Showing papers on "Band-stop filter published in 2012"

Addressing DC Component in PLL and Notch Filter Algorithms

Abstract: This paper presents a method for addressing the dc component in the input signal of the phase-locked loop (PLL) and notch filter algorithms applied to filtering and synchronization applications. The dc component may be intrinsically present in the input signal or may be generated due to temporary system faults or due to the structure and limitations of the measurement/conversion processes. Such a component creates low-frequency oscillations in the loop that cannot be removed using filters because such filters will significantly degrade the dynamic response of the system. The proposed method is based on adding a new loop inside the PLL structure. It is structurally simple and, unlike an existing method discussed in this paper, does not compromise the high-frequency filtering level of the concerned algorithm. The method is formulated for three-phase and single-phase systems, its design aspects are discussed, and simulations/experimental results are presented.

1 € filter: a simple speed-based low-pass filter for noisy input in interactive systems

Abstract: The 1 € filter ("one Euro filter") is a simple algorithm to filter noisy signals for high precision and responsiveness. It uses a first order low-pass filter with an adaptive cutoff frequency: at low speeds, a low cutoff stabilizes the signal by reducing jitter, but as speed increases, the cutoff is increased to reduce lag. The algorithm is easy to implement, uses very few resources, and with two easily understood parameters, it is easy to tune. In a comparison with other filters, the 1 € filter has less lag using a reference amount of jitter reduction.

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.

RF Tunable Bandstop Filters With Constant Bandwidth Based on a Doublet Configuration

Abstract: This paper presents a novel approach to design RF tunable bandstop filters with constant absolute bandwidth. The filters are based on a doublet configuration which is attractive for high-order filter designs. In the doublet, two varactor-tuned resonators, arranged in a mirror-symmetrical manner, are coupled to a main transmission line. A novel coupling scheme is utilized between the resonators and the main line. Theoretical analysis indicates that, as the resonant frequency varies, the coupling coefficient within the fixed coupling region can be inherently changed to desirable values to meet the requirement of constant absolute bandwidth. Using the coupling scheme, constant absolute bandwidth can be obtained without extra circuits to control the coupling strengths. For demonstration, first-order and high-order filters are designed. Comparisons of experimental and simulated results are presented to verify the theoretical predications.

Compact Differential Ultra-Wideband Bandpass Filter With Common-Mode Suppression

Abstract: A compact differential ultra-wideband (UWB) bandpass filter (BPF) with planar structure is presented. The circuit of the proposed filter is analyzed, showing that the differential-mode circuit, which consists of two short-ended stubs and an open-ended parallel-coupled lines, performs as a UWB BPF. While the common-mode circuit performs as a UWB bandstop filter, and the common-mode responses are suppressed across the whole UWB differential passband. A microstrip differential UWB BPF is designed, simulated and measured. Simulated and measured results show that the proposed filter has compact size (0.35λg×0.7λg), UWB differential passband (3 dB fractional bandwidth 119%) and UWB common-mode suppression (-10 db attenuation across 2.6-12 GHz).

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.

Ultrawide Tunable Microwave Photonic Notch Filter Based on Stimulated Brillouin Scattering

Abstract: A new ultrawide tunable microwave photonic notch filter that exhibits a very high resolution is presented. It is based on a stimulated Brillouin scattering technique, which processes the modulation sidebands generated by a dual-drive Mach-Zehnder modulator. Tuning is realized by changing the drive frequency to an electro-optic intensity modulator. Experimental results demonstrate a high-resolution notch filter with a 3-dB bandwidth of 82 MHz, a notch depth of over 40 dB, a flat passband from near DC to 20 GHz with very low ripples, and a notch frequency that can be continuously tuned with shape invariance over an ultrawide frequency range from 2 to 20 GHz.

Mechanical vibration reduction control of two-mass permanent magnet synchronous motor using adaptive notch filter with fast Fourier transform analysis

Abstract: A servo drive system with a permanent magnet synchronous motor (PMSM), ball-screw, gear and timing-belt is widely used in industrial applications such as numerical control (NC) machine, machine tool, robot and factory automation. These systems have torsional vibration in the torque transmission from the motor to the mechanical load owing to the mechanical couplings. This vibration reduces the dynamics of the speed responses and may result in damage to the mechanical plant. This study presents an adaptive notch filter with automatic searching of the resonant frequency and bandwidth from the speed error without any mechanical signal feedback to reject the mechanical vibration of the linear feeder system. The proposed control scheme can suppress the torque command signal of a PMSM in the resonant frequency area to reject the mechanical torsional vibration. Since the resonant frequency can be varied by the mechanical configurations and load conditions, the adaptive notch filter is designed to search the vibration frequency automatically and consequently suppress the mechanical resonant vibration. Experimental results show the verification of the proposed adaptive notch filter in a linear feeder system.

