Showing papers on "Band-stop filter published in 2009"

A Novel Wideband Common-Mode Suppression Filter for Gigahertz Differential Signals Using Coupled Patterned Ground Structure

Abstract: A wideband and compact filter design for common-mode noise suppression in high-speed differential signals is proposed based on two U-shaped and one H-shaped coupled patterned ground structure. An equivalent model of three coupled LC resonators to predict the common-mode suppression characteristics is also developed with good agreement to the full-wave simulation and measurement result. A test sample is designed and fabricated on a standard printed circuit board (PCB). It is found the common-mode noise can be reduced by the filter over 15 dB from 3.6 to 9.1 GHz and over 75% of amplitude in the time domain. More important, the differential signal integrity, in terms of insertion loss and group delay in the frequency domain and eye diagrams in the time domain, is not degraded within the wide bandwidth. The fractional bandwidth of the stopband can reach 87% and the filter size is about 0.44 lambdag times 0.44 lambdag. The radiation caused by the common-mode current on the attached I/O cables is also efficiently suppressed by 10 dB on average within the designed stopband. To our best knowledge, it is the first low-cost common-mode filter designed for the gigahertz high-speed signals with the largest fractional bandwidth and most compact size on a PCB.

On the generalization of second-order filters to the fractional-order domain

Abstract: This work is aimed at generalizing the design of continuous-time second-order filters to the non-integer-order (fractional-order) domain. In particular, we consider here the case where a filter is constructed using two fractional-order capacitors both of the same order α. A fractional-order capacitor is one whose impedance is Zc = 1/C(jω)α, C is the capacitance and α (0 < α ≤ 1) is its order. We generalize the design equations for low-pass, high-pass, band-pass, all-pass and notch filters with stability constraints considered. Several practical active filter design examples are then illustrated supported with numerical and PSpice simulations. Further, we show for the first time experimental results using the fractional capacitive probe described in Ref. 1.

Current Harmonic Compensation by a Single-Phase Shunt Active Power Filter Controlled by Adaptive Neural Filtering

Abstract: This paper presents a single-phase shunt active power filter (APF) for current harmonic compensation based on neural filtering. The shunt active filter, realized by a current-controlled inverter, has been used to compensate a nonlinear current load by receiving its reference from a neural adaptive notch filter. This is a recursive notch filter for the fundamental grid frequency (50 Hz) and is based on the use of a linear adaptive neuron (ADALINE). The filter's parameters are made adaptive with respect to the grid frequency fluctuations. A phase-locked loop system is used to extract the fundamental component from the coupling point voltage and to estimate the actual grid frequency. The current control of the inverter has been performed by a multiresonant controller. The estimated grid frequency is fed to the neural adaptive filter and to the multiresonant controller. In this way, the inverter creates a current equal in amplitude and opposite in sign to the load harmonic current, thus producing an almost sinusoidal grid current. An automatic tuning of the multiresonant controller is implemented, which recognizes the largest three harmonics of the load current to be compensated by the APF. The stability analysis of the proposed control system is shown. The methodology has been applied in numerical simulations and experimentally to a properly devised test setup, also in comparison with the classic sinusoidal current control based on the P-Q theory.

Demonstration of a Tunable Microwave-Photonic Notch Filter Using Low-Loss Silicon Ring Resonators

Abstract: We present a fully tunable multistage narrowband optical pole-zero notch filter that is fabricated in a silicon complementary metal oxide semiconductor (CMOS) foundry. The filter allows for the reconfigurable and independent tuning of the center frequency, null depth, and bandwidth for one or more notches simultaneously. It is constructed using a Mach-Zehnder interferometer (MZI) with cascaded tunable all-pass filter (APF) ring resonators in its arms. Measured filter nulling response exhibits ultranarrow notch 3 dB BW of 0.6350 GHz, and nulling depth of 33 dB. This filter is compact and integrated in an area of 1.75 mm2. Using this device, a novel method to cancel undesired bands of 3 dB bandwidth of < 910 MHz in microwave-photonic systems is demonstrated. The ultranarrow filter response properties have been realized based on our developed low-propagation loss silicon channel waveguide and tunable ring-resonator designs. Experimentally, they yielded a loss of 0.25 dB/cm and 0.18 dB/round trip, respectively.

