Design of linear combination of weighted medians

This paper introduces a novel nonlinear filtering structure: the linear combination of weighted medians (LCWM). The proposed filtering scheme is modeled on the structure and design procedure of the linear-phase FIR highpass (HP) filter in that the linear-phase FIR HP filter can be obtained by changing the sign of the filter coefficients of the FIR lowpass (LP) filter in the odd positions. The HP filter can be represented as the difference between two LP subfilters that have all positive coefficients. This representation of the FIR HP filter is analogous to the difference of estimates (DoE) such as the difference of medians (DoM). The DoM is essentially a nonlinear HP filter that is commonly used in edge detection. Based on this observation, we introduce a class of LCWM filters whose output is given by a linear combination of weighted medians of the input sequence. We propose a method of designing the 1-D and 2-D LCWM filters satisfying required frequency specifications. The proposed method adopts a transformation from the FIR filter to the LCWM filter. We show that the proposed LCWM filter can offer various frequency filtering characteristics including “LP,” “bandpass (BP),” and “HP” responses     

Log-domain synthesis of nth order universal filter

In this paper a synthesis approach for an nth-order universal log-domain filter comprising lowpass (LP), highpass (HP) and bandpass(BP) filtering functions is proposed. The approach is simple and the method of extending the approach to two uncommon filtering functions, lowpass notch (LPN) and high pass notch (HPN), is also given. The second, fourth and sixth-order universal log-domain filters are designed using log-exponential relationship between voltage and current of bipolar junction transistors (BJT) for the verification of approach. The performance of proposed universal filter and that of extended LPN and HPN was verified through simulation results.     

A step-by-step active-filter design

This article presents, in a simplified manner, a design method for active filters intended for those who are not filter specialists. By following the described five-step approach, a circuit designer who has some knowledge of passive filters will (without having to learn a whole new technology) be able to design active filters just as easily as he now handles conventional passive filters. Starting with the filter specification, it is shown sequentially how to realize a network that meets the prescribed requirements. Configurations and element values are given for the low-pass (LP), bandpass (BP), high-pass (HP), all-pass (AP), and band-elimination (BE), second-order active filter building blocks.     

Universal filters of arbitrary order and type employing square-root-domain technique

Novel Single Input Multiple Output (SIMO) and Multiple Input Single Output (MISO) universal filter topologies of arbitrary order and type are introduced in this paper. The proposed topologies have been realised by employing Square-Root Domain (SRD) technique. An offered benefit of the universal filter topologies is that only grounded capacitors are required for their implementations and the resonant frequency of the filters can be electronically controlled by an appropriate dc current. The proposed universal filters simultaneously offer all the five standard filtering functions i.e. Lowpass (LP), Highpass (HP) and Bandpass (BP), Bandstop (BS) and Allpass (AP) frequency responses. In addition, the SIMO topology is generic in the sense that it can yield four different stable filter configurations. Two design examples are provided in each configuration and the correct operation of the corresponding topologies has been evaluated through the PSPICE software with BSIM 0.35-µm CMOS process model parameters.     

All-Grounded Passive Elements Voltage-Mode DVCC-Based Universal Filters

In this paper two new voltage-mode (VM) universal filters employing three plus-type differential voltage current conveyors (DVCC+s) and grounded passive elements are presented. The first proposed filter is a single-input five-output (SIFO) circuit which can realize simultaneously all of the standard responses, i.e. low-pass (LP), band-pass (BP), high-pass (HP), all-pass (AP) and notch (NH) from the same configuration. The second proposed circuit is a three-input single-output (TISO) universal filter for realizing standard responses depending on the selection of the input signal from the same topology. Both of the proposed filters have the advantage of a high input impedance, which enables easy cascading to obtain higher order filters. The proposed filters are simulated using the SPICE program to verify the theoretical analysis.     

Decade Bandwidth Bias T's for MIC Applications up to 50 GHz (Short Paper)

A new design of bias T is described capable of carrying direct currents (dc) of a number of amperes while operating over RF bandwidths of more than a decade. Realized in microstrip or stripline, a design can operate up to at least 50 GHz as either a stand-alone component or as part of a microwave integrated circuit (MIC). The bias T circuit has been treated as a combination of HP, BP, and LP filters, the BP filter forming the major part. Design of the filter is by an exact transfer function synthesis procedure involving the application of the Richards transformation.     