Switchable and Tunable Microwave Photonic Brillouin-Based Filter

Abstract: A new structure that realizes a switchable microwave photonic filter, which can be readily switched between a bandpass filter and a notch filter, is presented. It is based on optical processing the sidebands of the RF-modulated signal that is obtained after a dual-drive Mach–Zehnder modulator (DDMZM), using stimulated Brillouin scattering (SBS) effects. Switching of the filter function is simply and conveniently obtained by changing the dc bias to the DDMZM. In addition, the center frequency of the switchable filter can be tuned over a wide frequency range. A detailed analysis and simulation of the DDMZM operation in conjunction with the SBS technique is presented in order to obtain the required optimum bias conditions for the DDMZM for realizing the switching action between the single-bandpass filter and the notch filter and also to select the optimum pump power for the SBS operation. Experimental results demonstrate the ability of this structure to switch between a high-resolution bandpass filter and a high-resolution notch filter, with Q values around 400–500, and the ability to operate over a frequency range of 2–20 GHz.

Craziness based Particle Swarm Optimization algorithm for FIR band stop filter design

Abstract: In this paper, an improved particle swarm optimization technique called Craziness based Particle Swarm Optimization (CRPSO) is proposed and employed for digital finite impulse response (FIR) band stop filter design The design of FIR filter is generally nonlinear and multimodal Hence gradient based classical optimization methods are not suitable for digital filter design due to sub-optimality problem So, global optimization techniques are required to avoid local minima problem Several heuristic approaches are available in the literatures The Particle Swarm Optimization (PSO) algorithm is a heuristic approach with two main advantages: it has fast convergence, and it uses only a few control parameters But the performance of PSO depends on its parameters and may be influenced by premature convergence and stagnation problem To overcome these problems the PSO algorithm has been modified in this paper and is used for FIR filter design In birds' flocking or fish schooling, a bird or a fish often changes directions suddenly This is described by using a “craziness” factor and is modelled in the technique by using a craziness variable A craziness operator is introduced in the proposed technique to ensure that the particle would have a predefined craziness probability to maintain the diversity of the particles The algorithm's performance is studied with the comparison of real coded genetic algorithm (RGA), conventional PSO, comprehensive learning particle swarm optimization (CLPSO) and Parks and McClellan (PM) Algorithm The simulation results show that the CRPSO is superior or comparable to the other algorithms for the employed examples and can be efficiently used for FIR filter design

Intrinsically Switched Varactor-Tuned Filters and Filter Banks

Abstract: Intrinsically switched tunable filters are switched on and off using the tuning elements that tune their center frequencies and/or bandwidths, without requiring an increase in the tuning range of the tuning elements. Because external RF switches are not needed, substantial improvements in insertion loss, linearity, dc power consumption, control complexity, size, and weight are possible compared to conventional approaches. An intrinsically switched varactor-tuned bandstop filter and bandpass filter bank are demonstrated here for the first time. The intrinsically switched bandstop filter prototype has a second-order notch response with more than 50 dB of rejection continuously tunable from 665 to 1000 MHz (50%) with negligible passband ripple in the intrinsic off state. The intrinsically switched tunable bandpass filter bank prototype, comprised of three third-order bandpass filters, has a constant 50-MHz bandwidth response continuously tunable from 740 to 1644 MHz (122%) with less than 5 dB of passband insertion loss and more than 40 dB of isolation between bands.

Tunable notch filtering in multi-transmit applications

Abstract: A radio frequency (RF) communication device comprises a first signal propagating circuit and a second signal propagating circuit, which together enables simultaneous transmission. The first signal propagating circuit is configured with a first tunable notch filter within a first transmit path and the second signal propagating circuit is configured with a second tunable notch filter within a second transmit path. A controller is communicatively coupled to a respective first tuning component and second tuning component of the tunable notch filters. The controller selectively tunes at least one of the tunable notch filters during signal propagation to produce a specific combined notch filtering response that reduces a level of IMD on at least one receive carrier frequency of at least one propagating signal. Aspects of the disclosure also provide a method for making the communication device.

A Pressure Responsive Fluidic Microstrip Open Stub Resonator Using a Liquid Metal Alloy

Abstract: This letter describes a fluidic microstrip bandstop filter with transmission properties that change in discrete states. The filter consists of a liquid metal alloy - eutectic gallium indium (EGaIn) - as the conductive component in microfluidic channels. The fluidity of EGaIn allows the open stub resonator of the filter to change its length by flowing in response to an applied pressure. A series of posts in the channel defines the length of the stub filled by the metal and dictates the pressure needed for the liquid metal to flow and thereby extend the stub length. The frequency response of the filter changes in response to the changes in the length of the resonator stub. This approach is a simple method for creating tunable filters and impedance matching sections using soft materials that change dimensions in response to pressure.