Quadruple-Mode UWB Bandpass Filter With Improved Out-of-Band Rejection

Abstract: A quadruple-mode ultra-wideband (UWB) bandpass filter with sharp out-of-band rejection is presented in this work. As a starting part of designing a quadruple-mode filter, a mode graph of the initial triple-mode resonator is studied to choose its proper dimensions. Based on these pre-determined dimensions of this triple-mode resonator, two short-circuited stubs are introduced in this resonator to generate two transmission zeros near the lower and upper cut-off frequencies, leading to a higher rejection skirt outside the desired passband. Moreover, as these two stubs are installed, the fourth resonant mode falls down and works together with the first three resonant modes to form a novel quadruple-mode UWB filter. Finally, a filter prototype is designed and fabricated to experimentally validate the attractive in-band and out-of-band performances as predicted in theory.

Reconfigurable planar filters

Abstract: Electronically reconfigurable or tunable microwave filters are attracting more attention for research and development because of their increasing importance in improving the capability of current and future wireless systems. For instance, emerging ultrawideband (UWB) technology requires the use of a wide radio spectrum. However, the frequency spectrum as a resource is valuable and limited, so the spectrum is always being used for several purposes, which means it is full of unwanted signals when an operation such as a UWB wireless system is concerned. In this case, existing undesired narrowband radio signals, which vary from place to place and from time to time, may interfere with the UWB system's range. A solution for this is to introduce an electronically switchable or tunable narrow rejection band (notch) within the passband of a UWB bandpass filter. Such an electronically reconfigurable filter is also desired for wideband radar or electronic warfare systems. This paper discusses the development of electronically reconfigurable filter types.

Compact microstrip lowpass filter with sharp roll-off and wide stop-band

Abstract: A microstrip lowpass filter with enhanced performance is developed. The studied filter is based on a novel patch resonator that features strong slow-wave effects, and can also implement either an improved roll-off or an enhanced stop-band. A demonstrator filter with 3 dB cutoff frequency fc =2.4=GHz is optimally designed, fabricated and measured. Results indicate that a roll-off of 92.5=dB/GHz together with a relative stop-band bandwidth of 135.5= (referred to a 30=dB suppression) is obtained while achieving a highest figure-of-merit of 10106. Both simulations and measurements are presented and compared.

Quiet zone control system

Abstract: An active noise control system generates an anti-noise signal to drive a speaker to produce sound waves to destructively interfere with an undesired sound in a quiet zone. The anti-noise signal is generated with an adaptive filter having filter coefficients. The coefficients of the adaptive filter may be adjusted based on a first filter adjustment from a first listening region, and a second filter adjustment from a second listening region. A first weighting factor may be applied to the first filter adjustment, and a second weighting factor may be applied to the second filter adjustment. The first and second weighting factors may dictate the location and size of the quiet zone as being outside or partially within at least one of the first listening region and the second listening region.

Disk drive calibrating VCM notch filter by increasing the width and/or the depth of the notch

Abstract: A disk drive is disclosed comprising a disk, a head, a voice coil motor (VCM) for actuating the head over the disk, and control circuitry comprising a notch filter for generating a VCM control signal, wherein a notch of the notch filter comprises a frequency, a width, and a depth. The notch filter is calibrated by initializing at least one of the width and the depth of the notch, measuring a quality metric of the notch filter, and increasing at least one of the width and the depth of the notch until the quality metric indicates good performance.

Discrete Frequency Tuning Active Filter for Power System Harmonics

Abstract: Severe voltage distortion, due to power system harmonic resonance, has been reported in recent years. This issue becomes more significant in high penetration of a photovoltaic (PV) network. A conventional voltage detection active filter operates as similar conductance for all harmonic frequencies to resolve this problem whether in a fixed conductance command or in an automatic gain adjustment control. However, its filtering capability is impeded by the mismatch between the active filter and the radial line, and the voltage distortion may still be significant. This paper proposes a discrete frequency tuning active filter to suppress power system harmonics. The active filter operates as variable conductance for each individual harmonic frequency. Each harmonic conductance is dynamically adjusted according to the corresponding harmonic voltage distortion of the active filter installation point in response to increase or decrease of nonlinear loads, or variation of resonant frequency in the power system. The mismatching problem between the feeder impedance and the active filter can be avoided effectively. Therefore, harmonic voltage distortion can be maintained at an allowable level throughout the feeder with lower peak current and lower rms current of the active filter, and loads installed at various locations of the power system receive more uniform voltage waveform.

