基于高温超导材料的折叠交指低通滤波器设计

传统的椭圆函数低通滤波器基于半集总参数的高低阻抗线实现椭圆函数LC网络,其尺寸较大,特别是对于低截止频率的低通滤波器,难于在高温超导晶圆片有限尺寸内实现与带通滤波器的集成。提出了一种基于高温超导材料的折叠交指低通滤波器设计,其折叠交指谐振器不仅自身具有椭圆函数低通特性,能够有效抑制高次寄生通带,而且通过折叠与交指结构实现了低通滤波器的小型化,便于与带通滤波器的集成。通过电磁(EM)仿真验证了该设计的可行性与有效性。该结构非常适用于小尺寸、低频低通滤波器的设计。     

基于电流传送器的椭圆函数滤波器设计

本文采用电流传送器CCII+/-的模块单元设计实现高阶椭圆函数滤波器,实现方法为对所设计的无源高阶滤波器用信号图（SFG）进行模块化综合,用电流传送器CCII+/-实现SFG中的各个模块单元。所实现的有源CCII+/-滤波器中所有电阻,电容都接地,适于全集成。     

Direct derivation and refinement of generalized Cohn-Matthaei formulas for resonator coupling coefficients in a microwave filter

Generalized formulas for direct synthesis of bandpass filters are presented. The formulas are derived on the basis of a lowpass prototype filter formed from lumped reactive elements and on the definitions of the coupling coefficient and the quality factor of the filter resonators. In deriving the formulas, neither the equivalent circuits with impedance inverters nor linear approximations of the frequency dependences of the immitances of reactive elements are used. The frequency characteristics of a simple filter that is formed by a cascade connection of alternating low-impedance and high-impedance half-wavelength sections and is synthesized using both the approximate and refined formulas are compared.     

The utility of the composite cascode in analog CMOS design

This work demonstrates the utility of the composite cascode stage by considering its use (1) as a high-gain amplifying stage; (2) as a high-impedance load for an amplifying stage; and (3) as a low-impedance, high-frequency summing circuit. A simulation of the summing circuit using 0.18?µm channel lengths leads to a rise time of less than 30?ps and good linearity. When used as a high-gain amplifier, both devices of the active cascode stage must be biased into the active region. In the summing circuit, one device is biased into the triode region whereas the second device must operate in the active region. Guidelines for achieving proper bias with a single bias source are provided in this work.     

New realization of inductances for switched-capacitor filters using voltage inverter switches

This paper describes a new design method of inductance simulation for switched-capacitor (SC) filters based on the VIS-SC concept. The resulting circuits have not only the excellent sensitivity behavior of VIS-SC filters, but also the low sensitivity to the main parasitics occuring in the MOS integrated circuit, i.e., the parasitic capacitances between the bottom plates of the implemented capacitors and substrate. As examples, a sixth-order band-pass and a sixth-order band-stop elliptic filter transformed from a third-order low-pass are given. Experimental results agree very well with theory. A brief analysis is given of certain parasitic effects in band-stop filters at the Nyquist frequency.     

Field programmable analog arrays for implementation of generalized nth‐order operational transconductance amplifier‐C elliptic filters

This study presents a new architecture for a field programmable analog array (FPAA) for use in low‐frequency applications, and a generalized circuit realization method for the implementation of nth‐order elliptic filters. The proposed designs of both the FPAA and elliptic filters are based on the operational transconductance amplifier (OTA) used in implementing OTA‐C filters for biopotential signal processing. The proposed FPAA architecture has a flexible, expandable structure with direct connections between configurable analog blocks (CABs) that eliminates the use of switches. The generalized elliptic filter circuit realization provides a simplified, direct synthetic method for an OTA‐C symmetric balanced structure for even/odd‐nth‐order low‐pass filters (LPFs) and notch filters with minimum number of components, using grounded capacitors. The filters are mapped on the FPAA, and both architectures are validated with simulations in LTspice using 90‐nm complementary metal‐oxide semiconductor (CMOS) technology. Both proposed FPAA and filters generalized synthetic method achieve simple, flexible, low‐power designs for implementation of biopotential signal processing systems.     

半集总参数环形电桥设计

本文利用集总电路模型 ,用微带高、低阻抗线实现环形电桥 ,组成 180°功分器 ,用于四线螺旋天线的激励。由于利用半集总参数设计思想 ,功分网络的尺寸减小了一半。     

Systematic Generation of Current-Mode Linear Transformation Filters Based on Multiple Output CCIIs

A transformation called current-mode linear transformation (CMLT) and its filter applications using multiple output second-generation current conveyors (MOCCIIs) are presented. The systematic method is developed to realize CMLT MOCCII-based filters efficiently. Based on the proposed design tables, we can synthesize high-order current-mode all-pole and elliptic filters with MOCCIIs, grounded resistors and capacitors. Moreover, the high-frequency elliptic filter can also be efficiently realized by adding capacitors to the relative all-pole filter, although floating capacitors are needed. Third-order Chebychev and elliptic lowpass filters are described in this paper. Experimental results that confirm the theoretical analysis are obtained. Furthermore, the proposed circuits can be extended to higher-order filters.     

