Design of Bessel low-pass filter using DGS for RF/microwave applications

A synthesis method to design a defected ground structures (DGS)-based Bessel low-pass filter (LPF) using a triangular and an open-square (OS)-type DGS is reported. For the five-pole Bessel LPF at f_c = 2.5 GHz, we get 10.6 dB/GHz selectivity using the triangular DGS; while the OS-type DGS provides 39 dB/GHz selectivity. For these two filters, the 10 dB impedance matching BW is 76% and 84%, respectively. It is a much wider BW that is obtained for a lumped element Bessel LPF. The maximum group delay (GD) variation within the pass band is 25pS and 28pS, respectively. The 20 dB rejection BW can be increased from 5.8 GHz to 18.8 GHz with increase in the order of filter from 5 to 11. We have also presented the design of a compact five-pole DGS-based elliptic filter with selectivity 38.2 dB/GHz and 17.8 dB return loss. Results on the DGS-based elliptic filter, Butterworth and Chebyshev filters are also presented. The experimental results are compared against the recently reported LPFs. Our reported filters perform better with respect to selectivity and group delay variation. The flatter GD and high selectivity, along with a wide 10 dB impedance matching BW, make the DGS Bessel filter a candidate for high-speed data communication, front end of a wideband communication system and efficiency improvement of a power amplifier.     

一种新型一维周期DGS单元结构特性研究

该文设计了一种新型一维周期地面缺陷(Defected Ground Structure, DGS)单元结构,该DGS单元结构提高了等效电感。增加的等效电感可以容易控制DGS平面电路的截止频率特性。设计的周期DGS单元结构有非常好的截止和带阻特性。为了显示改进的等效电感,该文设计了3个周期相同而单元尺寸不同的DGS电路。DGS电路的测试结果显示截止和带阻的中心频率特性由该DGS单元结构的物理尺寸决定。     

Design of compact bandpass filter for WiMAX and UWB application using asymmetric SIRs and DGS

This paper considers a novel compact tri-band microstrip bandpass filter, the design of which employs asymmetric SIRs and DGS for achieving the characteristics of low insertion loss, high selectivity, wider range of bandwidth, and low group delay for 2.5/3.4 GHz (WiMAX) and 4.14–5.32 GHz (UWB) bands. The novel filter design implies the intentional selection of impedance ratio R and the length of the microstrip of asymmetric SIRs; in addition, DGS is used to improve the coupling strength of the last band. The scattering parameters of the three passbands have the following values: insertion losses S₂₁ are–0.26/–0.07/–0.05 dB, and return losses S₁₁ are–11.29/–19.25/–22.64 dB, respectively. The response of the filter was simulated using Ansoft HFSS simulator.     

低辐射DGS 及其串扰分析

在传统哑铃形缺陷接地结构(DGS)的基础上,设计出一种新型低辐射DGS。该结构既具有传统DGS的优良电路性能,又大大降低了由于接地面蚀刻缺陷图案而引起的无意辐射。进一步仿真分析了低辐射DGS 的串扰,结果表明低辐射DGS 近端串扰峰值电压较哑铃形DGS 下降60%,远端串扰峰值电压下降了36. 8%,证明低辐射DGS 能大大降低由于DGS 的应用对周围电路产生的影响。与接地面完整的平行微带线相比,低辐射DGS 近端串扰略大,但远端串扰在4 ~6 GHz 频段内存在阻带,当受扰线工作在远端串扰的阻带频段内,对远端串扰的抑制效果十分明显。     

一种新颖的开口环地面缺陷结构低通滤波器

提出了一种新颖的具有陡峭边带和宽阻带的小型化低通滤波器.通过把开口谐振环地面缺陷结构(Split-Ring Resonator Defected Ground Structure,SRR DGS)与阶梯阻抗梳状谐振器结合,提高了滤波器的选择特性,同时获得了宽阻带.对所提出的结构作了加工并进行了实物测量,测试结果表明:滤波器选择特性大于160 dB/GHz,在2.98 GHz到8.2 GHz范围内抑制度大于20 dB,而占用面积仅为20×25 mm~2.     