Analysis and Design of an Integrated Notch Filter for the Rejection of Interference in UWB Systems

Abstract: A 0.13-mu m CMOS fourth-order notch filter for the rejection of the 5-6 GHz interference in UWB front-ends is reported. The filter is integrated into an analog front-end for Mode #1 UWB. A thorough analysis based on a simplified model of the filter is carried out. An algorithm for the automatic tuning and calibration of the filter is also discussed and demonstrated. Two versions of the circuit are designed and fabricated: the first comprises a low-noise amplifier and the filter, and the second expands it to a complete front-end. In the latter version the filter was also redesigned. The filter provides more than 35 dB of attenuation and has a tuning range of 900 MHz, adding less than 30% power consumption to the LNA. The out-of-band IIP3 (higher than -13.2 dBm with the filter off) takes a 9-dB advantage from the filter and the compression of the gain due to the out-of-band blocker is reduced by at least 6 dB in the complete front-end. The conversion gain of the front-end is 25 dB per channel, its average noise figure is lower than 6.2 dB, and its in-band 1-dB compression point is higher than - 30 dBm at a power consumption of 32 mW.

Ultra-Wideband Bandpass Filter With Multiple Notch Bands Using Nonuniform Periodical Slotted Ground Structure

Abstract: A novel ultra-wideband (UWB) bandpass filter that is capable of integrating multiple notch bands is proposed in this paper. A multilayer nonuniform periodical structure, which can generate multiple transmission zeros, is deployed in the filter design to improve the selectivity and upper stopband performance of the filter. Short-circuited stub resonators are then integrated to obtain multiple notch bands. The compact footprint of the filter is achieved. UWB filters of this type without a notch and with single-, double-, and triple-notch bands are designed to meet the Federal Communications Commission-defined UWB indoor limit. The designed filters are verified by experiments and fabricated by using multilayer liquid-crystal polymer lamination technology. Both full-wave simulated and measured results are presented and good agreement between them is observed. The proposed filter has good performance and is attractive for UWB communication and radar systems.

Compact UWB Bandpass Filter Based on Signal Interference Techniques

Abstract: This letter presents a new type of compact ultra-wideband (UWB) bandpass filter (BPF) based on interference techniques. The structure is formed by a short-ended coupled line coupler connected in parallel to a transmission line. The transmission and reflection zeros of the filter can be controlled through the analytical equations and rules given. To validate the suggested filter scheme, the design, fabrication and measurement of a microstrip UWB BPF is presented.

Widely Tunable Microwave Photonic Notch Filter Based on Slow and Fast Light Effects

Abstract: A continuously tunable microwave photonic notch filter at around 30 GHz is experimentally demonstrated and 100% fractional tuning over 360deg range is achieved without changing the shape of the spectral response. The tuning mechanism is based on the use of slow and fast light effects in semiconductor optical amplifiers assisted by optical filtering.

Microwave photonic filter with single bandpass response

Abstract: A new microwave photonic filter that solves the problem of realising a single bandpass RF response is presented. The filter is based on using phase modulation together with a pair of gratings, and eliminates the baseband response and periodic spectral response of typical FIR filters. Experimental results demonstrate a single passband square-type bandpass filter response, and operation to high frequencies.

Differential-mode ultra-wideband bandpass filter on microstrip line

Abstract: A differential-mode ultra-wideband (UWB) bandpass filter on a microstrip line is proposed and implemented with good common-mode suppression. A sixth-stage branch-line differential-mode bandpass filter is designed with the specified UWB passband. By introducing two pairs of open-circuited stubs in the symmetrical plane, the differential-mode frequency response remains unchanged but its common-mode counterpart is reshaped to achieve the stopband in the overall UWB. A filter is then fabricated for experimental verification of the proposed technique.

Harmonic-Suppressed Bandpass Filter Based on Discriminating Coupling

Abstract: This letter presents a novel method to suppress harmonic responses of parallel-coupled bandpass filters. The harmonic suppression is based on discriminating coupling. The coupling coefficient at fundamental resonant frequency can be tuned to desirable values whereas it is zero at the second harmonic. Hence, the coupling region blocks the second harmonic but still allows the transmission of signals at passband frequency. Benefiting from this feature, the second harmonic can be suppressed without degrading the passband performance. Furthermore, no additional circuit is needed. For demonstration purpose, two example filters are implemented. The experimental results are presented to verify the proposed method.