Ultra-Wideband Bandpass Filter Using Multilayer Liquid-Crystal-Polymer Technology

Novel ultra-wideband (UWB) bandpass filters are proposed based on quasi-lumped-element prototypes and implemented with multilayer liquid-crystal-polymer (LCP) technology. In this study, the broadside-coupled microstrip radial stubs and high-impedance microstrip lines are adopted as quasi-lumped elements for realizing compact UWB bandpass filters. By introducing a short-circuited high-impedance microstrip line as a shunt inductor and suitably designing quasi-lumped-element capacitors, a compact six-pole bandpass filter is implemented with the Federal Communications Commission (FCC) defined UWB specifications. To further improve the selectivity and wideband performance, an eight-pole filter of this type is developed by adding two shunt short-circuited microstrip stubs, which introduce a transmission zero at the upper passband edge. The proposed filters are fabricated using multilayer LCP technology. Good agreement between simulated and measured results of these filters are observed. The measured results show that the fabricated six-pole filter has good specifications for the FCC-defined UWB system. The fabricated eight-pole filter has an ultra-wide fractional bandwidth (139%) and a good stopband rejection level, which is higher than 38.1 dB from 10.57 to 18.0 GHz. The proposed filters are attractive for UWB communications and radar systems.      

Table-based linear transformation filters using OTA-C techniques

Linear transformation (LT) active filters using operational transconductance amplifiers (OTAs) and capacitors are presented. Based on the LT, two simple and systematic design tables are given to realise OTA-C filters efficiently. Using the proposed design tables, the synthesised all-pole and elliptic filters employ minimum numbers of OTAs and only grounded capacitors. As an example, a new third-order elliptic lowpass filter is realised. Experimental results are obtained to verify the theoretical analysis     

Miniaturized thick-film RC-active filters for PCM application

This paper presents thick-film RC-active filters developed for use in pulse-code modulation (PCM) systems. Filters for PCM telephone transmission systems are required to be small in size and low cost in production, and they must have good performance. The filters presented have a twelve-lead single in-line package configuration. Dimensions are 5-mm thick, 10-mm high, and 30-mm wide. They meet the D3-Channel Bank requirements. The transmitting filter is a seventh-order bandpass filter (BPF). The receiving filter is a fifth-order low-pass filter (LPF) with an input RC stage which acts as a lossy sample and hold circuit. To achieve miniaturization, thick-film resistors are printed on one side of alumina substrate. On the other side, one chip of quad op-amps and monolithic ceramic-chip capacitors are assembled. Considering economical production, these filters are designed with the following features: 1) only one type of equal-valued capacitors is used; 2) to get good yields, a multiple-feedback configuration having low sensitivity to circuit elements is adopted; 3) a fast deterministic trimming method is used with computer-controlled laser-trim equipment.     

Suppression of Second and Third Harmonics Using $lambda/$4 Low-Impedance Substrate IntegratedWaveguide Bias Line in Power Amplifier

In this letter, a low-impedance substrate integrated waveguide (SIW) bias line is proposed to suppress second and third harmonics in power amplifier. Such a bias line consists of a 4 low-impedance microstrip line and a shorted SIW that can operate as a radio frequency block and suppress any harmonic signals from entering the dc source. Since the frequency of the second harmonic components is lower than the inherent cutoff frequency of the SIW, second harmonic components are blocked. At the same time, third harmonic components are shorted by the shorted SIW. Measured results show that second and third harmonic components can be reduced by 25 dB and 13 dB, respectively, compared to the outcomes using conventional 4 high-impedance microstrip bias line. Also, both 1 dB compression point and power added efficiency are improved slightly.     

Realization of current-mode high-order filters employing multiple output OTAs

Current-mode linear transformation (CMLT) high-order filters with minimum number of multiple output operational transconductance amplifiers (MOOTAs) are presented. Based on proposed design methods, we can synthesize current-mode high-order all-pole filters with minimum number of MOOTAs and all grounded capacitors efficiently. Moreover, high-frequency canonical CMLT elliptic filters with minimum number of MOOTAs and floating capacitors are also presented. Our proposed filters have the following merits: simplified design procedures, minimum number of active elements and simple design equations. Two design examples are demonstrated in this paper. Experimental results that confirm the theoretical analysis are provided.     