NOVEL LINEAR TRANSFORMATION SWITCHED-CAPACITOR FILTER DESIGN

This paper presents a novel method that is applied to realize the Linear Transformation(LT)Switched-Capacitor Filter(SCF).It adopts the Voltage Control Voltage Source(VCVS)equalized transfor-mation to revise the original LC ladder filter and induce it into 16 basic sections and then extend the princi-ple of the LT in order to fit active and 3 port networks and give out switched-capacitor circuits corre-sponding to the 16 basic sections,which can realize all four kinds of filters——LP,HP,BP,BS filters.De-signed examples are given here.An Nth order filter only requires N amplifiers and the circuit is insensitive toparasitic capacitances.The experimental results of a 3rd order elliptic LP and a 6th order elliptic BP are giv-en and agree with the theory.     

Voltage-mode FDCCII-based universal filters

Three new voltage-mode universal biquadratic filters configuration are proposed. The first proposed high-input impedance universal filter with single input and five outputs, which can simultaneously realize voltage-mode lowpass (LP), bandpass (BP), highpass (HP), bandstop (BS) and allpass (AP) filter responses employing all grounded passive components. The second proposed high-input impedance universal filter with three input and single output, which also can realize all the standard filter functions without requiring any inverting input voltage signal. The third proposed universal filter with three inputs and five outputs, which can be used as either a three-input single-output or a two-input five-output universal filter. Moreover, each of the proposed circuits still enjoys (i) the employment of only grounded capacitors, and (ii) no requirement with the component choice conditions to realize specific filtering functions.     

A Low-Power 3V Lowpass OTA-C Filter for Megahertz Range

By applying a signal-flow graph (SFG) based filter synthesis an active OTA-C topology for integration of a 5-degree elliptic lowpass (LP) filter has been designed. The dynamic range has been maximized for this single-ended OTA-C filter, which has floating capacitors. This has been done through the use of an optimizing circuit simulator. Thus low-voltage (3V) operation despite high signal amplitudes (1V_pp) has been achieved. A linearized operational transconductance amplifier (OTA) has been designed and optimized for the filter. For comparison purposes the single-ended design has been converted to a fully differential one with an additional +6dB of gain. Integrated filters realized with a 1.2 m CMOS process have been thoroughly measured. The filters are especially applicable for mobile communications because of low power consumption.     

Design of Variable Two-Dimensional FIR Digital Filters by McClellan Transformation

In this paper, the technique of McClellan transformation is applied to design variable 2-D FIR digital filters. Compared with the conventional transformation, the 2-D transformation subfilter and the 1-D prototype filter are designed such that their frequency characteristics are adjustable. Moreover, they are tunable by the same variable parameter, so the variable characteristics of 1-D prototype filters are coincident with those of 2-D subfilters. Several examples, including variable fan filters, variable circularly symmetric filters, and variable elliptically symmetric filters with arbitrary orientation, are presented to demonstrate the effectiveness and the flexibility of the presented method.      

A New Current-Mode Synthesis Method for Dynamic Translinear Filters and its Applications in Hearing Instruments

A new current mode synthesis method for dynamic translinear filters is proposed. As a design example, we have considered an ultra-low power second order filter working in audio frequency range, for hearing aids application, and using subthreshold MOS devices. It has a nominal supply voltage of 1.2 V and works down to 1 Volt. It has a power consumption of 5 W. The filter cut-off frequency and its Q factor can be tuned respectively from 600 Hz to 13 kHz and from 0.6 to 1.1. Mismatch problems are investigated on the circuit level and an on-chip compensation method is proposed.     

A fast matrix iterative technique for the WLS design of 2-D quadrantally symmetic FIR filters

High computational complexity is a major problem encountered in the optimal design of two-dimensional (2-D) finite impulse response (FIR) filters. In this paper, we present an iterative matrix solution with very low complexity to the weighted least square (WLS) design of 2-D quadrantally symmetric FIR filters with two-valued weighting functions. Firstly, a necessary and sufficient condition for the WLS design of 2-D quadrantally symmetric filters with general nonnegative weighting functions is obtained. Then, based on this optimality condition, a novel iterative algorithm is derived for the WLS design problem with a two-valued weighting function. Because the filter parameters are arranged in their natural 2-D form and the transition band is not sampled, the computation amount of the proposed algorithm is reduced significantly, especially for high-order filters. The exponential convergence of the algorithm is established, and its computational complexity is estimated. Design examples demonstrating the convergence rate and solution accuracy of the algorithm, as well as the relation between the iteration number of the algorithm and the size and transition-band width of the filter are given.     