A Wideband and High Rejection Multimode Bandpass Filter Using Stub Perturbation

Abstract: A novel multimode bandpass filter with high and wide rejection band is proposed by using an open stub. The open-stub has two functions in the filter: (1) perturbation for the multimode operation and (2) zero point generation at the stopband for the stopband control. With proper input/output coupling, additional two poles, i.e., four poles, can be generated for the proposed filter structure. The design is then verified by experiment. The single structure four-mode filter has low insertion loss, good stopband performance, and compact size and linear phase.

Electronically Reconfigurable Microwave Bandpass Filter

Abstract: A new class of reconfigurable bandpass filter based on parallel-coupled switched delay line approach is presented in this paper. The approach allows both center frequency and passband bandwidth to be reconfigured electronically. In contrast to conventional approach, the effects of the switch losses are relatively insignificant and can be treated as an auxiliary effect and therefore the filter has low passband loss. Despite the loss performance, the filter provides excellent linearity performance with large power handling capability. Theoretical analysis is presented and the feasibility of the approach has been experimentally verified with microstrip circuit prototypes. The first filter prototype provides narrowband quasi-elliptic filter response with constant bandwidth (50-MHz) tuning across 45% tuning range. The minimum stopband rejection level is 45 dB. The second filter possesses passband-width 3:1 ratio tunability. The third filter provides both functionalities which allow center frequency and passband bandwidth to be reconfigured. All filters have a 20 dBm and are immune from power saturation effect. The measured results demonstrate improved performance in terms of linear and nonlinear characteristic compared with prior works.

Self-adaptive digital rf bandpass and bandstop filter architecture

Abstract: A system and method provides adaptive digital front end control of an incoming radio frequency (RF) signal to identify RF characteristics in that signal, such as interference or desired data signals and adaptively control digital filter elements to selectively tune only portions of the RF signal to produce a filtered output signal, on a per cycle basis, prior to communicating the RF signal to an underlying wireless communication device, such as a base station in cellular network, cellular phone, wireless router base station, cognitive radio, or other wireless communication device Each digital filter element may be tuned in frequency and bandwidth of operation and collectively the elements form an adaptive filter stage with elements configurable into both bandpass and bandstop filters for cascaded operation

Compact UWB Filter With Double Notch-Bands Using Multilayer LCP Technology

Abstract: A novel ultra wideband (UWB) bandpass filter with double notch-bands is presented in this paper. Multilayer schematic is adopted to achieve compact size. Stepped impedance resonators (SIRs), which can also suppress harmonic response, are designed on top and second layers, respectively, and broadside coupling technique is used to achieve tight couplings for a wide passband. Folded SIRs that can provide desired notch-bands are designed on the third layer and coupled underneath the second layer SIRs. The designed prototype is fabricated using multilayer liquid crystal polymer (LCP) technology. Good agreement between simulated and measured response is observed. The fabricated filter has dual notch-bands with center frequencies of 6.4/8.0 GHz with 3 dB bandwidths of 9.5%/13.4% and high rejection levels up to 26.4 dB and 43.7 dB at 6.4/8.0 GHz are observed, respectively. It also has low-insertion losses and flat group delay in passbands, and excellent stopband rejection level higher than 30.0 dB from 11.4 GHz to 18.0 GHz.

Capacitor and inductor elements physically disposed in series whose lumped parameters are electrically connected in parallel to form a bandstop filter

Abstract: One or more inductors and one or more capacitors are physically disposed relative to one another in series and are electrically connected to one another in parallel to form a bandstop filter. Chip inductors and chip capacitors having spaced apart conductive terminals are physically arranged in end-to-end abutting relation to minimize electrical potential between adjacent conductive terminals. The bandstop filter may be hermetically sealed within a biocompatible container for use with an implantable lead or electrode of a medical device. The values of the inductors and the capacitors are selected such that the bandstop filter is resonant at one or more selected frequencies, such as an MRI pulsed frequency.

