Showing papers on "Butterworth filter published in 2012"

Widely Tunable 4th Order Switched G $_m$ -C Band-Pass Filter Based on N-Path Filters

Abstract: A widely tunable 4th order BPF based on the subtraction of two 2nd order 4-path passive-mixer filters with slightly different center frequencies is proposed. The center frequency of each 4-path filter is slightly shifted relative to its clock frequency (one upward and the other one downward) by agm-C technique. Capacitive splitting of the input signal is used to reduce the mutual loading of the two 4-path BPFs and increase their quality factors. The filter is tunable from 0.4 GHz to 1.2 GHz with approximately constant bandwidth of 21 MHz. The in-band 1-dB compression point of the filter is -4.4 dBm while the in-band IIP3 of the filter is +9 dBm and the out-of-band IIP3 is + 29 dBm (Δf=+50 MHz). The ultimate rejection of the filter is >; 55 dB and the NF of the filter is 10 dB. The static and dynamic current consumption of the filter are 2.8 mA from 2.5 V and 12 mA from 1.2 V, respectively (at 1 GHz). The LO leakage power to the input port is <; - 60 dBm. The filter has been fabricated in CMOS LP 65 nm technology and the active area is 0.127 mm2.

Improved amplitude- and phase-scintillation indices derived from wavelet detrended high-latitude GPS data

Abstract: Accuracy and validity of scintillation indices estimated using the power and phase of the GPS signal depend heavily on the detrending method used and the selection of the cutoff frequency of the associated filter. A Butterworth filter with a constant cutoff frequency of 0.1 Hz is commonly used in detrending GPS data. In this study, the performance of this commonly used filter is evaluated and compared with a new wavelet-based detrending method using GPS data from high latitudes. It was observed that in detrending high-latitude GPS data, a wavelet filter performed better than Butterworth filters as the correlation between amplitude- and phase-scintillation indices in S 4 and ? ? improved significantly from 0.53, when using a Butterworth filter, to 0.79, when using the wavelet filtering method. We also introduced an improved phase-scintillation index, ? CHAIN, which we think is comparatively a better parameter to represent phase scintillations at high latitudes as the correlation between S 4 and ? CHAIN was as high as 0.90. During the analysis, we also noted that the occurrence of the "phase scintillation without amplitude scintillation" phenomenon was significantly reduced when scintillation indices were derived using the wavelet-based detrending method. These results seem to indicate that wavelet-based detrending is better suited for GPS scintillation signals and also that ? CHAIN is a better parameter for representing GPS phase scintillations at high latitudes.

Switchless Tunable Bandstop-to-All-Pass Reconfigurable Filter

Abstract: The theory of a new type of bandstop-to-all-pass reconfigurable filter is developed in this work. A bandstop filter structure with both source-to-load and inter-resonator coupling is implemented. The synthesis equations are manipulated such that the signals in the filter's resonators and source-to-load transmission line can be made to constructively or destructively interfere at the output port through tuning of the resonant frequency of the filter's resonators. The relationship between resonator quality factor, filter bandwidth, and the all-pass response state is shown for the first time. The theory is proven through fabrication of a bandstop-to-all-pass filter with resonator unloaded quality factors greater than 500. Measured results show that the filter can continuously tune from insertion loss of 2.1 dB in the all-pass state to insertion loss of 69 dB in the bandstop state at the center frequency of the filter. Analog tuning of the attenuation level is also shown. The capability to switch from an all-pass to a variable-attenuation bandstop response enables a spectrally aware system to operate over wide bandwidths when interference levels are low and to dynamically add bandstop responses when interference affects its performance or signal equalization is required.

Single passband microwave photonic filter with wideband tunability and adjustable bandwidth

Abstract: A new and simple structure for a single passband microwave photonic filter is presented. It is based on using an electro-optical phase modulator and a tunable optical filter and only requires a single wavelength source and a single photodetector. Experimental results are presented that demonstrate a single passband, flat-top radio-frequency filter response without free spectral range limitations, along with the capability of tuning the center frequency and filter bandwidth independently.