一种宽阻带带通滤波器的设计方法

基于非相似谐振结构具有不同杂散谐振频率特性,研究并设计了一个具有较高带外抑制特性的微带带通滤波器,提高了微波滤波器的带外抑制特性。首先简要介绍了利用非相似谐振结构抑制寄生通带的原理。尔后,利用ADS软件分别设计了两个分别采用λ4相同谐振结构和λ4非相似谐振结构的滤波器。通过对比,验证了该方法正确性,进一步说明了非相似谐振结构在设计宽阻带、高选择性微带带通滤波器的有效性。     

小型高带外抑制超宽带滤波器设计

为了提高滤波器的带外噪声抑制,并兼顾小型化,提出了一种新型超宽带滤波器设计。首先,利用分路电磁耦合结构在通带两侧实现了2个传输零点,通过调节中间金属片与螺旋缺陷地可实现对2个零点的单独调节,由此实现了高带外抑制,且有利于滤波器的小型化;然后,利用基片集成波导与周期性缺陷地结构,在进一步提高频率选择性的同时,实现了较好的阻带性能;最后,设计并加工了一款工作频率为8.1 GHz、带宽为67%的滤波器。结果表明,仿真与测试结果吻合良好,证明了该设计方法的可靠性。     

Reduction of mutual coupling and cross-polarization of a MIMO/diversity antenna using a string of H-shaped DGS

In this article, a simple string of H-shaped defected ground structure (DGS) is used to reduce the mutual coupling and cross-polarization of a MIMO antenna. A MIMO antenna has been designed using two identical square patches to operate at the frequency of 2.4 GHz. The proposed DGS decreases the direct coupling path among the closely spaced (edge to edge gap 0.038 λ₀) patches and thereby reduces the mutual coupling and cross-polarization by 46 dB and 11 dB respectively. To study the amount of mutual coupling is decoupled; a new term namely, coupling to decoupling ratio (CDR) has been defined. A mathematical model is developed using multiple polynomial regression analysis techniques to observe the dependency of CDR as a function of frequency and inter-element spacing. Also, an equivalent circuit of the DGS is constructed and validated. Diversity performance of this MIMO antenna is presented through Envelope Correlation Coefficient (ECC) and Mean Effective Gain (MEG) ratio and well acceptable values of 0.0002 and 0.03 dB are obtained respectively. A prototype is fabricated and measured. The experimental results show good agreement with that of the simulated results. Maximum peak gain of 2dBi and radiation efficiency of 74% also proves the practicality of this design.     

一种按照指数函数相对振幅分布的新型周期DGS微带线设计

设计了一种新型一维周期接地缺陷结构(DGS)微带线。与传统的周期均匀DGS单元微带线不同的是,这种改进的周期DGS平面电路是一种补偿的微带线,每个DGS单元尺寸是不同的,尺寸按照指数函数e1/n(n为正整数)的相对振幅变化。本文设计了一个均匀周期DGS平面电路和两个改进的周期DGS平面电路,测量结果显示改进的周期DGS平面电路能够更好地抑制波纹和增大带阻带宽。     

Wide-stopband microstrip bandpass filters using dissimilar quarter-wavelength stepped-impedance resonators

Wide-stopband and compact microstrip bandpass filters (BPFs) are proposed using various dissimilar quarter-wavelength (/spl lambda//4) stepped-impedance resonators (SIRs) for multiple spurious suppression. The use of /spl lambda//4 SIRs is essential in widening the filter stopband and reducing the circuit size. By properly arranging the individual /spl lambda//4 SIR, which has the same fundamental resonance frequency f/sub 0/, but has different spurious (harmonic) resonance frequencies, and also carefully misaligning the maximum current density nodes, several higher order spurious resonances may be suppressed so that a BPF with wide stopband may be realized. In this study, the basic concept of multiple spurious suppression is demonstrated by thoroughly investigating the spurious characteristics of the fourth-order interdigital BPFs, which consist of two different types of /spl lambda//4 SIRs. To widen the rejection bandwidth, the fourth-order coupled-resonator BPFs based on three and four different types of /spl lambda//4 SIRs are implemented and carefully examined. Specifically, a very wide-stopband microstrip BPF composed of four dissimilar /spl lambda//4 SIRs is realized and its stopband is extended even up to 11.4f/sub 0/ with a rejection level better than 27.5 dB.     

