Narrow-band Notch Research Articles

Magnonic notch filter based on spin wave caustic beams

Here, we study a magnonic crystal made of low-damping yttrium iron garnet that utilizes pseudo-caustic spin wave beams generated from subwavelength square well features arranged in a two-dimensional array. The lattice symmetry and the angle between the caustic beam propagation direction and the applied magnetic field were tailored to optimize the interaction of spin waves with the engineered defects. A prominent, narrow 3 MHz feature with large rejection efficiency is observed in the spin wave transmission spectrum that could be useful as a narrowband notch filter, and time- and space-resolved Brillouin light scattering (BLS) measurements suggest that both caustic interference and edge effects may contribute to this notch feature. Furthermore, the BLS measurements show that caustics are generated efficiently at the laser ablated wells, and by tuning the frequency by 30 MHz, the caustic beam angles and, hence, the details of how the spin wave caustics hit the ablated wells change sufficiently to add and remove caustic beams, which can be used to create additional device functionality. The generation and conversion of caustic beams show promise for applications that require directional energy transport and for magnonic devices.

Development of the 174GHz collective Thomson scattering diagnostics at Wendelstein 7-X.

In this paper, we present the design and commissioning results of the upgraded collective Thomson scattering diagnostic at the Wendelstein 7-X stellarator. The diagnostic has a new radiometer designed to operate between the second and third harmonics of the electron cyclotron emission from the plasma at 171-177GHz, where the emission background has a minimum and is of order 10-100eV. It allows us to receive the scattered electromagnetic field with a significantly improved signal-to-noise ratio and extends the set of possible scattering geometries compared to the case of the original instrument operated at 140GHz. The elements of the diagnostic are a narrowband notch filter and a frequency stabilized probing gyrotron that will allow measuring scattered radiation spectra very close to the probing frequency. Here, we characterize the microwave components applied to the radiometer and demonstrate the performance of the complete system that was achieved during the latest experimental campaign, OP2.1.

Notch Microwave Photonic Filter With Narrow Bandwidth and Ultra-High All-Optical Tuning Efficiency Based on a Silicon Nanobeam Cavity

We propose and experimentally demonstrate a narrowband notch microwave photonic filter (MPF) with an ultra-high all-optical tuning efficiency based on an optimized high-quality (Q) nanobeam photonic crystal (PhC) cavity. By optimizing the structural parameters, the hole shapes and the waveguide width of the cavity, a silicon nanobeam cavity with a theoretical high-Q factor of 4×10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">8</sup> , a small mode volume (V) of 0.32(λ/ <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n</i> ) <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> and a compact size of 6 μm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> could be obtained. Due to the extremely high Q/V ratio beyond 1×10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">9</sup> , the nonlinear effects in the cavity could be efficiently excited, which is beneficial for on-chip low-power signal processing. In the experiment, by adjusting the wavelength of the optical carrier, the central frequency of the notch MPF could be widely tuned from 1 GHz to 40 GHz with maintaining the 3dB-bandwidth around 198 MHz and rejection ratios beyond 50 dB. On the other side, the central frequency of the MPF could be all-optically tuned based on the nonlinear effects in the cavity. Owing to the cavity extremely high Q/V ratio, the MPF frequency can be adjusted with an ultra-high tuning efficiency of 308.8 GHz/mW. To the best of our knowledge, whether the notch MPF narrow 3dB-bandwidth of 198 MHz or the all-optical tuning efficiency of 308.8 GHz/mW is a record value among the reported silicon-cavity-based notch MPFs with such a compact device size. With the dominant advantages of sub-gigahertz narrowband, wide tuning range, ultra-high all-optical tuning efficiency and extremely compact cavity size, the proposed MPFs illustrate competitive performance for on-chip microwave signal processing.

