Low-noise and low-sensitivity filters using current-mode coupled biquads

In this paper, it is shown that by adding coupling to biquad pairs to obtain a fourth-order band-pass filter, the output thermal noise is reduced. It is shown analytically that minimum output thermal noise is obtained when the biquads are identical and the negative-feedback factor used for coupling is the same as for the minimum sensitivity to component tolerances and ambient changes. Furthermore, by optimizing the coupled biquads for maximum dynamic range, the output noise is further decreased.     

Multiple-critical-pole coupled active filters

In this paper realizations of low sensitivity narrow BP active filters implementing multiple-critical-pole (MCP) approximation methods and coupled filter structures are studied. In the first part of the paper, a synthesis procedure particularly developed for the realization of MCP transfer functions is described. According to that procedure the portion of the MCP transfer function containing multiple poles is realized as a follow-the-leader feedback (FLF) network, and the remaining part as a cascade. It is shown that the lower sensitivities of MCP functions in comparison with standard approximating functions (Butterworth, Chebyshev, etc.) can be further decreased by applying the FLF configuration instead of the cascade. the synthesis procedure is straightforward and in some cases it can be performed using identical second-order BP blocks. the final circuit sensitivities can be optimized according to given filter specifications and a user selected optimization criterion. In the second part of the paper, the MCP transfer functions are combined with the cascaded biquarts (CBQ), the shifted companion form (SCF), and the leap-frog (LF) structures, and sensitivity analysis is performed. It is shown that applications of the above mentioned structures can improve the filter sensitivites in a way similar to that of the given FLF configuration.     

新型开环耦合谐振滤波器的设计与应用

为了满足日新月异的无线通信对小型化带通滤波器的要求,针对传统类型滤波器存在线性度、矩形系数、插入损耗、体积等方面的问题,笔者介绍了一种通过在微带开环谐振滤波器中引入交叉耦合,产生一对传输极点,从而提高滤波器选择性的滤波器设计方法,并讨论了这种滤波器的综合方法和实现流程。实际设计了一个六阶开环谐振滤波器,并给出了全波仿真结果。分析和仿真都表明这种滤波器具有体积紧凑、选择性高的优点。     

Poles and zeros of bandpass filters for high-performance sigma-delta modulators

High-performance bandpass sigma-delta modulators find applications in digital mobile radio for accurate analogue-to-digital conversion in receivers. An approach based on the positioning of the poles and zeros is proposed for the digital design of the high-order loop filters which are required. Inverse notch filter sections are cascaded in a first step and then poles and zeros are moved to meet the performance objectives and achieve system stability. A distinct feature of the analysis and design technique presented is that it takes stability into account explicitly. Examples illustrate the practicality of the method as well as the level of performance which can be achieved in theory. the integrated circuit realization still has to be investigated to confirm the potential of the proposed design approach.     

A comparative study of multiple amplifier active RC biquadratic sections

Biquadratic sections play an important role in the design of high order active filters. This paper compares a number of popular multiple amplifier active RC biquads on the basis of their sensitivities as well as ω₀ and Q enhancement effects due to finite amplifier gain–bandwidth products (GB). For sensitivity comparison, statistical sensitivity measures, which take into account the tolerances of various passive and active elements, are used. Simple expressions for gain, phase and transfer function sensitivities are derived for the case of uncorrelated element variations. Graphic illustrations of the effects of increasing ω₀ and Q on the sensitivity measures are presented. In addition, root-loci, which show the effects of GB on the network poles are included. To further facilitate the comparison, graphs demonstrating changes in ω₀ and Q due to GB are also presented.     

一种新型微带开环滤波器的设计

对于现代移动通信设备对微波滤波器的小型化、高带外抑制的要求,提出1种基于开环谐振子的微带带通滤波器.通过一定数目的开环谐振子,产生1对传输极点,提高滤波器的带外抑制,讨论了这种滤波器的设计流程,包含了相应的公式以及精确的计算.实际设计了1个八阶开环滤波器,中心频率为1 123 MHz,相对带宽为9.534%,带外50 ...     

Ladder tuning‐block partitioned filters for simplified tuning

In this paper, we present a procedure for the design of low‐sensitivity, active‐RC filters that permits efficient functional tuning during the manufacturing process. Filters with finite zeros, such as elliptic (Chebyshev–Cauer) low‐pass filters are primarily considered, although the method can be applied to the design of other filters, e.g. allpole filters, as well. We show how to partition a given ladder filter into two parts. The first is a ladder filter of reduced order compared to the original; the second is a second‐ or third‐order active‐RC filter section, the ‘tuning block’, which, alone is used to tune the overall filter. The ladder, the components of which are fixed, provides most of the selectivity, while the cascaded tuning block determines the band‐edge characteristics and can be tuned relatively easily. A detailed design procedure for the filter partitioning is given. By obtaining a doubly terminated ladder filter, which is cascaded with a tuning block, both the inherent low sensitivity of the ladder and the tunability of the tuning block, are maintained. A Monte Carlo analysis of the partitioned filter demonstrates that the low sensitivity with respect to component tolerances, achievable by maintaining a doubly terminated ladder structure for the larger partitioned part of the filter, is preserved. Copyright © 2012 John Wiley & Sons, Ltd.     