Radiation Suppression for Cable-Attached Packages Utilizing a Compact Embedded Common-Mode Filter

Abstract: A compact and wideband common-mode filter is newly proposed to embed in a cable-attached printed circuit board (PCB) or packages for the suppression of the common-mode noise and its resulting electromagnetic interference (EMI) emission from the attached cable. The proposed filter consists of a pair of distributed signal lines on the top of a mushroom-like structure. Owing to its symmetry, an equivalent circuit model is developed and applied efficiently for this filter design. As an example, a filter prototype is designed and fabricated on a multilayer PCB. The filter prototype shows that it can greatly reduce the common-mode noise over 10 dB from 1.65 to 5.2 GHz. In addition, the corresponding fractional bandwidth is over 100% while the electrical size of the prototype is only 0.11 × 0.11 λg, where λg is the wavelength of the central frequency of its stopband. Also in the time domain, this filter prototype can reduce over 60% of the unintended noise. More importantly, the differential-signal integrity, in terms of the insertion loss in the frequency domain and the eye diagram in the time domain, is maintained up to 7 GHz. To the best of our knowledge, it is the first embedded common-mode filter proposed for gigahertz differential signals with such a large bandwidth and the most compact size. To further demonstrate the ability of the filter to suppress the common-mode current on the attached cable and the corresponding EMI emission, a test board design is also introduced and realized. From the experimental results related to this test board, a 10-dB suppression on average is indeed achieved.

Synthesis Methodology Applied to a Tunable Patch Filter With Independent Frequency and Bandwidth Control

Abstract: A new methodology for the synthesis of tunable patch filters is presented. The methodology helps the designer to perform a theoretical analysis of the filter through a coupling matrix that includes the effect of the tuning elements used to tune the filter. This general methodology accounts for any tuning parameter desired and was applied to the design of a tunable dual-mode patch filter with independent control of center frequency and bandwidth (BW). The bandpass filter uses a single triangular resonator with two etched slots that split the fundamental degenerate modes and form the filter passband. Varactor diodes assembled across the slots are used to vary the frequency of each degenerate fundamental mode independently, which is feasible due to the nature of the coupling scheme of the filter. The varactor diode model used in simulations, their assembling, the dc bias configuration, and measured results are presented. The theory results are compared to the simulations and to measurements showing a very good agreement and validating the proposed methodology. The fabricated filter presents an elliptic response with 20% of center frequency tuning range around 3.2 GHz and a fractional BW variation from 4% to 12% with low insertion loss and high power handling with a 1-dB compression point higher than .

Lumped-Element Realization of Absorptive Bandstop Filter With Anomalously High Spectral Isolation

Abstract: In this paper, we show a new absorptive banstop filter topology that is capable of creating large attenuation using low-Q small-size resonators. In addition, the implementation of a lumped-element absorptive bandstop filter is shown for the first time. Compared with the conventional absorptive filter structure, the new absorptive filter structure is smaller in size because there is no quarter-wavelength transmission line between two resonators and the resonators are lumped elements. For verification of the new topology, a lumped-element low-temperature co-fired ceramic (LTCC) bandstop filter with low-Q resonators has been designed and measured. Theory, simulation, and measurement showed good agreement between them, and the measurement showed 60-dB attenuation level at the center frequency. This attenuation level of the absorptive bandstop filter is 50 dB larger than the one obtained from the reflective bandstop filter with the same Q-factor and bandwidth. The small size and absorptive nature of the filter allow us to cascade the filters to create many different filter responses. It is shown that the lumped-element implementation makes the filter very amenable to realization of higher order responses in small form factors.

Design of compact microstrip lowpass filter with ultra-wide stopband

Abstract: A new microstrip lowpass filter with compact size and an ultra-wide stopband is proposed. To achieve compact size and ultra-wide band rejection, both triangular patch resonators and radial patch resonators are introduced in the filter. To reduce the circuit size of the filter further, meander transmission lines are also adopted in the design. A demonstration filter with 3 dB cutoff frequency at 1 GHz has been designed, fabricated and measured. Results indicate that the proposed filter can suppress the sixteenth harmonic response referred to a suppression degree of 15 dB. Furthermore, the proposed filter exhibits a small size of 0.111 λg×0.091 λg, where λg is the guided wavelength at 1 GHz.

