quadrature frequency are approximately equal to 0.707. Several design examples are included to illustrate the efficacy of this methodology for designing non-uniform filter bank (NUFB). It was found that the proposed methodology performs better as compared to earlier reported results in terms of reconstruction error (RE), number of iteration (NOI) and computation time (CPU time). The proposed algorithm is very simple, linear in nature, and easy to implement.     

过采样NPR DFT调制滤波器组设计

提出了一种具有不同分析和综合原型滤波器的过采样几乎完全重构（NPR）DFT调制滤波器组的更为简单的设计方法。按照滤波器组的通带、阻带、系统失真要求,以系统整体失真误差作为目标函数,分析和综合原型滤波器的阻带能量作为约束条件,同时引入了更简单的通带平坦性约束。与目前的设计方法相比,该方法可以得到性能更好的滤波器组,仿真的结果也证实了这点。     

Prototype filter design for QAM-based filter bank multicarrier system

In this paper, we provide conditions for a prototype filter design of filter bank multicarrier (FBMC) based on quadrature amplitude modulation (QAM). The conditions consist of a generalized Nyquist criterion (GNC) for nearly perfect reconstruction (NPR) and meeting the stopband condition for a small side-lobe. In a practical environment, a small side-lobe is a key aspect of achieving high spectral efficiency, which becomes an important factor in reducing the size of the guard band among channels. In addition, because the conventional GNC is derived under the assumption of an ideal channel, which can be easily broken over a practical multipath channel, we propose a relaxed NPR that considers the multipath delay using a 2L-oversampled discrete Fourier transform (DFT) in the frequency domain. Based on the relaxation of the GNC depending on a multipath channel, we formulate an optimization problem for a QAM-FBMC prototype filter design and propose a prototype filter with a small side-lobe and reliable BER performance. Simulation results show that the proposed prototype filter remarkably reduces the side-lobe compared to conventional QAM-FBMC based on two types of prototype filters and orthogonal frequency division multiplexing (OFDM) via the trade-off between GNC and side-lobe performance. The benefit of the side-lobe condition allows the proposed prototype filter, the Relaxed-NPR-F, to improve spectral efficiency by reducing the guard band in the frequency domain.     

基于QPSO的两通道正交镜像滤波器组的优化设计*

通过分析两通道正交镜像滤波器组的重构条件,提出了一种新的两通道正交镜像滤波器(QMF)组的设计方法,将完全重构的两通道QMF组的设计问题转换为由原型低通滤波器在通带、阻带和过渡带幅频响应的均方误差加权和组成的一种无约束的非线性优化问题,用量子粒子群优化算法(QPSO)来有效求解该类优化问题,获得该问题的全局最优解.最后...     

基于改进离散傅里叶变换调制滤波器组的多载频系统设计

为改善传统正交频分复用(OFDM)多载频系统频率选择性差和频谱泄露等缺陷,研究了基于改进离散傅里叶变换(DFT)调制滤波器组的多载频调制系统设计。将其设计问题归结为一个无约束的最小化调制滤波器组完全重建误差的目标函数优化问题,采用一种改进的窗函数法设计调制滤波器组的原型滤波器和线性优化方法优化目标函数。与传统的窗函数法相比,该改进窗函数法在理想滤波器的过渡带内插了一种样条函数以消除吉布斯效应。仿真结果表明,该方法设计的原型滤波器与传统的平方根升余弦方法设计的原型滤波器和一般矩形窗原型滤波器相比有更高的阻带衰减,对应的改进DFT滤波器组有更小的重建误差。基于该方法设计的改进DFT滤波器组多载频系统在正交相移键控(QPSK)调制和3GPP TS 25.104车载多径信道以及单抽头频域均衡下有更好的误符号率(SER)性能。     

A New Design Approach for Nearly Linear Phase Stable IIR Filter using Fractional Derivative

In this paper,a new design method for digital infinite impulse response(IIR)filters with nearly linear-phase response is presented using fractional derivative constraints(FDCs).In the proposed method,design problem of an IIR frlter is constructed as the minimization of phase error between the desired and designed phase response of an allpass filter(APF)such that the designed lowpass filter(LPF)or highpass frlter(HPF)yields less passband(ep),and stopband errors(es)with optimal stopband attenuation(As).In order to have accurate passband(pb)response,FDCs are imposed on appropriate reference frequency,where the optimality of these FDCs are ensured by using a new greedy based sorting mechanism.The simulated results reflect the efficiency of the proposed method in term of improved passband response along with better transition width.However,small reduction in^is observed within the allowable limit,when compared to noin-fractional design approach,but the designed filter remains immune to wordlength(WL)effect.     

Marquardt optimization method to design two-channel quadrature mirror filter banks

This paper proposes an efficient method for the design of two-channel, quadrature mirror filter (QMF) bank. The design problem is formulated to minimize an objective function, which is a linear combination of pass-band error and stop-band residual energy of the low-pass analysis filter of the filter bank, and the square error of the overall transfer function of the QMF bank at the quadrature frequency. A new algorithm has been developed to minimize the objective function by optimizing the filter tap weights by using Marquardt optimization method. Simulation results of the algorithm show that the performance of the proposed method is better than that of the already existing methods.     