A Compact Wideband Microstrip Filter Using Folded Multiple-Mode Resonator

Abstract: A compact wideband microstrip filter using a folded multiple-mode resonator is proposed. The filter contains only one resonator, which operates as not only a resonant element but also an open stub. The filter simultaneously realizes a broad passband, a compact size, and two transmission zeros at both the lower and upper stopbands. The transmission zero mechanism is investigated in detail through the simple transmission line equation. A lucid equivalent circuit is given both for analysis and initial design of the proposed filter. The fabricated filter shows the merits which are listed as follows: compact size and sharp skirts.

Switched capacitor notch filter

Abstract: A switched capacitor notch filter for sampling an input signal using multiple sampling capacitors and multiple non-overlapping time periods. The charge from the sampling capacitors is averaged and transferred to the filter output during another non-overlapping time period.

A Novel Low-Pass Filter With an Embedded Band-Stop Structure for Improved Stop-Band Characteristics

Abstract: This letter presents a novel design of a microstrip low- pass filter (LPF) with an embedded band-stop structure, which is constructed from a simple two transmission line band-stop filter. The band-stop structure is ingeniously embedded into a classical step-impedance microstrip LPF. The stop-band of the proposed LPF is more than two times broader than the original design, while its cut-off frequency remains at 1.8 GHz. The embedded structure does not increase the physical dimension of the LPF, but improves the performance significantly. Measured results agree with simuAcircnot lation well, and validate the dual-frequency design method.

A Dual-Band Bandpass Filter Based on Generalized Negative-Refractive-Index Transmission-Lines

Abstract: A dual-band bandpass filter is presented. The filter is composed of generalized negative-refractive-index transmission-lines (NRI-TL) realized in microstrip. The filtering mechanism relies on all four of the generalized NRI-TLs' left-handed and right-handed passbands. Under the closed stopband condition, two passbands are achieved. A complete design procedure is described. A fabricated example measures 0.25lambdao0.25lambdao, where omegao is the wavelength of the center frequency of the stopband. Maximum insertion loss in the passbands (centered around 4 GHz) is measured at 1.5 dB.

A 240-MHz Low-Pass Filter With Variable Gain in 65-nm CMOS for a UWB Radio Receiver

Abstract: An integrated fifth-order continuous-time low-pass filter for a WiMedia ultrawideband radio receiver is described in this paper. The prototype filter is realized with a passive pole at the filter input and a fourth-order leapfrog filter in which the gm-C technique with pseudodifferential transconductors is used. The transconductors do not include internal nodes, and they are designed to have a nominal 26-dB dc gain, of which process, voltage, and temperature variations are controlled by means of a negative resistance circuit. The losses of the low-dc-gain filter integrators are already taken into account in the filter synthesis. The passband edge frequency of the implemented filter is 240 MHz in order to receive multiband-orthogonal-frequency-division-multiplexing signals using the direct-conversion topology. The voltage gain of the filter can be controlled from 9 to 43 dB in the 1-dB gain steps. The filter achieves a 7.8-nVradicHz input-referred noise density, a -8-dBV out-of-band third-order intermodulation intercept point, and a +15-dBV out-of-band second-order intermodulation intercept point. The circuit uses a 1.2-V supply and has been fabricated in a modern 65-nm CMOS technology.

Frequency-agile bandstop filter with tunable attenuation

Abstract: A frequency-agile bandstop filter technology with tunable stopband attenuation and constant absolute bandwidth is described. The technology is demonstrated by a six-resonator planar microstrip filter with simultaneous varactor-diode tuning of stopband attenuation from 30dB to 50dB and of operating frequency from 1.8 GHz to 2.2 GHz, with a stopband bandwidth of 60 MHz and absolute 3dB bandwidth of less than 390 MHz.

Millimeter wave notch filters based on ferromagnetic resonance in hexagonal barium ferrites

Abstract: A hexagonal ferrite-based millimeter wave notch filter was demonstrated. The filter consists of an M-type BaFe12O19 (BaM) slab sitting on top of a stripline. The band-stop filtering response originates from the ferromagnetic resonance absorption in the BaM slab. The BaM slab has an in-plane uniaxial anisotropy field of 17 kOe. This anisotropy field facilitates the operation of the filter beyond 50 GHz without a need of high external fields. The operating frequency increases linearly with the external field, while the bandwidth versus field profile shows a U-shaped response. The physical mechanisms for these responses were discussed.