级联型中压有源电力滤波器的研究与实现

中压和低压配电网的有源电力滤波器(APF)在检测方法和控制方法理论上是一致的。然而,受电力电子主电路电压和电流容量的限制,中压配电网的APF尚处于研究阶段。目前广泛研究的中压APF主电路结构形式主要有有源无源混合结构和多电平级联结构两种。在分析以上两种结构的特点基础上,采用一种带隔离变压器的级联型多电平逆变器作为APF主电路,具有结构简单,直流电压容易控制等显著特点。并将多载波调制和滞环电流矢量控制方法应用于实际实验装置,实验结果证明了结构和控制方法的可行性。     

On a family of new two-op-amp switched-capacitor biquads for high-frequency applications

This paper presents three novel biquads derived by applying the concept of so-called basic elements for switched-capacitor (SC) circuits. These biquads are without continuous feedback and comprise two op-amps. They were derived assuming a transfer function denominator of the same form as the Fleischer-Laker type E circuit. It is shown that by a simple modification of the switching arrangement, i.e. by changing the type of the basic SC element, the effect of the amplifier finite gain on the performance of SC filters can be significantly reduced. the efficiency of this approach has been established by extensive simulation studies using the dedicated symbolic analysis program SCYMBAL. Design equations and comparison with already known biquads of this type are presented. Examples are provided to demonstrate that the proposed circuits require a low total capacitance while finite-gain effects are considerably reduced.     

Generation and classification of single amplifier filters

A unified approach is presented for generating configurations for circuits containing one operational amplifier together with RC elements and capable of realizing a general second-order voltage transfer function. Systematic application of the generation procedure leads to various single amplifier biquads with the known circuits, as well as some new ones, obtained as special cases. The insight gained from the generalized approach as well as the results of a general sensitivity analysis (including the effects of the amplifier limited bandwidth) offer a method for categorizing and classifying single amplifier filters. The different filter classes are illustrated and compared with the aid of extensive design tables. General equations for the effect of the amplifier limited bandwidth are also given.     

基于部分电感模型的回路耦合干扰分析

电力电子系统中回路之间的电磁场耦合是电磁干扰主要传播方式之一，为了准确预测系统级的电磁干扰，需要对回路耦合干扰进行定量计算。基于部分单元等效电路(partial element equivalent circuit，PEEC)的部分电感理论，建立了典型电力电子系统回路耦合电磁干扰的模型，主要包括导线之间空间磁场形成的互感耦合和接地回路之间共地阻抗耦合的模型。在实验室中构建了物理对象研究平台，分别对差模电流和共模电流产生的回路耦合干扰进行了测试，实验结果与计算结果对比证明了方法的正确性。     

磁耦合谐振式无线电能传输ARM和CPLD控制研究

磁耦合谐振式无线电能传输是中距离传输技术。两个耦合电路通过电磁场传递能量,当发射回路和接收回路处于谐振状态时,谐振体之间能量交换效率最高。设计了1台谐振频率70 k Hz的实验装置,发射端以ARM和CPLD为主控芯片,接收端以ARM为主控芯片,分模块设计了控制电路,并提出了一种基于ARM的频率跟踪控制方法。实验表明,控制系统运行稳定,控制效果理想。     

两相“IHHI”形耦合电感的设计与应用

为了适应多相交错并联磁耦合变换器对耦合电感的要求,降低耦合电感对其它元器件的电磁干扰,降低电感加工难度和材料成本,提高电感效率,提出了一种适用于两相交错并联磁耦合变换器的"IHHI"形耦合电感结构。分析了其改变电感耦合度的原理,给出了相关铁芯设计的数学表达式,并通过有限元仿真和实验验证了所提"IHHI"形耦合电感结构的有效性及其磁路模型的可行性。将"IHHI"形耦合电感用于交错并联磁集成双向DC/DC变换器,具有输出电压纹波小、电感电流波形平滑、毛刺少、开关管开通和关断时的电流尖峰小、效率高等优点。     

On the restrictions of the sensitivities in single-amplifier biquadratic active filters

The paper deals with the bounds on the sensitivities of the poles and the quality factor to the gain of the amplifier in biquadratic second-order active filters. to ensure stability, the Fialkow-Gerst conditions are taken into account. It is not possible to realize biquad filters with a better gain-sensitivity product not obeying the derived conditions. the result can be applied in filter synthesis and will give the designer more freedom to dimension the filter structure and its component values.     

