On the realization of an all-pass or a notch filter

It is shown that it is possible to realize either a second-order all-pass or a notch filter by a structure consisting of a grounded operational amplifier and two RC one-ports, Y1=G1+sC1and Y2=[R2+(1/sC2)]^-1. It is also shown that these filters may be realized by the same structure with Y1and Y2interchanged. These realizations possess minimum sensitivity with respect to the amplifier gain.     

An analog notch filter for piezoelectric optical scanner

The optical scanner is one of the most important components in free-space optical communications,airborne and space-based lidars,adaptive optics,and so on.The performance of an optical scanner is frequently limited by the presence of mechanical resonances.This paper presents an analog notch filter with adjustable function to reject the mechanical resonances of the optical scanner.First of all,the structure and work principle of the piezoelectric optical scanner are introduced.Furthermore,the frequency sweep method based on virtual instruments is used to gain the natural frequency of the piezoelectric optical scanner.Then,the notch filters in series are used to reduce the oscillation of the scanner at the resonance frequencies.A variety of scanning experiments were carried out.After the introduction of the notch filter,the non-linearity was reduced to±1.1% from ±2.1%.The linearity performance was greatly improved.     

97dB动态范围、带温度补偿的MEMS电容传感器读出电路

This paper presents a charge-sensitive-amplifier(CSA)based readout circuit for capacitive microelectro-mechanical-system(MEMS)sensors.A continuous-time(CT)readout structure using the chopper technique is adopted to cancel the low frequency noise and improve the resolution of the readout circuits.An operational trans-conductance amplifier(OTA)structure with an auxiliary common-mode-feedback-OTA is proposed in the fully differential CSA to suppress the chopper modulation induced disturbance at the OTA input terminal.An analog temperature compensation method is proposed,which adjusts the chopper signal amplitude with temperature variation to compensate the temperature drift of the CSA readout sensitivity.The chip is designed and implemented in a 0.35 m CMOS process and is 2.1 2.1 mm2in area.The measurement shows that the readout circuitachieves0.9aF/√Hz capacitive resolution,97dBd ynamic range in 100Hz signal bandwidth,and 0.8mV/fF sensitivity with a temperature drift of 35 ppm/℃ after optimized compensation.     

Resistorless first-order all-pass filter with electronic tuning

A first-order all-pass filter (APF) with electronic tuning properties is presented. The filter consists of only active components and a single-grounded capacitor. The circuit is cascadable, has small sensitivities, and suitable for monolithic integration, and it can also operate at high frequencies.     

High dynamic range image rendering with a Retinex-based adaptive filter.

We propose a new method to render high dynamic range images that models global and local adaptation of the human visual system. Our method is based on the center-surround Retinex model. The novelties of our method is first to use an adaptive filter, whose shape follows the image high-contrast edges, thus reducing halo artifacts common to other methods. Second, only the luminance channel is processed, which is defined by the first component of a principal component analysis. Principal component analysis provides orthogonality between channels and thus reduces the chromatic changes caused by the modification of luminance. We show that our method efficiently renders high dynamic range images and we compare our results with the current state of the art.     

Realization of all-pass and notch filters using a single current conveyor

A novel network for realizing an all-pass transfer function using a single current conveyor is proposed. The network has high input impedance, this permits to use the networks in cascade without any requiring impedance matching device. By tuning a resistor, the network also realizes a notch filter.     

一种具有较大电容动态测量范围的接口电路

针对应用广泛的电容式传感器信号采集问题,提出了一种具有较大电容动态测量范围的高精度电容式传感器接口电路。该接口电路包括一个电容式有源电桥,以及用于将电容直接转换为频率的张弛振荡器,电路的频率输出用于确定微湿度传感器的响应特性。在基于薄膜的电容湿度传感器上进行了测试,实验结果表明,相比现有的类似电路设计,提出电路的结构更加简单且具有更大的电容测量范围和较高的精度,在1 p-600 p测量范围内的精度（误差百分比）<-2.14%,接口电路灵敏度为4.91 Hz/ppm,且输出频率与电容变化成线性关系。     

Active all-pass filter using a differential operational amplifier

A circuit is presented for a first-order active all-pass filter using a single differential operational amplifier. The form of the transfer function is T(p) = (1 ? p)/(1 + p).     

Component reduced all-pass filter with a grounded capacitor and high-impedance input

In the literature, opportunities of the current conveyors with reduced current gains are not adequately emphasised for filter designs. In this study, we show a new all-pass filter (APF) possibility using a current conveyor with half current gain. Although many first-order voltage mode APFs were proposed, most of them either cannot provide high input impedance and grounded capacitor features together or they provide these features with components more than necessary. The presented circuit provides both of these features using reduced number of elements. Spice simulation and experimental results are given to verify the theoretical results.     

