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.     

Modular log-domain filters realized using wave port terminators

Log-domain wave filters that simulate the passive LC ladder prototype filters are introduced in this paper. The proposed circuits are constructed from the wave equivalents of the reactive elements corresponding to those in the prototype circuit. The wave equivalent circuits are obtained by using a novel log-domain wave port terminator. The wave equivalent of a capacitor in a shunt branch was chosen as an elementary building block for creating high-order filters. The wave equivalent circuits of all other reactive elements in a shunt or in a series-branch connection can be readily obtained using the elementary building block plus some inverters. This way the derived high-order filter configurations are modular. A design example of a third-order elliptic low-pass filter is given, and the performance of the filter was verified by simulation.     

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     

一种新颖的电压模式N阶CFA低通滤波器的系统设计

提出了一种基于电流反馈放大器(CFA)的n阶电压模式多环反馈(multiple-loop feedback,简称MF)低通滤波器的系统设计方法,推导了系统的设计公式,利用该方法可导出n阶不同结构的低通滤波器,所产生的滤波器由n个CFA、n个电容、n个电阻构成。以三阶Butterworth低通滤波器为例阐述了设计过程,并用pspice进行仿真分析,设计和仿真结果表明,系统设计理论是正确的,设计方法是可行的。     

Analytical Synthesis of Current-Mode High-Order Single-Ended-Input OTA and Equal-Capacitor Elliptic Filter Structures With the Minimum Number of Components

None of the previously reported third-order and fourth-order operational transconductance amplifier and capacitor (OTA-C) elliptic filter structures use the minimum number of active and passive components. After an innovative algebraic decomposition for a complicated transfer function, i.e., a new analytical synthesis method, a current-mode odd-nth-order and a current-mode even-nth-order OTA-C elliptic filter structure having the following advantages are presented: 1) all the OTAs have single-ended inputs; 2) all the capacitors are grounded; 3) the minimum active and passive components are used. An equal-capacitance-type structure is designed taking into account the difficulty of precisely fabricating capacitances in integrated circuits. Although the above three advantages lead to the lowest total parasitics and to the most precise output response, the small deviations (such as the 3.5159% error in f_p) of the four parameters of the new third-order OTA-C elliptic filter can be drastically reduced (for example, to 0.1553% error in f_p) by only slightly tuning the four transconductances, but fixing the ratio of the given three capacitances, and without adding any other active and passive components. H-spice high-pass and low-pass simulations with 0.35-mum process are provided to demonstrate the theoretical results.     

FDCCII-based FDNR simulator topologies

In this article, three new circuits for realising frequency-dependent negative resistance (FDNR) are proposed. All proposed circuits employ a single fully differential current conveyor, grounded capacitors and resistor. Proposed circuits consist of minimum number of passive and active elements. All proposed circuits are lossless FDNR. The performance of the proposed FDNR is demonstrated on the third-order Butterworth low-pass filter. Simulation results are included to verify the theory.     

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.     

High-Input and Low-Output Impedance Voltage-Mode Universal Biquadratic Filter Using DDCCs

A new three inputs and single output voltage-mode universal biquadratic filter with high-input and low-output impedance using three plus-type differential difference current conveyors, two grounded capacitors and two grounded resistors is presented. The proposed circuit offers the following features: realization of all the standard filter functions, that is, high-pass, bandpass, low-pass, notch, and all-pass filters, no requirements for component matching conditions, the use of only grounded capacitors and resistors, high-input and low-output impedance and low active and passive sensitivities.     

SWITCHED-CURRENT FILTER DESIGN USING CASCADED SECTIONS

A new analogue sampled-data active device, named as a switched-current operationalamplifier (SIOA), is presented. The use of active circuit elements may simplify drawing the circuitdiagram significantly greatly and may permit easier analysis and synthesis of SI networks. Anumber of all pole and elliptic (second-or third-order) switched-current (SI) filters are derivedfrom the switched capacitor prototypes. These can be used as simple self-contained filters or asfilter sections in the cascaded realizations of a higher order transfer functions. To illustrate theapproach, a fifth-order low-pass filter is designed.     

Some Prominent Characteristics of the Modified Elliptic Low-Pass Function

A modified elliptic low-pass filter function with progressively diminishing ripples in both the passband and the stopband is proposed and analyzed. The modified elliptic function is realizable by the passive doubly-terminated ladder network for the order n even or odd, thus lending themselves amenable to high-quality low-sensitivity active RC or switched capacitor filters through the simulation techniques. Besides the passive ladder network realization, the modified elliptic function has improved characteristics both in the frequency domain and the time domain as compared with the classical elliptic function. In addition, the modified function exhibits better magnitude sensitivity properties than the classical function.     