A Low-Power and High-Precision Programmable Analog Filter Bank

Abstract: Analog filter banks befit remote audio- and vibration-sensing applications, which require frequency analysis to be performed with low-power consumption and with moderate-to-high precision. The precision of a filter bank depends on both the signal-path precision (i.e., dynamic range) and also the parameter precision (e.g., accuracy of the center frequencies). This brief presents a new bandpass filter for audio-frequency filter banks and provides a procedure for designing this filter. The filter is used in a 16-channel filter bank which has been fabricated in a 0.35- CMOS process. This filter bank has a dynamic range exceeding 62 dB and consumes only 63.6 when biased for speech frequencies. The filter bank's parameters are set via floating-gate current sources. This brief shows how to use these floating gates to obtain a versatile filter bank that can be precisely reprogrammed to arbitrary filter spacings and frequency weightings, with a parameter accuracy exceeding 99%.

Multi-Layered Dual-Band Bandpass Filter Using Stub-Loaded Stepped-Impedance and Uniform-Impedance Resonators

Abstract: The design of multi-layered dual-band bandpass filter using stub-loaded stepped-impedance and uniform-impedance resonators is proposed. The filter is designed to have dual-passband at 2.4, and 5.2 GHz for Wireless Local Area Network (WLAN). The multi-layered filter consists of the stub-loaded stepped-impedance resonator (SL-SIR) on the top layer and the stub-loaded uniform-impedance resonator (SL-UIR) on the bottom layer, that can provide the multi-path propagation to enhance the filter performance and compact circuit size. The proposed SL-SIR and SL-UIR play important roles for controlling the transmission zeros at each first and second passband edges. The measured results are in good agreement with the full-wave electromagnetic simulation results.

Power-Scalable, Complex Bandpass/Low-Pass Filter With I/Q Imbalance Calibration for a Multimode GNSS Receiver

Abstract: A power-scalable reconfigurable filter with in-phase/quadrature (I/Q) imbalance calibration for a multimode Global Navigation Satellite Systems (GNSS) receiver is presented. The filter is reconfigurable as either a fifth-order complex bandpass filter exhibiting a tunable intermediate frequency (4.092, 6.138, 10.23, 12.296, 13.29, 18.4, and 20.442 MHz) and bandwidth (2.2, 4.2, 8, 10, and 18 MHz) or a third-order low-pass filter with tunable bandwidth (5 and 9 MHz). A flexible current-reuse operational amplifier with a power-scaling technique is proposed to lower the power consumption, and the image-rejection ratio is improved by almost 20 dB by introducing an I/Q imbalance calibration circuit before the filter. The filter, which was implemented in 65-nm CMOS, consumes 2.9-19.5 mW in different modes, with the I/Q calibration circuit consuming 0.9 mW.

A Compact and Embedded Balanced Bandpass Filter With Wideband Common-Mode Suppression on Wireless SiP

Abstract: A compact balanced bandpass filter is proposed using a novel circuit topology, which includes a differential resonator and a common resonator in the conventional quasi-lumped coupled-line circuit, instead of adopting quarter-wavelength or half-wavelength transmission lines in the filter design. Based on this circuit topology, the balanced bandpass filter can support bandpass filtering function under differential-mode operation and exhibit bandstop filtering function under common-mode noise. By employing the advantage of the low-temperature co-fired ceramic fabrication technology, a compact balanced bandpass filter is centered at 3.42 GHz with fractional bandwidth 10.4% for differential signals and rejection band is from 1.48 to 7.4 GHz for the common-mode noise. Moreover, the proposed filter is able to introduce a transmission zero with excellent common-mode suppression (>;40 dB) within the differential-mode passband. The electrical size of this filter is 5.6 × 5.4 mm with the corresponding electrical size 0.113 × 0.109 λg, where λg is the guided wavelength at the center frequency 3.42 GHz. This compact balanced bandpass filter is suitable to be applied to the system-in-package technology for wireless application.