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.

Miniaturized UWB Filters Integrated With Tunable Notch Filters Using a Silicon-Based Integrated Passive Device Technology

Abstract: This paper reports on the implementation of miniaturized ultra-wideband filters integrated with tunable notch filters using a silicon-based integrated passive device technology An ultra-wideband bandpass filter is realized on a micromachined silicon substrate, showing an insertion loss of 11 dB, return loss of better than 15 dB, and attenuation of more than 30 dB at both lower and upper stop-bands, with a spurious-free response up to 40 GHz The filter occupies only 29 mm 24 mm of die area To address the in-band interference issues associated with ultra-wideband communication, very compact tunable notch filters are monolithically integrated with the bandpass filters A two-pole tunable notch filter integrated with an ultra-wideband filter provides more than 20 dB rejection in the 5-6 GHz range to reject U-NII interferences, with a total footprint of 48 mm 29 mm The power handling, linearity, and temperature stability of filters are characterized and presented in this paper

Hands on steering wheel detect in lane centering operation

Abstract: A control system to determine a hands on wheel (HOW) condition is provided. The control system includes a sensor (50) that monitors an amount of applied torque exerted upon a hand wheel (34), and a control module (60) for monitoring the sensor. The control module includes a notch filter to attenuate a normal column mode frequency from the amount of applied torque to produce a filtered torque signal. The normal column mode frequency represents a range of vibrational modes of the hand wheel based on a hands off wheel condition. The control module includes a state detector to receive the filtered torque signal from the notch filter. The state detector determines if the HOW condition exists based on if the filtered torque signal exceeds an ON threshold torque value.

High-repetition-rate single-photon receiver and method therefor

Abstract: A single-photon receiver and method for detecting a single-photon are presented. The receiver comprises a SPAD that receives a gating signal having a fundamental frequency in the 100 MHz to multiple GHz range. The receiver further comprises a two-stage frequency filter for filtering the output of the SPAD, wherein the filter has: (1) a notch filter response at the fundamental frequency; and (2) a low-pass filter response whose cutoff frequency is less than the first harmonic of the fundamental frequency. As a result, the frequency filter removes substantially all the frequency components in the SPAD output without significant degradation of the signal quality but with reduced complexity, cost, and footprint requirement relative to receivers in the prior art.

Tunable Frequency-Quadrupling Dual-Loop Optoelectronic Oscillator

Abstract: A tunable frequency-quadrupling dual-loop optoelectronic oscillator (OEO) based on a polarization modulator is proposed and demonstrated. The introduce of frequency quadrupling in the proposed OEO not only increases the maximal achievable frequency by four times, extends the tuning range by four times, but also enables powerful optical signal processing functions. By incorporating an electrical-tunable yttrium-iron-garnet bandpass filter in the proposed OEO and employing a fiber Bragg grating as a wavelength-fixed optical notch filter, a high-quality microwave signal with a frequency tunable from 32 to 42.7 GHz is generated. The phase noise of the generated frequency-quadrupling signal is also studied.

Method and system for obtaining an audio signal

Abstract: A method and system for obtaining an audio signal. In one embodiment, the method comprises receiving a first sound signal at a first microphone arranged at a first height vertically above a substantially flat surface; receiving a second sound signal at a second microphone arranged at a second height vertically above the substantially flat surface; processing a signal provided by the first microphone using a low pass filter; processing a signal provided by the second microphone using a high pass filter; adding the signals processed by the low pass filter and the high pass filter to form a sum signal; and outputting the sum signal as an audio signal.

Electrically Tunable Terahertz Notch Filters

Abstract: In this letter we present a switchable THz notch filter. The filter contains a liquid crystal layer that acts as a half wave retarder in one state and as an isotropic layer in the other state. The device combines three unique properties: it can be switched electrically, it provides a filter depth of 35 dB at 350 GHz and it can be tuned over wide frequency range from 350 GHz to 700 GHz.

Compact UWB Bandpass Filter With Dual Notch Bands Using Open Circuited Stubs

Abstract: In this letter, an ultra-wideband (UWB) bandpasss filter with multiple notch bands is presented. The UWB bandpass characteristic is achieved using a modified distributed highpass filter (HPF) and suppressing higher order harmonics of the HPF by realizing defected stepped impedance resonator. The dual band notches at 5.75 and 8.05 GHz are obtained by embedding two open stubs on the main microstrip line. The in band and out of band performance obtained from fullwave electromagnetic simulation, equivalent circuit model and measurement are in good agreement.

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.