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。     

A 4-MHz CMOS continuous-time filter with on-chip automatic tuning

A third-order elliptic low-pass continuous-time filter with a 4-MHz cutoff frequency, integrated in a 3-μm p-well CMOS process, is presented. The design procedure is based on the direct simulation of a doubly terminated LC ladder filter by capacitors and fully balanced, current-controlled transconductance amplifiers with extended linear range. The on-chip automatic tuning circuit uses a phase-locked loop implemented with an 8.5-MHz controlled oscillator that matches a specific two-integrator loop of the filter. The complete circuit features 70-dB dynamic range (THD<-50 dB) and consumes only 16 mW from ±2.5-V supplies     

Simulation of a novel current-mode universal filter using FDCCIIs

In this paper, a new current-mode universal active-RC filter is proposed. The proposed circuit is based on a new universal passive filter topology. This passive filter is generated from a classical well known current-mode universal passive filter applying a transformation procedure. Two Fully Differential Current Conveyors (FDCCII) are used to construct a universal active-RC filter from this passive filter. The FDCCII based proposed filter has only grounded resistors and capacitors as the passive elements. The circuit simultaneously provides the three basic filter characteristics, namely high-pass (HP), band-pass (BP) and low-pass (LP). SPICE simulation results are given to verify the theoretical analysis.     

Simplified MOS switched capacitor ladder filter structures

A general technique for time-sharing amplifiers to reduce die area in switched capacitor ladder filters is described and illustrated with a fifth-order elliptic low-pass ladder filter requiring only three operational amplifiers. Techniques for synthesizing filters with maximum passband accuracy in the presence of parasitic capacitances are presented, and verified with two versions of the same fifth-order design integrated in a standard NMOS process. Passband accuracies of better than 0.1 dB have been achieved using only 0.3 pF unit-sized capacitors. The dynamic range is 75 dB.     

Synthesis of dual behavior resonator (DBR) filters with integrated low-pass structures for spurious responses suppression

This paper deals with a rigorous synthesis of dual behavior resonator (DBR) filters with integrated low-pass filter for spurious response suppression. The basic low-pass filter consists in an L-C-L structure associating two transmission lines and an open-ended stub. After full definition, the synthesis is validated from comparisons between simulation- and experimental-data acquired with some third-order filters designed on alumina substrate.     

Design of Compact Low-Pass Elliptic Filters Using Double-Sided MIC Technology

A novel implementation of stepped-impedance low-pass elliptic filters is presented in this paper. The filters are based on the well-known technique of cascading high- and low-impedance sections to simulate the ladder LC lumped-circuit prototype. We propose in this study a new approach to build up the constitutive circuit elements by taking advantage of the use of both sides of the substrate. The use of double-sided technology yields both design flexibility and good circuit performance. High-impedance sections are achieved by using slots in the backside of the substrate, whereas low-impedance sections are obtained with parallel-plate capacitors. In order to achieve the transmission poles corresponding to the elliptic design, these capacitors are series connected to the ground plane by means of high-impedance coplanar-waveguide lines, which mainly act as inductors. As a final step, meandering techniques have been applied to the high-impedance sections of the filter to reduce the overall circuit size. The measurement of several fabricated filters shows fairly good agreement between theory and experiment     

Analysis of simple two-capacitor low-pass filters

The performance of typical low-pass capacitor filters is limited by the mutual inductance between the input and output sides of the filter. This paper describes how two appropriately spaced capacitors can be used to construct a low-pass filter with significantly better high-frequency performance than a one-capacitor filter. Laboratory measurements and numerical simulations are used to quantify the mutual inductance and compare the performance of one- and two-capacitor low-pass filters.     

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.     

MOS switched capacitor ladder filters

A new technique for designing precision, fully integrated, high-order filters using standard MOS technology is described. Switched capacitor integrators have been used to realize long time constants in small areas, and by interconnecting these integrators in a `leapfrog' configuration, monolithic high-order filters have been implemented with transfer functions that are very insensitive to component variations. Experimental results are presented for an NMOS fifth-order Chebyshev low-pass ladder filter with 0.1-dB passband ripple, a cutoff frequency of 3.4 kHz when clocked at 128 kHz, and a dynamic range of 83 dB. An efficient method for implementing transmission zeros is also presented, along with a complete design example, and additional experimental results for a third-order elliptic low-pass ladder filter which achieved 90-dB dynamic range, with a total power dissipation of 18 mW in a die area of 4400 mil/SUP 2/.     

Universal Current-Mode Active-C Filter Employing Minimum Number of Passive Elements

A universal current-mode active-C filter simultaneously realizing low-pass, band-pass and high-pass responses is proposed. The filter can also realize notch and all-pass responses with interconnection of relevant output currents. The presented filter employs four second-generation current controlled conveyors (CCCIIs) as active elements and only two capacitors as passive elements. The proposed active-C filter can be tuned electronically, and has low element sensitivities.