Adaptive-Differential-Evolution-Based Design of Two-Channel Quadrature Mirror Filter Banks for Sub-Band Coding and Data Transmission

Abstract: This paper proposes an improved and adaptive variant of the differential evolution algorithm for the design of two-channel quadrature mirror filters with linear phase characteristics. To match the ideal system response characteristics, the algorithm is employed to optimize the values of the filter bank coefficients. The filter response is optimized in both passband and stopband. The overall filter bank response aims at minimizing objectives like reconstruction error, mean square error in passband, and mean square error in stopband. Effective designing can be achieved by efficiently minimizing the objective function. The proposed algorithm is able to perform better than the other existing design methods. Five different design examples are presented to validate the effectiveness of the proposed approach over other conventional design techniques, as well as state-of-the-art evolutionary algorithms found in the literature.

Millimeter-wave liquid-crystal-based tunable bandpass filter

Abstract: For the first time, a tunable parallel-coupled microstrip lines filter based on nematic liquid crystals (LC) substrate for applications at mm-wave frequencies is presented. This 33 GHz filter has three-poles, about 10% bandwidth (3.3 GHz) and a tunability range of 2 GHz over bias voltages 0 to 10 V. Theoretical and experimental responses of the filter are in good agreement. The insertion loss of the filter is about 4.5 dB, but this is mainly due to the microstrip line to CPW transitions used for measurement of the filter by a probe-station.

Cascaded Coupled Line Filter With Reconfigurable Bandwidths Using LCP Multilayer Circuit Technology

Abstract: This paper presents a new design method for reconfigurable coupled line filters. The main aim is to develop an analytical design procedure for designing this type of reconfigurable filter with any orders and bandwidths. The new design procedure allows not only making the design easy, but also increasing the passband performance by eliminating the impedance transformers needed for matching purposes used in previous filters. A reconfigurable bandpass filter of this type is designed that can switch between three distinct bandwidth states ranging from around 26% to 50% ripple fractional bandwidth (FBW) centered at 2 GHz. In addition, liquid crystal polymer (LCP) multilayer circuit technology, which offers a great flexibility in realizing required even- and odd-mode impedances for a wideband coupled line filter, is deployed to implement the designed filter. The reconfigurable filter exhibits insertion losses ranging from 0.57 dB for the widest passband state to 1.95 dB for the narrowest passband state. The fabricated filter shows good agreement with EM simulated results.

Compact Filter Configurations Using Concentric Microstrip Open-Loop Resonators

Abstract: This paper presents two highly compact filter configurations using concentric open-loop resonators. A description of each filter configuration is presented, where a linkage between structural features and coupling coefficients is outlined. A third order trisection and a fourth order source-load coupled filter were designed and fabricated at 1.0 GHz, and each filter was shown to occupy an area of just 18 by 18 mm. The measured insertion loss of the third and fourth order filters was 0.83 and 1.20 dB, respectively. Moreover, these structures may also be cascaded to produce higher order compact filters.

A Three-Pole 1.2–2.6-GHz RF MEMS Tunable Notch Filter With 40-dB Rejection and Bandwidth Control

Abstract: This paper presents a high-performance three-pole tunable notch filter with frequency and bandwidth control. The filter is implemented using suspended-stripline resonators and planar 3-bit RF MEMS capacitive networks. A tuning range of 1.1-2.7 GHz with a 40-dB rejection bandwidth of 115±25 MHz is demonstrated with a passband insertion loss <; 0.8 dB. A 40-dB rejection bandwidth of 26-126 and 24-200 MHz is demonstrated at 1.6 and 2.0 GHz, respectively. The filter introduces no noticeable distortion of wideband code-division multiple-access (WCDMA) waveforms with a power of 25 dBm at frequencies corresponding to the 30-40 dB nulls and at the - 3-dB and - 6-dB passband frequencies. At the - 0.5-dB passband frequency, the filter can handle up to 30 dBm of WCDMA power with no measurable distortion. To our knowledge, this filter represents state-of-the-art tuning performance and power handling for planar notch filter designs. The application areas are in wideband cognitive radios with high interference levels.

