ITERATED DESIGN OF NON EQUIRIPPLE LOW PASS FILTER

Non equiripple approximation of filter characteristics can be realized either odd order or even order in the symmetric load case.This paper presents a method of synthesizing non equiripple low pass filter based on iteration analysis,in which the rational fraction formed of Chebyshev polynomial is used as the filter characteristic function.This method is convenient for computer programming,because the attenuation zeros and poles of the filter can be determined easily and the synthesis procedure is simple,too.The given examples show that the method is of a practical value in filter design.

Multilayer Low Pass Filter Using LTCC Technology

The implementation and characteristics of a compact lumped-element three-order low pass filter are presented in this paper. The filter with 120 MHz cut off frequency, as well as more than 20 dB of the attenuation above 360 MHz frequency band is successfully manufactured in an LTCC substrate with 40 pm layer thickness. The overall size of the filter is 2.0 mm×1.2 mm×0.9 mm. A good coincidence between the measured results and the full-wave electromagnetic designed responses is observed.

Maximum Power Point Tracking With Fractional Order High Pass Filter for Proton Exchange Membrane Fuel Cell

Proton exchange membrane fuel cell (PEMFC) is widely recognized as a potentially renewable and green energy source based on hydrogen. Maximum power point tracking (MPPT) is one of the most important working conditions to be considered. In order to improve the performance such as convergence and robustness under disturbance and uncertainty, a fractional order high pass filter (FOHPF) is applied for the MPPT controller design based on the traditional extremum seeking control (ESC). The controller is designed with integerorder integrator (IO-I) and low pass filter (IO-LPF) together with fractional order high pass filter (FOHPF), by substituting the normal HPF in the original ESC system. With this FOHPF ESC, better convergence and smoother performance are achieved while maintaining the robust specifications. First, tracking stability is discussed under the commensurate-order condition. Then, simulation results are included to validate the proposed new FOHPF ESC scheme under disturbance. Finally, comparison results between FOHPF ESC and the traditional ESC method are also provided. © 2014 Chinese Association of Automation.

Design of active disturbance rejection internal model control strategy for SISO system with time delay process

A novel control scheme of active disturbance rejection internal model control(ADRIMC) is proposed to improve the anti-interference ability and robustness for the dead-time process. The active anti-interference concept is introduced into the internal model control(IMC) by analyzing the relationship between IMC and disturbance observer control(DOB). Further, a design process of disturbance filter is presented to realize the active anti-interference ability for ADRIMC scheme. The disturbance filter is used to estimate an equivalent disturbance consisting of both external disturbances and internal disturbances caused by model mismatches.Simulation results demonstrate that the proposed method possesses a good disturbance rejection performance, though losing some partial dynamic performance. In other words, the proposed method shows a tradeoff between the dynamic performance and the system robust.

DENOISING METHODS IN INTERFEROMETRIC SAR IMAGES PROCESSING

Thermal and “Speckle” noise is an obstacle to generate the digital elevation model(DEM) from interferogram by 2 D SAR images. According to the theory of interferometry, the main sources of noise in interferogram are discussed. On the basis of the character of noise in the interferogram, the low pass filter, median filter and wavelet transform are investigated. Wavelet transform is forwarded as the most effective method to eliminate the InSAR noise because it can keep the resolution of the images during eliminating the noise. The raw data verify the validity and effectiveness of wavelet transform.

Development of series SQUID array with on-chip filter for TES detector

A cold preamplifier based on superconducting quantum interference devices(SQUIDs)is currently the preferred readout technology for the low-noise transition edge sensor(TES).In this work,we have designed and fabricated a series SQUID array(SSA)amplifier for the TES detector readout circuit.In this SSA amplifier,each SQUID cell is composed of a first-order gradiometer formed using two equally large square washers,and an on-chip low pass filter(LPF)as a radiofrequency(RF)choke has been developed to reduce the Josephson oscillation interference between individual SQUID cells.In addition,a highly symmetric layout has been designed carefully to provide a fully consistent embedded electromagnetic environment and achieve coherent flux operation.The measured results show smooth V-Φcharacteristics and a swing voltage that increases linearly with increasing SQUID cell number N.A white flux noise level as low as 0.28μφ;/Hz;is achieved at 0.1 K,corresponding to a low current noise level of 7 pA/Hz;.We analyze the measured noise contribution at mK-scale temperatures and find that the dominant noise derives from a combination of the SSA intrinsic noise and the equivalent current noise of the room temperature electronics.