Narrow-band notch filter and refractive index sensor based on rectangular-semi-annular cavity coupled with MIM waveguide structure

In this work, a symmetric structure based on a metal-insulator-metal (MIM) waveguide is proposed for narrow-band notch filters and refractive index sensors. The structure comprises a symmetrically intersecting rectangular-semi-annular cavity and a long straight waveguide. The transmission spectrum and magnetic field distribution of the notch filter are studied and analyzed by the finite element method (FEM) with scattering boundary conditions (SBC). Our analysis reveals that the band-stop filter exhibits a minimum transmittance of 0.35%, a bandwidth of 34 nm, and a quality factor (Q) of 35.16. These characteristics include low stop-band transmittance, a narrow bandwidth, and a high Q value. Furthermore, our structure allows for independent adjustment of the narrow band filtering range by varying geometric parameters such as H, d, R1, and d. Additionly, we conduct theoretical analysis to investigate the sensing properties of the structure. The refractive index sensitivity of the structure reaches a high value of 1222 nm RIU−1, accompanied by a figure of merit(FOM*) of up to 175.9. These results demonstrate the structure’s excellent filtering properties and high-sensitivity sensing characteristics.Consequently, it holds significant potential for application in high-density integrated circuits and nano-optics.

Portable diagnostic package for Thomson scattering and optical emission spectroscopy on Princeton field-reversed configuration 2 (PFRC 2).

An Advanced Research Projects Agency-Energy funded diagnostic system has been deployed to the Princeton field-reversed configuration 2 (PFRC-2) device, located at Princeton Plasma Physics Laboratory. The Portable Diagnostic Package (PDP), designed at Oak Ridge National Laboratory, allows for the measurement of Thomson Scattering (TS) for electron density and temperature and Optical Emission Spectroscopy (OES) for ion temperature, impurity density, and ion velocity. A tunable spectrometer on the PDP with three gratings provides the flexibility to measure low (1eV) and high (1000eV) electron temperature ranges from TS. Additionally, using a second spectrometer, the OES diagnostic can survey light emission from various ion excitation levels for wide wavelength ranges. The electron density (<2 × 1019m-3) of plasmas generated in PFRC-2 has been below the PDP TS discrimination threshold, which has made TS signal detection challenging against a high-background of laser stray light. The laser stray light was iteratively reduced by making modifications to the entrance and exit geometry on PFRC-2. Rayleigh scattering experiments on PFRC have yielded the TS discrimination sensitivity to be >1 × 1020m-3 for the PDP. A recently implemented narrow-band notch spectral filter that masks the second harmonic 532nm Nd:YAG laser wavelength has increased the system's TS light discrimination sensitivity 65 times compared to the instance when the notch filter was not implemented. The hardware implementation including design changes to the flight tubes and Brewster windows will be discussed, along with results from Rayleigh and rotational Raman scattering sensitivity analyses, which were used to establish a quantitative figure of merit on the system performance. The Raman scattering calibration with the notch filter has improved the PDP electron density threshold to 1 ± 0.5 × 1018m-3.

Modeling of a compact ultra-wideband bandpass filter with a single notch using DGS and DMS technology

A compact, low loss microstrip ultra-wideband (UWB) bandpass filter (BPF) with a narrow notch band is proposed in this article for using wireless communication applications within the unlicensed UWB range reported by the Federal Communications Commission. A systematic approach is presented to establish the UWB-BPF structure followed by a narrow notch within it. The UWB-BPF response is achieved by integrating a defected structures-based lowpass filter and a short-stepped impedance stub-based highpass filter. The narrow notch band is obtained by embedding two-stepped impedance stubs. The physical dimensions of the stubs can be optimized to select a specific frequency for the notch band. The UWB-BPF structure without the notched band, having a center frequency of 3.69 GHz, provides a fractional bandwidth (FBW) of 157%. The stopband suppression is −26 dB and it is broadened up to 15 GHz. On the other hand, the notched band response is obtained at 5.8 GHz with an FBW of 49.78% which is used for avoiding interference from the wireless local area network. The proposed structures are fabricated and measured for experimental validation.

Design of feedback-structured IIR notch filter with transient suppression using gain variation

In many applications of notch filtering, short transient response and high quality factors are very important issues. Increasing Q factor, decreases the bandwidth and improves magnitude selectivity near the notch frequency, but unfortunately increases the transient duration of the response. Recently, time-variant methods using exponential or sigmoid functions are considered to enhance the notch filter performance. In this paper, conventional and feedback-structured notch filters (following a recent work by Pei et al) are investigated in details. Using feedback structure, anyone can obtain a good narrow-band notch filter by tuning the feedback gain. However, it suffers from a long transient duration. In order to improve the performance of the filter, a new simple time-variant method to control the pole-position is introduced. Proposed method can keep the pole radius in the minimum value to decrease the transient duration more efficiently than other recently-reported ones as Piskorowski, Li and Rana methods. Also, it drives the pole to approach the unit circle or final position rapidly, normally after a few samples, while attaining a narrow bandwidth. In this paper, the performance of the proposed filter is compared with Piskorowski, Li and Rana methods. Simulation results show that the proposed algorithm can improve the performance of the feedback-structured filter compared to other methods. The results demonstrate superior performance of the presented method not only in accordance with power line interference, but also in removing the distortion of the time-variant filters.