Analysis of the design space of single-stage and two-stage LC output filters of switched-mode AC power sources

Abstract: This paper proposes a systematic approach to design the output filter of a 10 kW, low-voltage 400 V ll,rms , fouroutput phase, hard-switched AC source based on the Three-Level Neutral Point Clamped Voltage Source Converter topology. Given specifications of the AC source, such as the voltage quality, the control performance or the conducted EMI at the output of the source, are translated into corresponding families of curves in the parameter space of the output filter. The area/volume enclosed by these curves represents the design space of the output filter in which all tuples (L f , C f ), e.g. for a single-stage LC-filter, fulfill every single AC source specification. From all possible filter parameters in the design space, the set of parameters resulting in the smallest filter volume, the lowest filter weight, the highest filter efficiency and/or the lowest filter costs can be selected.

A 0.55V 61dB-SNR 67dB-SFDR 7MHz 4 th -order Butterworth filter using ring-oscillator-based integrators in 90nm CMOS

Abstract: Integrators are key building blocks in many analog signal processing circuits and systems. They are typically implemented using either an opamp-RC or a G m -C architecture depending on bandwidth and linearity requirements. The performance of both these topologies depends on the operational transconductance amplifier (OTA) used to implement the integrator. Reduced supply voltage and lower transistor output impedance make it difficult to implement high-gain wide-bandwidth OTAs in a power-efficient manner. Consequently, the DC gain of the integrator is often severely limited when designed in deep-submicron CMOS processes. Conventional integrators employ multi-stage OTAs operating in weak inversion and forward body biasing to achieve large DC gain at low supply voltages [1]. These techniques require automatic biasing to guarantee robust operation under all conditions and the use of frequency compensation combined with large dimensions needed to bias the transistors in weak inversion severely limits the bandwidth and increases power dissipation. In this paper, we propose a ring-oscillator-based integrator (ROI) that seeks to overcome the limitations of conventional OTA-based integrators.

Third order integrable UHF bandpass filter using active inductors

Abstract: In this article, an UHF third order bandpass filter based on an high-Q active inductor (AI) is described and measurement results, performed on a prototype board, are presented and compared with software simulations. The designed AI includes a passive variable phase- and amplitude-compensating network and a highly linear inverting amplifier, forming a gyrator-C architecture that gives to the filter also frequency and amplitude tuneability proprieties. The fabricated Butterworth filter has a center frequency of 600 MHz and a measured noise figure of 11 dB with a 5 dBm 1-dB compression point and a 82 dB dynamic range. All passive components values have been chosen to allow the circuit to be completely integrated in a standard IC design. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:1426–1429, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26857

A micromechanical bandpass filter with adjustable bandwidth and bidirectional control of centre frequency

Abstract: This paper introduces a tunable, narrow-band, micromechanical filter whose bandwidth and centre frequency can be adjusted independently. The filter is made of two micro-resonators that are electrostatically coupled using a middle electrode. A low coupling strength results in nearly constant bandwidth while one tunes the centre frequency bi-directionally by applying a DC voltage to the coupling electrode. On the other hand, the bandwidth of the filter is independently modified by applying axial stress to one of the resonators, without affecting the signal attenuation through the filter. Analytic and numerical models for the behaviour of the filter are also presented. Test devices with a centre frequency of about 300 kHz were fabricated in a standard micromachining process. Experimental results support the design principle and validity of the proposed models.

EMI filter design: Part III: Selection of filter topology for optimal performance

Abstract: In the first two parts of the electromagnetic interference (EMI) filter design series, the conducted EMI generation mechanism and the method on the measurement of noise source impedances of a switched-mode power supply were described. In this final part, the selection of filter topology for optimal performance is explained. With good accuracy of both amplitude and phase of termination impedances, an EMI filter can be designed systematically to give optimal performance.

Adaptive cosite arbitration system

Abstract: A system for coupling a communication unit to an antenna. The system includes a tunable bandpass filter and a second tunable filter, such as a tunable low-pass filter, in parallel with the tunable bandpass filter. The system also includes a measurement and control unit configured to measure a frequency of a signal generated by the communication unit and to tune the tunable bandpass filter to pass the signal generated by the control unit.