低功耗、低灵敏度有源带通滤波器设计的新方法

提出运用低通到带通的频率变换法与阻容细化法相结合的思想,直接利用2阶的低通(LP)滤波器原型电路实现4阶低功耗、低灵敏度的带通(BP)滤波电路的设计新方法。具体而言,通过对低通原型滤波电路进行阻抗变换以及时其对应的RC电路实现所谓“有损的LP-BP变换”,就可以实现带通(BP)滤波电路的设计。选用2阶切比雪夫(Chebyshev)低通滤波器电路为原型,给出4阶带通滤波器的具体设计过程,并通过PSpice软件来验证此种方法的可行性和实用性。     

Design of 1-D Stable Variable Fractional Delay IIR Filters

In this brief, a two-stage approach for the design of 1-D stable variable fractional delay infinite-impulse response (IIR) digital filters is proposed. In the first stage, a set of fixed delay stable IIR filters are designed by minimizing a quadratic objective function, which is defined by integrating error criterion with IIR filter stability constraint condition. Then, the final design is determined by fitting each of the fixed delay filter coefficients as a 1-D polynomial. Two design examples are given to show the effectiveness of the proposed design method     

Design of 2-D FIR narrow transition band filters by double transformations using GA approach

In this investigation, subfilters are cascaded in the design of a 2-D narrow transition band FIR digital filter with double transformations, a transformation from wide transition band subfilter into 1-D narrow transition band filter and a McClellan transformation from 1-D filter into 2-D filter. The traditional method for designing a 2-D FIR digital filter with a narrow transition band yields very high orders. The difficulty of the design and implementation will increase with orders exponentially. Numerous identical low-order subfilters are cascaded together to simplify the design of a high-order 2-D filter compared to traditional design method. A powerful genetic algorithm (GA) is presented to determine the best coefficients of the McClellan transformation. It can be used to design any contours of arbitrary shape for mapping 1-D to 2-D FIR filters very effectively. A generalized McClellan transformation is presented, and can be used to design 2-D complex FIR filters. Various numerical design examples are presented to demonstrate the usefulness and effectiveness of the presented approach.

Biquadratic filter sections employing a single current conveyor

LP, BP and HP filters with low passive component sensitivity and independently adjustable ?0 or Q are presented. In addition, two new types of current conveyor are introduced and a new current-conveyor classification is proposed.     

Design and analysis of MISO bi-quad active filter

ABSTRACT

In this paper, a multiple-input single-output (MISO) voltage-mode bi-quad active filter using voltage differencing voltage transconductance amplifier (VDVTA) is designed and analysed. The filter can realize several functions such as low-pass (LP), high-pass (HP), band-pass (BP), band-reject (BR) and all-pass (AP). The proposed configuration employs three input voltages and generates a single output voltage. The filter characteristics, i.e., pole frequency (ω_p) and quality factor (Q) are electronically tunable through the bias current of the VDVTA. The filter performance is analysed through sensitivity analysis in presence of parasitics as well as process, voltage and temperature fluctuations. The proposed design is implemented in a 45-nm CMOS technology and simulated using Virtuoso Analog Design Environment of Cadence.     

High Output Impedance Current-Mode Four-Function Filter with Reduced Number of Active and Passive Elements Using the Dual Output Current Conveyor

This paper reports a new single-input multi-output current-mode multifunction filter which can simultaneously realise LP, HP, BP and BR filter functions all at high impedance outputs. The circuit permits orthogonal adjustment of quality factor Q and ₀, employs only five grounded passive components and no element matching conditions are imposed. A second order all-pass function can easily be obtained. The passive sensitivities are shown to be low.     

Second-order OTA-C filters derived from Nawrocki-Klein biquad

Based on the Nawrocki and Klein biquad and using different input and output techniques, many new filter structures and functions are developed from both voltage- and current-mode viewpoints. For example, it is found that the basic five operational transconductance amplifier (OTA) structure has the LP, BP, HP, BS and AP functions without the use of capacitor injection and component matching, a feature shared by no other existing two integrator loop OTA-capacitor (OTA-C) circuit, including the original NK biquad. Various BS, LPN, HPN, AP and universal architectures are obtained, which require fewer OTAs and may be more useful than the original biquad. This research shows that the NK biquad is one of the most important second-order OTA-C filters at least from the viewpoint of filter architectures and functions, and thus should receive attention in continuous-time filter design     

A CMOS Monolithic Image-Reject Filter

A CMOS inductorless image-reject filter based on active RLC circuitry is discussed and designed with the emphasis on low-noise, low-power, and gigahertz-range circuits. Two -enhancement techniques are utilized to circumvent the low characteristics inherent in the simple feedback circuit. The frequency tuning is almost independent of tuning, facilitating the design of the automatic tuning circuitry. The stability and the tuning scheme of the filter are also discussed. Simulations using 0.6 m CMOS technology demonstrate the feasibility of the tunable image-reject filter for GSM wireless applications. Simulation results show 4.75 dB voltage gain, 9.5 dB noise figure, and –20 dBm IIP3 at a passband centered at 947 MHz. The image signal suppression is 60 dB at 1089 MHz and the power consumption is 27 mW.