Design of two-channel quadrature mirror filter bank using particle swarm optimization

In this paper, a particle swarm optimization (PSO) is used to design the quadrature mirror filter (QMF) banks with linear phase in frequency domain. A unique PSO is developed to optimize filter bank coefficients to match the ideal system response. The three main attributes used in assessing the performance of filter are reconstruction error, mean square error in pass band and mean square error in stop band. The proposed PSO based method produces almost the same result as that of the existing methods. As compared to the existing methods this method is very simple to implement for the QMF bank optimization. To implement the proposed PSO algorithm, a Matlab program is developed and three examples have been presented to illustrate the performance of the proposed method.     

High order stable infinite impulse response filter design using cuckoo search algorithm

In this paper, an efficient technique for optimal design of digital infinite impulse response (IIR) filter with minimum passband error (e _p ), minimum stopband error (e _s ), high stopband attenuation (A _s ), and also free from limit cycle effect is proposed using cuckoo search (CS) algorithm. In the proposed method, error function, which is multi-model and non-differentiable in the heuristic surface, is constructed as the mean squared difference between the designed and desired response in frequency domain, and is optimized using CS algorithm. Computational efficiency of the proposed technique for exploration in search space is examined, and during exploration, stability of filter is maintained by considering lattice representation of the denominator polynomials, which requires less computational complexity as well as it improves the exploration ability in search space for designing higher filter taps. A comparative study of the proposed method with other algorithms is made, and the obtained results show that 90% reduction in errors is achieved using the proposed method. However, computational complexity in term of CPU time is increased as compared to other existing algorithms.     

近似完全重构DFT调制滤波器组的设计

提出了一种新的近似完全重构（NPR）离散傅立叶变换（DFT）调制滤波器组的原型滤波器设计方法。其优化的目标函数由滤波器组的输出混叠、输出失真及原型滤波器的阻带能量所导出。在此设计方法中,利用DFT调制滤波器组的特殊结构合理简化了滤波器组的输出混叠,输出失真。原型滤波器的设计最终被转化为一个简单的非线性优化问题。与目前的DFT调制滤波器组的设计方法相比,该方法提供了相当大的灵活性同时具有简单的优化描述。仿真结果证实了所提出的设计方法的有效性。     

Coupled‐line band‐pass filter with T‐shaped structure for high frequency selectivity and stopband rejection

A coupled‐line band‐pass filter (BPF) with T‐shaped stub structure is presented. Five transmission poles within the passband and eight deep transmission zeros (TZs) from 0 to 2f₀ (f₀ denotes filter's center frequency) are realized through input impedance calculations. With the simple T‐shaped structure, the positions of six TZs can be appropriately adjusted to achieve high frequency selectivity and stopband rejection. For demonstration, a BPF prototype centered at 2.05 GHz is designed and fabricated, whose measured rejection levels are of over 45.5 dB at lower stopband and better than 19.5 dB at upper stopband. The simulation and measurement results are in good agreement, which validates the design idea.     

Alternating Analysis and Synthesis Filters: A New Pseudo-QMF Bank

Cruz-Roldán, F., Amo-López, P., Martín-Martín, P., and López-Ferreras, F., Alternating Analysis and Synthesis Filters: A New Pseudo-QMF Bank, Digital Signal Processing11 (2001) 329–345The process of designing a prototype filter for a pseudo quadrature mirror filter (QMF) cosine-modulated bank can require the optimization of a highly nonlinear cost function to obtain its coefficients or the calculation of a spectral factor of a valid 2Mth band filter. This article presents a new method for designing pseudo-QMF banks in which none of the aforementioned procedures are required. To obtain the coefficients of the prototype filter we can use any technique which enables us to design linear-phase Type I or Type II FIR filters. The result is a system in which amplitude distortion is very low, there is no phase distortion at all, and aliasing is slightly higher than the stopband attenuation of the prototype filter obtained. Several examples are included.     

An efficient iterative method for nearly perfect reconstruction non-uniform filter bank

In this paper, a computationally efficient iterative algorithm is presented for the design of multi-channel nearly perfect reconstruction nonuniform filter bank using the modified window functions such as Kaiser, Cosh and Exponential windows with exploiting a new perfect reconstruction condition of nonuniform filter banks instead of using complex objective functions. The cutoff frequency is optimized using linear optimization technique such that the magnitude response of a prototype filter at quadrature frequency is approximately equal to 0.707. The simulation results illustrate significant reduction in amplitude distortion, number of iteration and computation time as compared to earlier existing techniques. The proposed algorithm is simple, easy to implement, and linear in nature. When exploited for subband coding of electrocardiogram (ECG) signals, the proposed method yields good fidelity performance measuring parameters.     