Evaluation of a damping coefficient influence made by notch filters on efficiency of ECG signals processing

Introduction. The aim of this study is to evaluate the effectof damping coefficient ξ provided by narrow-band notch filterson the quality indicators of the ECG signal processing accompaniedby development of a special software package forexperimental testing of the cascade filtering system of naturalelectrical noise and its harmonics.Materials and Methods. For the formation of additive componentsof signal and noise, test ECG signals from the MassachusettsInstitute of Technology were selected as a model, andelectrical noise was synthesized taking into account their harmonicnature. The transfer function of the notch filtering systemwas tuned and calculated. Quantitative quality metrics was usedto determine the processing efficiency at the input and output ofthe signal filtering system. To assess the effect of damping coefficientsmade on the ECG signal processing system, the method ofthe linear regression analysis was applied. Methods of structuraland procedural programming were used to create a softwarepackage for processing a full-scale noisy signal recording.Results. An increase in the efficiency of the ECG signal processingsystem was revealed when calculating quantitative indicatorscharacterizing the quality solution to the signal filteringproblem. It has been found that at values of the dampingcoefficient ξ = 0.1, the efficiency of the analysis of ECG signalprocessing in terms of accuracy and noise resistance increases,and the filtering error decreases due to the improvement ofthe selectivity of the notch filter at the resonant frequency. Theeffect of the damping coefficient on the quality indicators ofECG signal processing was established, and regression equationswere obtained to characterize the adequacy of the designedmodel for the confidence interval (P = 0.99) at p &lt;0.01.The performance of the developed software package has beendemonstrated, which combines a cascade filtering system witha damping coefficient ξ = 0.1, to eliminate the natural electricalinterference of the ECG signal and its harmonics.Conclusion. The evidence data obtained in our work, both calculated(theoretical) and practical (experimental) data, confirmthe efficiency of the proposed processing approach to the selectionof informative components ECG signal under the influenceof high-frequency electrical interference and its harmonics.The sequential incorporation of two narrow-band notchfilters with a damping coefficient ξ = 0.1 to suppress interferenceat a frequency of 50 Hz and its harmonics at a frequencyof 100 Hz opens up new possibilities for processing ECG signals.

Preserving Wideband Tympanometry Information With Artifact Mitigation.

Absorbance measured using wideband tympanometry (WBT) has been shown to be sensitive to changes in middle and inner ear mechanics, with potential to diagnose various mechanical ear pathologies. However, artifacts in absorbance due to measurement noise can obscure information related to pathologies and increase intermeasurement variability. Published reports frequently present absorbance that has undergone smoothing to minimize artifact; however, smoothing changes the true absorbance and can destroy important narrow-band characteristics such as peaks and notches at different frequencies. Because these characteristics can be unique to specific pathologies, preserving them is important for diagnostic purposes. Here, we identify the cause of artifacts in absorbance and develop a technique to mitigate artifacts while preserving the underlying WBT information. A newly developed Research Platform for the Interacoustics Titan device allowed us to study raw microphone recordings and corresponding absorbances obtained by WBT measurements. We investigated WBT measurements from normal hearing ears and ears with middle and inner ear pathologies for the presence of artifact and noise. Furthermore, it was used to develop an artifact mitigation procedure and to evaluate its effectiveness in mitigating artifacts without distorting the true WBT information. We observed various types of noise that can plague WBT measurements and that contribute to artifacts in computed absorbances, particularly intermittent low-frequency noise. We developed an artifact mitigation procedure that incorporates a high-pass filter and a Tukey window. This artifact mitigation resolved the artifacts from low-frequency noise while preserving characteristics in absorbance in both normal hearing ears and ears with pathology. Furthermore, the artifact mitigation reduced intermeasurement variability. Unlike smoothing algorithms used in the past, our artifact mitigation specifically removes artifacts caused by noise. It does not change frequency response characteristics, such as narrow-band peaks and notches in absorbance at different frequencies that can be important for diagnosis. Also, by reducing intermeasurement variability, the artifact mitigation can improve the test-retest reliability of these measurements.