8-Path tunable RF notch filters for blocker suppression

Abstract: The huge growth of the number of wireless devices makes wireless coexistence an increasingly relevant issue. If radios operate in close proximity, blockers as strong as 0dBm may occur, driving almost any receiver in compression (note that 0dBm in 50Ω corresponds to a peak-to-peak voltage of half a 1.2V supply). Thus RF blocker filtering is highly wanted. However, fixed filters are undesired when aiming for multiband, software-defined or cognitive radio transceivers. Passive LC filters show limited Q and tunability. Recently frequency translated filtering has been proposed as a potential solution direction for high-Q filtering [1–5]. In [1,2] we showed that by applying the “N-path concept” [6], more than a decade of center frequency range with good linearity, compression point (P 1dB >0dBm, IIP3 >14dBm) and low noise is feasible for a bandpass (BP) filter. In [3] a notch filter with a combination of active and passive mixers is applied in a feedforward path realizing a BP filter. Moreover in [5] the low input impedance of a transimpedance amplifier with feedback is upconverted to create a notch filter at low frequencies (80MHz) suppressing TX leakage in an FDD system. In this work we explore the possibility to realize a notch filter applying the N-path concept at RF frequencies and in a completely passive way. A single-ended (SE) and a differential 8-path notch filter with passive frequency mixing are presented. The filters are power-matched in the input and output in the passband and provide a low insertion loss, high compression point and also low noise property, thus they can be utilized in front of a receiver to provide rejection of high-power blockers with a large frequency tuning range.

Second-order filter with notch for use in receivers to effectively suppress the transmitter blockers

Abstract: The disclosed invention relates to a transceiver system comprising a notch filter element configured to suppress transmitter blockers (i.e., transmitter interferer signals) within a reception path. In some embodiments, the transceiver front-end comprises a differential reception path, having a first differential branch and a second differential branch, configured to provide an RF differential input signal having a transmitter blocker to a transimpedance amplifier, comprising a first-order active filter and a notch filter element. The notch filter element comprises a stop band corresponding to a frequency of a transmitted signal, such that the notch filter element suppresses the transmitted blocker without degrading the signal quality of the received differential input signal.

Prevention of ANC instability in the presence of low frequency noise

Abstract: An active noise control (ANC) processor has an adaptive filter that uses a reference signal to produce an anti-noise signal, and an error signal to evaluate cancellation performance. An adaptive filter algorithm engine configures the filter coefficients of the adaptive filter, in accordance with pre-shaped versions of the error and reference signals. The pre-shaping filter has a high-pass transfer function and enables the adaptive algorithm engine to increase noise cancellation performance in a high frequency band during the presence of focused or narrow-band noise energy in a low frequency band. Other embodiments are also described and claimed.

Study of a T-Shaped Slot With a Capacitor for High Isolation Between MIMO Antennas

Abstract: In this letter, an isolation improvement method between two closely packed planar inverted-F antennas (PIFAs) is proposed via a miniaturized ground slot with a chip capacitor. The proposed T-shaped ground slot acts as a notch filter, and the capacitor is utilized to reduce the slot length. The equivalent circuit model of the proposed slot with the capacitor is derived. The measured isolation between two PIFAs is down to below -20 dB at the whole WLAN band of 2.4 GHz.

Compact Wideband Bandstop Filter With Five Transmission Zeros

Abstract: A compact parallel-coupled transmission line section, connected at their both ends, is presented to obtain multiple transmission zeros. As much as five transmission zeros can be obtained. The zeros can be arranged to design a sharp rejection wideband bandstop filter (BSF). A lossless transmission line model is used to analyze the structure and hence to obtain closed form expressions for the -parameters and design graphs to facilitate the filter synthesis procedure. Theoretical predictions are validated by fabricating a BSF in microstrip line technology. The single filter unit provides 29 dB stopband over a fractional bandwidth of 60% at the mid-band frequency of 1.47 GHz.

Extended Passband Bandstop Filter Cascade With Continuous 0.85–6.6-GHz Coverage

Abstract: This paper presents a cascade of tunable bandstop filters with a wide spurious-free upper passband, which is completely spanned by the tuning range of the notch responses. A collection of resonators is shown to be able to provide bandstop filter responses over a 7.8 to 1 tuning range. By using spurious-free upper passband aperture-coupled cavity bandstop filters, multiple resonators, each with octave tuning, can cover a multioctave frequency range in a cascade. It is shown that the upper passband of this type of filter is limited by the reactance of the coupling apertures, which produce an unwanted in-band resonance unless designed properly. The details of this design process are explained and used to design a six-resonator bandstop filter cascade that is able to provide a bandstop filter response with up to 55 dB attenuation over the continuous band of 0.85-6.6 GHz. Through dynamic allocation of the cascade circuit's transmission zeros, one-, two-, three-, and four-pole bandstop filter responses of variable bandwidth can be realized over different frequency ranges, offering numerous bandwidth-attenuation level tradeoff combinations.