A multi‐stub loaded compact UWB BPF with a broad notch band and extended stopband characteristics

A compact ultrawideband (UWB) bandpass filter (BPF) employing the principle of multiple mode resonance characteristics to create UWB passband with high selectivity and simultaneously having extensive stopband characteristic is presented. Utilizing five stubs attached along with the asymmetric trisection stepped impedance resonator (ATSSIR), the proposed resonator enables seven transmission poles inside the passband. As an additional attributes the projected filter triggers one transmission zero at 5.0 GHz which helps to mitigate WLAN signal interference. No additional circuitry is used to generate a notch band. The proposed prototype of UWB BPF is fabricated and estimated. Simulated and estimated results are in great understanding. The prospective filter displays a deliberate passband from 2.9 to 11.02 GHz. The filter unveils deceptive free wide upper stop band attributes till 25 GHz with least attenuation of 10 dB all through the stop band.     

线性相位NPR DFT滤波器组设计

提出了一种具有不同分析和综合原型滤波器的线性相位过采样NPR DFT调制滤波器组的设计方法。根据滤波器组在子带混叠、系统输出混叠、系统失真三方面的要求,推导并给出了相应的设计算法。不同的分析、综合原型滤波器的使用增加了设计自由度,可以有效改善滤波器组的整体性能。另外,由于考虑了线性相位约束,滤波器组的通带平坦性约束变得更为简单,简化了设计算法。     

Design and fabrication of microstrip lowpass filter using asymmetric hairpin resonator

In this letter, a compact microstrip lowpass filter (LPF) is designed using serial connecting of two modified asymmetric hairpin resonators. The proposed design is consists of four open‐circuited stubs that are used to suppress spurious harmonics in the stopband. The proposed filter has wide‐stop band with attenuation level better than ?28 dB from 2.16 up to 26.1 GHz and sharp roll‐off. The proposed LPF has ?3 dB cutoff frequency equal to 2.11 GHz, wide stopband width around 12th harmonic suppression and insertion loss less than 0.1 dB at about 85% of the passband. The excellent agreement is observed between the simulated results and measured values of the fabricated LPF.     

Design of coplanar waveguide elliptic low pass filters

This article proposes three design topologies of coplanar waveguide elliptic low pass filters. The design procedure is simple and explained in detail for the first topology. Numerical results are provided using the commercially available simulation softwares IE3D and HFSS to show the validity of the design with very good agreement. The proposed filters yield less than 0.1 dB attenuation in the passband (0–2 GHz), with a controllable slope of the transition between passband and stopband. The width of the rejection band is increased by simple filter cascading resulting in a passband to stopband ratio of up to 1:6. © 2009 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2009.     

Novel configuration of ultra‐wide band uni‐planar configuration of complementary split ring resonator composite right/left‐handed based band pass filter with sharp roll off and good stopband attenuation

In this paper, a compact novel simple design of ultra‐wide bandpass filter with high out of band attenuation is presented. The filter configuration is based on combining an ultra‐wide band composite right/left‐handed (CRLH) band pass filter (BPF) with simple uni‐planar configuration of complementary split ring resonator (UP‐CSRR). By integrating two UP‐CSRR cells, the ultra‐wideband CRLH filter roll‐off and wide stopband attenuation are enhanced. The filter has 3 dB cutoff frequencies at 3.1 GHz and 10.6 GHz with insertion loss equals 0.7 dB in average and minimum and maximum values of 0.48 dB and 1.05 dB, respectively over the filter passband. Within the passband. The transition band attenuation from 3 dB to 20 dB is achieved within the frequency band 1.9 GHz to 3.1 GHz (48%) at lower cutoff and the frequency band 10.6 GHz to 11.4 GHz (7%) at upper stopband. Moreover, the filter has a wide stopband attenuation >20 dB in frequencies 11 GHz to 13.6 GHz (21%) and ends with 3 dB cutoff frequency at 14.8 GHz. Furthermore, the designed filter size is very compact (23 × 12 mm²) whose length is only about 0.17 λ_g at 6.85 GHz. The filter performance is examined using circuit modeling, full‐wave simulations, and experimental measurements with good matching between all of them.     

A compact realization of composite low‐pass filter for monolithic microwave integrated circuit applications

A compact realization of composite low‐pass filter is presented in this article. The filter is realized using on‐chip spiral inductors and metal–insulator–metal capacitors and features an attenuation pole near the cutoff frequency leading to a sharper attenuation response. As well, it offers good matching properties in the passband. Space‐mapping‐based algorithm is used in the design/optimization of spiral inductors toward achieving high quality factors at the filter cutoff frequency. The realization of the proposed filter is compact in size, suitable for monolithic microwave integrated circuit applications, and exhibit broad upper stopband frequency characteristics. © 2011 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2012.     

Compact lowpass filter with sharp roll-off and wide stopband using dual-stepped impedance resonator

A lowpass filter unit with sharp roll-off and wide stopband using dual-stepped impedance resonator （DSIR） is presented. The lowpass filter unit is composed of DSIR, open circuited stubs, and high-impedance transmission lines. DSIR mainly dominates the passband and stopband width while open stubs are used to enhance the suppression level with one transmission zero. Three transmission zeros are introduced to stophand and one closed to passband edge. Thus, a very sharp transition can be achieved. A compact lowpass filter with sharp roll-off rate of 201 dB/octave, wide stopband of 5.9fc, and high suppression level of 30 dB was obtained when two asymmetric units were cascaded.