Development of fast-ion collective Thomson scattering diagnostics for the GDT experiment

In this paper, we describe hardware developed for the collective Thomson scattering (CTS) diagnostic for the large open magnetic trap GDT (Budker Institute, Russia) used in fusion researches. The diagnostic utilizes 400 kW/54.5 GHz gyrotron as a source of probe radiation and is aimed at the reconstruction of fast ion distributions over transverse and longitudinal velocities driven by high-power neutral beam injection. Formation and manipulation of the probe beam and collection of the scattered microwave radiation are done with large-aperture quasi-optical mirror systems. The receiving complex consists of two identical channels for simultaneous detection of scattering in two complement geometries. Each channel includes a highly sensitive radiometer/spectrum analyzer with the band of 54.470 ± 0.550 GHz, the noise temperature of 0.35 eV, the sensitivity less than 0.025 eV, the frequency/time resolution of 5–50 MHz/10 μs, and narrow-band notch filter providing at least -40 dB rejection in the band of 25 MHz with a central frequency tunable in 54.470 ± 0.050 GHz for protection of the input RF circuit from a backlight of powerful gyrotron radiation.

Compact ultra-wideband monopole antenna with tunable notch bandwidth/frequency ratio

Abstract A compact tunable notch band ultra-wideband (UWB) antenna is implemented. The band notch characteristics have been obtained by placing a square-shaped metallic loop in the upper ground plane connected via PIN diode. The obtained notched frequency bandwidth can be altered by changing the states of the PIN diode. UWB response with narrow-band notch operation is observed when PIN diode is in ON state. When the PIN diode is in OFF state, the bandwidth of the obtained band notch widens by suppressing the first higher-order resonance and thus a narrow dual-band response is obtained. Moreover, the ratio of the frequency of first higher-order to the fundamental mode in the pass-band can be tuned with the different values as 1.584 and 2.20 in the ON and OFF state of the PIN diode, respectively. Furthermore, the antenna structure offers a compact geometry for the operation with the UWB response with band notch characteristics.

Development of the ion cyclotron emission diagnostic for the W7-X stellarator.

An ion cyclotron emission (ICE) diagnostic is prepared for installation into the W7-X stellarator, with the aim to be operated in the 2022 experimental campaign. The design is based on the successful ICE diagnostic on the ASDEX Upgrade tokamak. The new diagnostic consists of four B-dot probes, mounted about 72° toroidally away (one module) from the neutral beam injector, with an unobstructed plasma view. Two of the B-dot probes are oriented parallel to the local magnetic field, aimed to detect fast magnetosonic waves. The remaining two probes are oriented poloidally, with the aim to detect slow waves. The radio frequency (RF) signals picked up by the probes are transferred via 50 Ω vacuum-compatible coaxial cables to RF detectors. Narrow band notch filters are used to protect the detectors from possible RF waves launched by the W7-X antenna. The signal will be sampled with a four-channel fast analog-to-digital converter with 14 bit depth and 1 GSample/s sampling rate. The diagnostic's phase-frequency characteristic is properly measured in order to allow measuring the wave vectors of the picked up waves.

Synthesis design of wideband bandpass filter with narrow notch band

AbstractIn this article, a novel wideband bandpass filter (BPF) with narrow notch band is presented. It is composed of two sets of shunt microstrip‐to‐slotline vertical transitions, a coplanar waveguide (CPW) connecting line, and a meandering half‐wavelength slotline section. Utilizing the synthesis method based on the transmission line network, a four‐pole BPF with Chebyshev equal‐ripple frequency response is realized in the desired passband. The narrow notch band with 3‐dB fractional bandwidth (FBW) of 3% at the center frequency 2.75 GHz is introduced by an embedding meandering slotline stub. To verify the theoretical prediction, the proposed BPF is fabricated and measured. The circuit model and EM simulation are consistent with theoretical calculation and test results, which sufficiently confirm the correctness and feasibility of the design method.