A reconfigurable active-G_m-RC filter formultistandard wireless receivers

A 4th-order low-pass filter （LPF） based on active-Gm-RC structure for multi-standard system application is presented in this paper. The performances of LPF are controlled by a 1-bit control- voltage, and the cut-off frequency, channel selectivity, and linearity of the proposed filter can be reconfigured accordingly. In order to improve the accuracy of the cut-off frequency, a binary-weigh- ted switched-capacitor array is employed as the auto-tuning circuits to calibrate the RC-time con- stant. Fabricated in TSMC 0. 18μm RF CMOS process, the proposed LPF achieves a measured cutoff frequency of 1.95 and 12.3MHz for WCDMA and GPS/Galileo application with a bandwidth de viation less than 4%. The measured l dB compression points are -3.0dBm and -5.1 dBm respectively for different modes. The core circuit of LPF consumes l mW and 1.6mW for WCDMA and GPS/Galileo respectively. And the proposed LPF occupies an area of 0.78ram2.

A low power high linearity baseband for a direct conversation CMMB tuner

An analog baseband circuit made in a 0.35-μm SiGe BiCMOS process is presented for China Multi-media Mobile Broadcasting（CMMB） direct conversion receivers.A high linearity 8th-order Chebyshev low pass filter（LPF） with accurate calibration system is used.Measurement results show that the filter provides 0.5-dB pass-band ripple,4% bandwidth accuracy,and-35-dB attenuation at 6 MHz with a cutoff frequency of 4 MHz.The current steering type variable gain amplifier（VGA） achieves more than 40-dB gain range with excellent temperature compensation.This tuner baseband achieves an OIP3 of 25.5 dBm,dissipates 16.4 mA under a 2.8-V supply and occupies 1.1 mm^2 of die size.

FIFA-Fast Interpolation and Filtering Algorithm for Calculating Dyadic Green’s Function in the Electromagnetic Scattering of Multi-Layered Structures

The dyadic Green’s function in multi-layer structures for Maxwell equations is a key component for the integral equation method,but time consuming to calculate.A novel algorithm,the Fast Interpolation and Filtering Algorithm(FIFA),for the calculation of the dyadic Green’s function in multi-layer structures is proposed in this paper.We discuss in specific details,ready for use in practical calculations of scattering in layer media,how to apply FIFA to calculate various components of the dyadic Green’s function.The algorithm is based on two techniques:interpolation of Green’s function both in the spectral domain and spatial domain,and low pass filter window based acceleration.Compared to the popular Complex Image Method(CIM),FIFA provides the same speed and overcomes several difficulties associated with CIM while being more general and robust.Specifically,there are no limitations on the frequency range,the number of layers in the structure and the type of Green’s functions to be calculated,and moreover,no need to extract surface wave poles from the spectral form of the Green’s function.Numerical results are given to demonstrate the efficiency and robustness of the proposed method.

Dyadic Bivariate Wavelet Multipliers in L^2（R@2）

The single 2 dilation wavelet multipliers in one-dimensional case and single A-dilation （where A is any expansive matrix with integer entries and [detA[ = 2） wavelet multipliers in twodimen- sional case were completely characterized by Wutam Consortium （1998） and Li Z., et al. （2010）. But there exist no results on multivariate wavelet multipliers corresponding to integer expansive dilation matrix with the absolute value of determinant not 2 in L^2（R^2）. In this paper, we choose 2I2 = （02 20 ） as the dilation matrix and consider the 212-dilation multivariate wavelet ψ = {ψ1, ψ2, ψ3 } （which is called a dyadic bivariate wavelet） multipliers. Here we call a measurable function family f ={fl, f2, f3} a dyadic bivariate wavelet multiplier if ψ1 = （F^-1（f1ψ1）,F^-1（f2ψ2）, F-l（f3ψ3）} is a dyadic bivariate wavelet for any dyadic bivariate wavelet ψ = {ψ1, ψ2, ψ3}, where f and F^- 1 denote the Fourier transform and the inverse transform of function f respectively. We study dyadic bivariate wavelet multipliers, and give some conditions for dyadic bivariate wavelet multipliers. We also give concrete forms of linear phases of dyadic MRA bivariate wavelets.