Compact triple-passband bandpass filter based on new modified stepped impedance resonators

This study proposed a triple-passband bandpass filter with compact size, low loss and high passband selectivity. The filter includes two coupled stepped impedance resonators (SIRs) and two embedded stub-loaded stepped impedance resonators (SL-SIRs), connected with coupling scheme at the symmetric plane of the filter. The filter is designed to have triple-passband at 2.4, 3.5 and 5.2 GHz for worldwide interoperability for microwave access (WiMAX) applications. By properly tuning the impedance ratio and physical length ratio of the SL-SIRs, the three passbands can be easily determined, at the same time, achieving the high passband selectivity and wide stopband. Besides, the transmission zeros near passband edges of each passband are generated by the proposed filter with cross-coupling structure. The measured results are in good agreement with the full-wave electromagnetic (EM) simulation results.     

Compact microstrip lowpass filter with wide stopband and sharp roll-off using tapered resonator

In this article, a novel microstrip lowpass filter (LPF) with specifications such as sharp cut-off, wide stopband, low insertion loss and high return loss using tapered resonator is presented. The LPF has cut-off frequency of 1.11 GHz, where unwanted harmonics are suppressed by novel tapered cells. The bandwidth is enhanced, and the size is reduced as compared to the conventional tapered filter. The transition band is approximately 0.29 GHz from 1.11 to 1.4 GHz with corresponding attenuation levels of –3 and –20 dB, respectively. The stopband with greater than –20 dB rejection is from 1.4 to 8.9 GHz, insertion loss in the passband is less than 0.1 dB, return loss is less than –18 dB and the overall size of the filter is 0.12 × 0.073 λ_g. The proposed filter is fabricated and measured. The simulation and measurement results are in good agreement. This LPF is designed for microwave communication applications, especially wireless video transmitters.     

一种改进的一维周期DGS微带线

设计了一种新型一维周期缺陷接地结构（Defected Ground Structure，DGS）微带线。与周期均匀圆形缺陷的DGS不同的是，改进的周期DGS是一种补偿的微带线，圆形缺陷的尺寸是不均匀的，尺寸按照指数函数e^1/n（n为正整数）的相对振幅分布。文中设计了一个均匀周期DGS电路和两个改进的周期DGS电路，测量结果显示改进的周期DGS电路能够更好的抑制波纹和增大带阻带宽。     

基于H型缺陷地结构的超宽带带通滤波器设计

微波频段的宽带滤波器一般具有通带插入损耗大,带外抑制性差等问题,为了解决这个问题,采用具有慢波效应的缺陷地结构(DGS)和缺陷微带结构(DMS),设计了一种新型微波频段的超宽带滤波器。分别利用电磁仿真软件HFSS和平面印制板技术对其进行建模仿真和实物加工。实测与仿真结果良好吻合,带内插入损耗优于1.64dB,回波损耗优于13.93dB,通带范围在2.75~8.3GHz,实现相对带宽100.45%,高低阻带均抑制在-10dB以下,且该滤波器结构紧凑,体积小。     

Miniaturized microstrip lowpass filter with wide stopband using double equilateral U-shaped defected ground structure

A compact double equilateral U-shaped defected ground structure (DGS) unit is proposed. In contrast to a single finite attenuation pole characteristic offered by the conventional dumbbell DGS, the proposed DGS unit provides dual finite attenuation poles that can be independently controlled by the DGS lengths. A 2.4-GHz microstrip lowpass filter using five cascaded double U-shaped DGS units is designed and compared with conventional DGS lowpass filters. This low pass filter achieves a wide stopband with overall 30-dB attenuation up-to10 GHz and more than 42% size diminution.     