Current-Processing Current-Controlled Universal Biquad Filter

Abstract: This paper presents a current-processing cur- rent-controlled universal biquad filter. The proposed filter employs only two current controlled current conveyor transconductance amplifiers (CCCCTAs) and two grounded capacitors. The proposed configuration can be used either as a single input three outputs (SITO) or as three inputs single output (TISO) filter. The circuit realizes all five different standard filter functions i.e. low-pass (LP), band-pass (BP), high-pass (HP), band-reject (BR) and all-pass (AP). The circuit enjoys electronic control of quality factor through the single bias current without dis- turbing pole frequency. Effects of non-idealities are also discussed. The circuit exhibits low active and passive sen- sitivity figures. The validity of proposed filter is verified through computer simulations using PSPICE.

Parameter selection guidelines for a parabolic sliding mode filter based on frequency and time domain characteristics

Abstract: This paper presents the results of quantitative performance evaluation of an authors' new parabolic sliding mode filter, which is for removing noise from signals in robotics and mechatronics applications, based on the frequency and time domain characteristics. Based on the evaluation results, the paper presents selection guidelines of two parameters of the filter. The evaluation results show that, in the frequency domain, the noise removing capability of the filter is almost the same as that of the second-order Butterworth low-pass filter (2-LPF), but its phase lag is smaller (maximum 150 degree) than that of 2-LPF (maximum 180 degree). Moreover, the filter produces smaller phase lag than a conventional parabolic sliding mode filter with appropriate selection of the parameters. In the time domain, the filter produces smaller overshoot than 2-LPF and the conventional one, while maintaining short transient time, by using an appropriately selected parameter. The presented parameter selection guidelines state that the values of the parameters should be chosen according to some estimated characteristics of the input and some desired characteristics of the output. The effectiveness of the filter and the presented guidelines is validated through numerical examples and their application to a closed-loop, force control of a robot manipulator.

Improving EMI filter design with in circuit impedance mismatching

Abstract: This paper discussed improving EMI design based on propagation path impedance. The way conventionally used in EMI filter design barely includes information on propagation path impedances, although this information is well known as important to filter topology selection and its in-circuit attenuation; besides, filters attenuation is usually measured by small signal insertion gain, which is different from real in-circuit attenuation. This paper starts from the propagation path impedance characterization, and then it investigates into the impacts of the propagation path impedance on the in-circuit filter attenuation. Parasitic effects of the filter are included in the analysis. Parasitics creates multiply resonances and anti-resonances in the propagation path, which can be reflected in filter in-circuit attenuation. By accurate control and design of these parasitic, we can take the advantage of parasitics to improve the filter performance. Furthermore, knowing the relationship between filter impedances and propagation path gives better understanding of how to design an effective filter for noise reduction.

The impact of digital filtering to ECG analysis: Butterworth filter application

Abstract: ECG is a prime important signal for coronary heart diseases which focuses on electrophysiology of heart. Quality diagnosis of ECG is a technological challenge. In high quality diagnostic analysis of the bio-potential signals such as ECG, power line interference (PLI) sometimes referred to as ac pickup or hum is a common problem in recording situation. Especially if computer interpretations of the recorded signals is required, then it is essential that line interference is reduced to minimum so that critical points of ECG waveforms may be accurately determined. By employing an digital filter approach to the problem we can effectively eliminate the causes of interference and avoid drastic remedies such as changing recording sites or installation of expensive shielding. Various possibilities for line interference have been studied and models of digital filter implementation have been constructed. For meaningful and accurate detection, steps have to be taken to discard all noise sources generally termed as filtering of ECG. In this paper an effort is made to develop a Butterworth filter with an effective computerized solution for improving the ECG signal and reducing the interferences associated to it.

Novel Adaptive IIR Filter for Frequency Estimation and Tracking

Abstract: In many applications, a sinusoidal signal may be subjected to nonlinear effects in which possible harmonic frequency components are generated. In such an environment, we may want to estimate (track) the signal's fundamental frequency as well as any harmonic frequencies. Using a secondorder notch filter to estimate fundamental and harmonic frequencies is insufficient since it only accommodates one frequency component. On the other hand, applying a higher-order infinite impulse response (IIR) notch filter may not be efficient due to adopting multiple adaptive filter coefficients. In this article, we present a novel adaptive harmonic IIR notch filter with a single adaptive coefficient to efficiently perform frequency estimation and tracking in a harmonic frequency environment. Furthermore, we devise a simple scheme to select the initial filter coefficient to insure algorithm convergence to its global minimum error.