Micromachined filters on synthesized substrates

Effective high-frequency spectrum usage requires high-performance filters to have a sharp cutoff frequency and high stopband attenuation. Stepped-impedance low-pass designs achieve this function best with large ratios of high-to-low-impedance values. In high-index materials, such as Si (11.7) and GaAs (12.9), however these high-to-low-impedance ratios are around five, thereby significantly limiting optimum filter performance. This paper characterizes the use of Si micromachining for the development of synthesized substrates, which, when utilized appropriately, can further reduce the low-impedance value or increase the high-impedance value. Both designs have demonstrated high-to-low-impedance ratios that are 1.5-2 times larger than conventional techniques     

Efficient implementation of tunable ladder filters using multi-output current controlled conveyors

A methodology to realize continuous-time current-mode tunable ladder filters of any order has been presented. This proposed technique individually simulates signal flow graph (SFG) of each branch element from passive filter prototype using only multi-output second generation current controlled conveyors (MCCCIIs) and grounded capacitors. This leads to simple structure, ease of design and suitability for IC fabrication. A third-order Butterworth low-pass filter, a third-order elliptic low-pass filter and a sixth-order Chebyshev band-pass filter are employed to demonstrate the proposed realization scheme. These simulated filters retain minimum requirement of passive and active elements and provide the filter corner frequency tunability. Moreover, the method allows an implementation of the elliptic filters by simply adding floating capacitors to all-pole filter structures.     

Input filter design for power factor correction circuits

The issues involved in the design of power factor correction circuit input filters are significantly different from those involved in the design of input filters for DC-DC power converters. In many cases, the EMI and power factor requirements are impossible to meet using the existing filtering technology. This paper proposes the use of high-order elliptic filters to achieve the required EMI attenuation and power factor. The new input filter technology provides a significant filter size reduction over the standard filter designs, minimizes the filter-power converter interaction, and maintains a good converter power factor. New active and passive filter damping methods that guarantee optimal filter pole damping, while virtually eliminating damping resistor power dissipation, are proposed. The filter design procedure that makes possible a simple and fast design of filters with an arbitrary number of stages is also presented     

Current-mode elliptic filter design based on symmetrical current switching

This paper describes a current-mode elliptic filter structure based on dual-output OTAs and grounded capacitors. The filter is capable of producing both lowpass and highpass notch responses without changing the filter structure. This is achieved using a symmetrical current switching technique based on two switches controlled with a 2-bit digital word. The proposed filter structure forms a basic second-order building block in the design of high-order elliptic filters with tuneable frequency response. To confirm the theoretical analysis, simulated and measured results of fourth-order elliptic lowpass and highpass filters with tuneable bandwidth in the range of 0.65MHz to 1.3MHz are included. Finally, detailed analysis of the OTAs non-ideal parameters on the filter performance is presented and an example is given.     

Current-Mode Linear Transformation Filters Using Current Mirrors

Novel building blocks for designing high-order current-mode filters by employing current mirrors as the elementary active elements are introduced in this paper. As a design example, a fifth-order elliptic current-mode filter is designed using only grounded capacitors. Simulation results using transistor parameters of a typical CMOS 0.35- technology are in a good agreement with the theoretically expected. A comparison with the corresponding current mirror based filter topologies realized using the leapfrog and the wave techniques has been also performed. For this purpose, new leapfrog and wave filter topologies are introduced. Comparison results confirm the benefits offered by the proposed filter configurations.     

New compact low-pass filter (LPF) using cascaded square open loop resonator

This article introduces a new design technique of low-pass filter using cascaded square open loop resonator (SOLR) for the multi-wireless communication system. In the design procedure, a half-wavelength SOLR is realized with 6 GHz to meet the desired LPF cut off frequency. As the resonator is fed by a direct connection of 50-ohm input/output ports, the structure is directly transferred into a second-order low-pass filter with elliptic behavior. An equivalent circuit is extracted and its lumped elements are computed to support the proposed second-order LPF. Based on the equivalent circuit, highly selective third and fifth-order LPFs with wide rejection band are developed. To achieve this development several SOLR are cascaded by a direct connection. The designed filters are implemented on a grounded substrate which has relative permittivity of 6.15 and thickness of 0.508 mm. To verify the design concept, a third-order LPF using two cascaded SOLRs is designed, simulated, fabricated and measured. The filter responses obtained from theory, simulation, and measurement show good agreement. The filter has very small circuit area about 31 mm² excluding the input/output feeding ports.     

Synthesis of Distributed Elliptic-Function Filters from Lumped-Constant Prototypes

A synthesis procedure for distributed elliptic-function filters utilizing published tables of lumped-constant elliptic-function filters has been devised. It is dependent upon the application of a new generalized transformation for distributed networks. The filters often require the realization of distributed Brune sections, and several novel practical realizations are given both for general and degenerate Brune (i.e., Foster) sections. Examples are given of elliptic function stop band and pass band filters having both wide and narrow bandwidths, and experimental results show good agreement with theory.