A multi-standard active-RC filter with accurate tuning system

A low-power, highly linear, multi-standard, active-RC filter with an accurate and novel tuning architecture is presented. It exhibits IEEE 802.11 a/b/g （9.5 MHz） and DVB-H （3 MHz, 4 MHz） application. The filter exploits digitally-controlled polysilicon resistor banks and a phase lock loop type automatic tuning system. The novel and complex automatic frequency calibration scheme provides better than 4 corner frequency accuracy, and it can be powered down after calibration to save power and avoid digital signal interference. The filter achieves OIP3 of 26 dBm and the measured group delay variation of the receiver filter is 50 ns （WLAN mode）. Its dissipation is 3.4 mA in RX mode and 2.3 mA （only for one path） in TX mode from a 2.85 V supply. The dissipation of calibration consumes 2 mA. The circuit has been fabricated in a 0.35μm 47 GHz SiGe BiCMOS technology; the receiver and transmitter filter occupy 0.21 mm^2 and 0.11 mm^2 （calibration circuit excluded）, respectively.

An Improved Frequency Synchronizer for Mobile OFDMSystems

Orthogonal Frequency Division Multiplexing （ OFDM） system is sensitive to Carrier Frequency Offset （ CFO ）. In this paper, traditional Maximum Likelihood Estimators （MLE） for CFO of OFDM are introduced first. Then, averaging method and a-filter are introduced as Low Pass Filter （LPF） to improve the performance of cyclic prefix estimator. The bandwith of LPF is determined by the coherence time of radio channel. Estimation performance in multipath channel is analyzed. Outlier picking-out scheme is proposed to improve performance further. Performance of close-loop structure is presented briefly, which is worse than that of open-loop structure. Finally, a parallel switch structure of frequency synchronizer is proposed for mobile OFDM systems. The scheme ezcploits training sequence and cyclic prefix. The proposed synchronizer has a wide acquisition range. It is accurate and robust in both AWGN channel and multipath channels. The complexity is low due to functionality of a-filter. A better performance of frequevlcy synchronization is obtained comparing to that of existing Maximum Likelihood Estimator（ MLEs）. We achieve these advantages without loss of bandwidth efficiency.

A 2.5-V 56-mW baseband chain in a multistandard TV tuner for mobile and multimedia applications

This paper presents post-layout simulated results of an analog baseband chain for mobile and multimedia applications in a 0.13-μm SiGe BiCMOS process.A programmable 7th-order Chebyshev low pass filter with a calibration circuit is used in the analog baseband chain,and the programmable bandwidth is 1.8/2.5/3/3.5/4 MHz with an attenuation of 26/62 dB at offsets of 1.25/4 MHz.The baseband programmable gain amplifier can achieve a linear 40-dB gain range with 0.5-dB steps.Design trade-offs are carefully considered in designing the baseband circuit,and an automatic calibration circuit is used to achieve the bandwidth accuracy of 2%.A DC offset cancellation loop is also introduced to remove the offset from the layout and self-mixing,and the remaining offset voltage is only 1.87 mV.Implemented in a 0.13-μm SiGe technology with a 0.6-mm2 die size,this baseband achieves IIP3 of 23.16 dBm and dissipates 22.4 mA under a 2.5-V supply.

A 264 MHz CMOS G_m-CLPF for ultra-wideband standard

A 264 MHz CMOS 4th Gm-C LPF target for the UWB standard is presented.The filter is designed by cascading two biquad cells.Compared with the previously published biquad cells,the biquad proposed here saves 1 transconductor,3 CMFB networks and 2 capacitors.Benefiting from these merits,the power consumption and chip area of the 4th order UWB LPF are reduced dramatically without other characteristics being affected.The LPF is designed and fabricated with TSMC 0.18μm 1P6M CMOS technology.The implemented LPF achieves a power gain of -0.5 dB.The measured frequency response matches well with that of the simulating results.The core chip area is only 0.06 mm2,which has a wonderful advantage over those from similar work.The LPF excluding test-buffers dissipates a total current of 3 mA from the 1.8 V power supply.

The Characterization of Parseval Frame Wavelets

In this paper,we characterize all generalized low pass filters and MRA Parseval frame wavelets in L 2 （R n ） with matrix dilations of the form （Df）（x） =√ 2f（Ax）,where A is an arbitrary expanding n × n matrix with integer coefficients,such that ｜det A｜ = 2.We study the pseudo-scaling functions,generalized low pass filters and MRA Parseval frame wavelets and give some important characterizations about them.Furthermore,we give a characterization of the semiorthogonal MRA Parseval frame wavelets and provide several examples to verify our results.