Complementary split rings resonators (CSRRs): Towards the miniaturization of microwave device design

In this paper, it is demonstrated that complementary split rings resonators (CSRRs), a new type of planar resonators recently introduced by some of the authors, are key elements for the miniaturization of microwave devices implemented in planar technology, such as filters and diplexers. These devices essentially consist on a host transmission medium (microstrip line) to which the CSRRs are electrically coupled, and additional microstructure in order to achieve the required device performance. From the analysis and numerical simulations of the equivalent circuit model of the basic device cell, as well as electromagnetic simulations of actual structures, it is confirmed that CSRRs are useful resonators for the synthesis of planar microwave filters where dimensions, out-of-band performance and bandwidth can be simultaneously optimized. The simultaneous fulfillment of these aspects is a relevant advantage of the proposed structures. The possibility to implement band pass filters with wide bandwidth and high performance, the small electrical size of CSRRs, as well as their potential applications in other microwave devices, make these particles of actual interest in microwave engineering.     

DFIG Oscillation Modes Causing Strong Dynamic Interactions to Degrade the Damping of Power System Low-Frequency Electromechanical Oscillations

Open-loop modal coupling is the closeness of an open-loop oscillation mode of a grid-connected DFIG to an open-loop electromechanical oscillation mode of a power system on the complex plane. When the open-loop modal coupling occurs, the dynamic interactions between the DFIG and the power system become strong and may degrade the damping of the low-frequency electromechanical oscillations (LEPOs) of the power system. In this article, analysis is carried out to explain why the open-loop modal coupling may cause the damping degradation of the LEPOs. By deriving the simplified open-loop transfer function matrices of the DFIG, existence of open-loop DFIG oscillation modes to cause the open-loop modal coupling is analytically examined. Conclusions of analytical examination are: (1) If the rotor speed is used as the input signal to the active power control outer loop of the rotor side converter (RSC) or the generic type 3 model is adopted by the reactive power control outer loop of the RSC, the DFIG may have an open-loop oscillation mode to cause the open-loop modal coupling; (2) The PLL may also contribute to an open-loop oscillation mode of the DFIG. Study cases are presented to demonstrate and evaluate the analysis and conclusions.     

一种级联逆变器的分散式滤波器结构研究

本文研究了一种级联逆变器的分散式滤波器结构。和采用集中式滤波器时相比,采用分散式滤波器的级联逆变器不仅具有相同的输出特性,还可以更好地实现级联逆变器的模块化;同时,分散式滤波器结构对开关管的断路故障有较好的容错性,提高了级联系统的可靠性。本文以采用倍频载波相移SPWM调制的四通道级联逆变器为例,对比分析了采用集中式和分散式滤波器的级联逆变器的性能,仿真和实验验证了级联逆变器采用分散式滤波器的可行性。     

Low‐noise,low‐sensitivity,active‐RC allpole filters using impedance tapering

In this paper it is shown that active‐RC filters whose sensitivity to component tolerances can be minimized by impedance tapering, will also have low output thermal noise. It is shown that impedance tapering will also reduce output thermal noise in OTA‐C filters. Copyright © 2010 John Wiley & Sons, Ltd.     

Single transistor RC-only second-order allpass filters

In this letter, all possible single transistor RC-only second-order allpass filters obtainable from a four impedance common-source topology are reported. It is shown that there are only seven such filters with only one of them being a minimum component canonical 2R-2C filter. Two of the found filters are designed and simulated in a 65-nm CMOS process.     

Advanced filter design technique based on equivalent circuits and coupling matrix segmentation

This paper presents a technique for the efficient design of bandpass waveguide microwave filters using a segmentation technique applied to an equivalent circuit. The technique is based on first developing an equivalent circuit that synthesizes the desired transfer function. Then, the different parts of the real physical structure are optimized by segmenting this equivalent circuit. The technique was originally developed for in‐line filters, and the main contribution of this paper is in the combination of this technique with the coupling matrix formalism. In this way, we adapt for the first time this design strategy to the design of complex coupling topologies, beyond the in‐line configuration. As an example, a complex sixth‐order dual‐mode filter, implemented in all‐inductive waveguide technology, is designed using the new coupling matrix segmentation technique, showing the effectiveness of the presented theory. A prototype of the filter has been manufactured, and the accuracy of the design technique is verified by measurements on the real prototype.