小型化多层带线谐振腔缺陷地结构LTCC宽带带通滤波器

利用多层宽边耦合带状线谐振结构实现小型化LTCC(LowTemperature Co-fired Ceramic)宽带滤波器。采用了两层、三层耦合带线谐振结构,利用这两种谐振结构可以有效减小滤波器的尺寸。利用四个谐振腔结构,实现较宽的频带和较强的选择特性;输出、输入引入电感反馈产生两个传输零点,利用DGS(Defected Ground Struc-ture)可使滤波器在阻带和镜像频率处产生较大的衰减。设计出侧面印刷互连和侧面通孔互连两种工艺结构的滤波器,利用LTCC工艺加工出侧面印刷互连的滤波器性能良好,测试性能和仿真结果基本吻合。     

An improved 1D periodic defected ground structure for microstrip line

A novel one-dimensional (1-D) periodic defected ground structure (DGS) for microstrip line is presented in this letter. Different from the periodic DGS with uniform square-patterned defects, the improved periodic DGS has a compensated microstrip line and the dimensions of the square defects are nonuniform and varied proportionally to the relative amplitudes distribution of the exponential function e/sup 1/n/ (n denotes the positive integer). A uniform periodic DGS circuit and two improved periodic DGS circuits are designed, fabricated, and measured. Measurements show that the latter exhibit more excellent performances by suppressing ripples and enlarging stopband bandwidth.     

Compact wide stopband lowpass filter using spiral loaded tapered compact microstrip resonator cell

A new spiral loaded tapered compact microstrip resonator cell (SPLT-CMRC) is presented. The addition of spiral stubs to the CMRC creates transmission zeroes in the stopband which extended the stopband of the ?lter. The proposed resonator is used to design a compact lowpass ?lter (LPF) with wide and high rejection in stopband. The fabricated ?lter has a 3 dB cutoff frequency at 8 GHz. The insertion loss in the passband is less than 0.2 dB from DC to 7.2 GHz. The proposed ?lter has wide stopband from 9.47 to 40 GHz with attenuation level of ?20 dB. The demonstrated filter is designed and fabricated. There is a good agreement between the measured and simulated S-parameters.     

1D非周期缺陷地结构微带线

针对50?微带线提出了新型一维非周期缺陷地结构(DGS)电路,不同于周期DGS,新型的DGS单元晶格是非周期的。设计、制造、测试了两个改进的缺陷地结构电路,测试结果表明该新型DGS可以产生通带和较宽的阻带。     

A new method for designing multiplierless two-channel filterbank using shifted-Chebyshev polynomials

This paper presents an efficient design method for a digital multiplierless two-channel filterbank using the shifted-Chebyshev polynomials and common sub-expression elimination (CSE) algorithm for reducing hardware requirements such as adders and multipliers. For designing a two-channel filterbank, the design problem is constructed as minimization of integral mean square error between the desired and designed response of a prototype filter in the passband and stopband. For controlling the performance in passband and stopband, two parameters (K_P, and K_S) are used, whose optimum values are determined by swam optimization techniques such as differential evolution algorithm, artificial bee colony optimization, particle swarm optimizations, cuckoo search algorithm and hybrid method using a fitness function, constructed by perfect reconstruction condition of a filterbank. The number of polynomials used for approximation depends upon the order of a prototype filter. A new hybrid CSE is proposed for further reduction of hardware requirement. A comparative study of various CSE techniques such as horizontal, vertical and proposed hybrid CSE is also made. Numerical examples illustrate the effectiveness of the proposed algorithm in the reduction of adders with comparisons accomplished using existing methods. It has been found that almost 43% adder gain can be achieved when a filter is designed with N = 32 and wordlength (WL) as 12 using proposed methodology.