CMOS selfbiased Euclidean distance computing circuit with high dynamic range

A CMOS analogue circuit is proposed that computes the Euclidean distance between two vectors whose coefficients are represented by currents. The circuit is selfbiased, requires only a small number of transistors, and offers good accuracy over a wide range of input values.<>     

Tunable/adaptive second-order IIR notch filter

A modified second-order infinite impulse response (IIR) notch filter with constrained poles and zeros is presented to eliminate or retrieve sinusoids embedded in a broadband signal. Such a filter is ideally suited to either parallel or cascaded implementation. Two classes of problems are considered. The first is where the sinusoidal frequencies are known a priori. For this case a straightforward design procedure based on a set of design characteristic graphs is used to select tunable notch filter parameters. An interesting property of the notch filter model is that it can be converted to a line enhancer by interchanging the position of the poles and zeros. The second type of problem arises when the sinusoidal frequencies are unknown and possibly varying with time. This means that an adaptive solution is required and an important consideration is the parameter estimation accuracy. For this purpose, the paper derives the Cramer–Rao lower bound for the adaptive cascaded notch filter using a frequency-domain approach. Some simulation results are included to demonstrate the effectiveness of the proposed adaptive notch filter.     

Arrayed waveguide dynamic gain equalization filter with reducedinsertion loss and increased dynamic range

We present an arrayed waveguide dynamic gain equalization filter with less than 4.5-dB insertion loss and greater than 14-dB dynamic range over the C-band resulting from three improvements: a circulator and polarization splitter combined into one, used to make the device polarization insensitive; segmentation in the star coupler transition regions; and an exponential control wavelength distribution     

Design of a high-frequency notch filter

Design equations for a high-frequency notch filter are presented. The filter makes use of a hybrid coil for decoupling input from output. The notch is obtained from a bridge-type balance, and can be made quite narrow.     

Low-voltage first-order fully differential CMOS all-pass filter with programmable pole-zero

A simple modification of the conventional first-order all-pass filter is introduced that provides it with a low-voltage fully differential operation with programmable pole-zero frequency. The modification is based on the inverting op-amp configuration and uses operational transconductance amplifiers instead of resistors not needing a buffered signal source or buffered op-amps as the conventional all-pass does. Experimental results verify that tuning capability is provided.     

The digital all-pass filter: a versatile signal processing buildingblock

The properties of digital all-pass filters are reviewed and a broad overview of the diversity of applications in digital filtering is provided. Starting with the definition and basic properties of a scalar all-pass function, a variety of structures satisfying the all-pass property are assembled, with emphasis placed on the concept of structural losslessness. Applications are then outlined in notch filtering, complementary filtering and filter banks, multirate filtering, spectrum and group-delay equalization, and Hilbert transformations. In all cases, the structural losslessness property induces very robust performance in the face of multiplier coefficient quantization. Finally, the state-space manifestations of the all-pass property are explored, and it is shown that many all-pass filter structures are devoid of limit cycle behavior and feature very low roundoff noise gain     

Enhanced linear dynamic range of asymmetric Fabry-Pe/spl acute/rot modulator/detector

An InGaAsP multiple-quantum-well asymmetric Fabry-Pe/spl acute/rot modulator/detector has been developed for radio-over-fiber systems. The measured bandwidth is more than 6 GHz and the total insertion loss is 7.1 dB. The property of nonlinearity and spurious-free dynamic range (SFDR) has been studied theoretically. By optimizing the operation optical wavelength and bias voltage based on the numerical simulation, fifth-order nonlinearity dominates the intermodulation distortion and an SFDR of 101 dB/spl middot/Hz/sup 4/5/ has been achieved experimentally.     

A convex macromodeling of dynamic comparator for analog circuit synthesis

Equation-based circuit optimization using geometric programming (GP) is a promising analog and mixed-signal design framework that is inherently capable of hierarchical design synthesis. By taking a dynamic comparator as a test vehicle, this paper presents a reduced-complexity cell-level macromodeling method compatible with equation-based circuit optimization using GP. A key contribution of this paper is the demonstration of the complexity-reduction method in creating a convex, empirical, and cell-level macromodel. The variable space reduction is guided by the 1st-order modeling obtained from fundamental understandings on the circuit behavior. The proposed modeling is ideally applicable to create a macromodel exhibiting nonlinear behaviors in time-domain, which are not readily captured in a traditional equation-based modeling approach. The numerical experiment using a dynamic comparator in 0.13 μm CMOS process as a test vehicle indicates that the modeling errors for major performance metrics are less than 5 %, while obtained Pareto-front tradeoff provides useful design guidelines on the architecture-level design exploration.     

超声成像仪动态滤波器设计

针对超声在人体中传播能量随深度增加而衰减的特点,为了提高图像分辨率,设计了一种应用于超声成像系统中动态滤波器电路。文中给出了滤波器的硬件设计电路图,通过电路测试证明该设计简单可行,对回波信号进行匹配滤波,得到最佳的信噪比,满足系统设计要求。     

A wide dynamic range analog predistortion-type linearizer using self-cancellation scheme

A new radio frequency linearized power amplifier (LPA) system for wideband-code-division-multiple-access (WCDMA) application is demonstrated. The main amplifier is a parallel combination of drive amplifiers, and the same type of drive amplifier is also used to generate the predistortion signal. Self-cancellation of the intermodulation-distortion (IMD) components is obtained by the generic identity between the nonlinear characteristics of the main amplifier and the predistortion signal, both of which are originated from the same type of devices. Such self-cancellation scheme exhibits the improvement of 13 dB in the adjacent channel leakage ratio (ACLR) for WCDMA signal excitation.