Ultrawideband Frequency-Selective Absorber Designed With an Adjustable and Highly Selective Notch

In this article, the working mechanism of a wideband absorber designed with an adjustable and highly selective notch band is studied, in which the narrow notch band is independently controlled by the lower lossless layer of the absorber, whereas the upper lossy layer loaded with lumped resistors realizes absorption. We present two instances with geometrically controlled and electrically controlled notch bands, respectively. Without decreasing absorption performance, the notch position can be flexibly adjusted throughout the entire frequency band by simply modifying the dimension of the lossless frequency-selective surface (FSS) or changing the capacitance of the varactor, i.e., using geometric control or electrical control. The narrow notch band allows two wide absorption bands to be retained on both sides; therefore, good stealth performance is still guaranteed. Equivalent circuit models (ECMs) are proposed to further explain the principle. The frequency-domain simulation, ECM, time-domain simulation, and experimental results are in good agreement and validate the adjustability and high selectivity of the notched absorbers. At the end of this article, an FSA-backed monopole antenna is simulated and measured, which clearly illustrates that these FSAs can serve as the ground plane for antennas and realize out-of-band RCS reduction.

Adaptive Complex Filtering for Narrowband Jamming Mitigation in Resource-Constrained Wireless Networks

Jamming attacks present a major challenge for the physical layer security of wireless communication systems. Among the large number of existing methods for jamming mitigation, filtering is a simple but promisingly effective solution that can be applied in resource-constrained and low-power wireless networks. In this article, a first-order adaptive complex narrowband notch filter is proposed for use against high-power narrowband jamming attacks. The central frequency of the filter is adaptively adjustable to match the interfering frequency. This enables the proposed solution to perform effectively in the presence of a jammer whose frequency varies in fixed or random time periods. The simulation results demonstrate the filter's behavior and the efficiency of the proposed technique.

Tunable hybrid spectral filter and time-division multiplexing of second-order fluorescence controlled by phonon and dressing on Pr3+:YSO

Atom-like nonlinear responses of rare earth doped crystal Pr3+:Y2SiO5 (Pr3+: YSO) exhibit unique features compared with other nonlinear crystals. The responses become more interesting, while Pr3+: YSO is modulated simultaneously by temperature and multi-parameters related to dressed state. The generations of Stokes and fluorescence (FL) signals are demonstrated in both time and spectral domains. Here, we are presenting a new controlling strategy by interaction between dressing and phonon on Pr3+: YSO to manipulate the intensity of Stokes and FL signals. Interaction between dressing and phonon leads to more stable nonlinear response of the YSO crystal, which is very important for integrated quantum photonic device stability and multi-functionality. Also, we have realized tunable hybrid spectral filter (narrow-band pass notch filter (NBPNF), narrow-band stop notch filter (NBSNF)) and time-division multiplexing router on Pr3+: YSO by controlling the interaction between dressing and phonons. Tunable hybrid spectral filter and pure NBPNF are realized from dressing dip of Autler-Townes (AT) splitting and spectral intensity Stokes emission peak. Also, time-division multiplexing router is realized by time-domain adiabatic expansion. Furthermore, optical switch between tunable hybrid spectral filter to pure NBPNF is realized from dressing dip (AT splitting) to spectral intensity Stokes emission peak. Our experimental results suggests advanced technique for realizing tunable hybrid spectral filter with a contrast of about 98%, and optical time-division multiplexing router with channel equalization is about 85%.

CSRR Embedded CPW Band-Stop Filter

This paper proposes topologies for narrowband and broadband notch filters using complementary split ring resonators (CSRR) in coplanar waveguide (CPW) technology. Simple analysis justifies these topologies. Strong coupling between the resonator and the signal line in these topologies can reduce the radiation loss in the stop-bands. Characteristics of these filters realized from electromagnetic simulations match closely with those from measurements on prototypes.

Low-Power RF Signal Detection Using a High-Gain Tunable OEO Based on Equivalent Phase Modulation

A novel photonic method for low power radio-frequency (RF) signal detection by a tunable optoelectronic oscillator (OEO) with high gain based on equivalent phase modulation (EPM) is proposed and experimentally demonstrated. A dual-parallel Mach-Zehnder modulator is utilized to generate the EPM signal with a controllable optical carrier to sideband ratio, by which the gain to the RF signal by the OEO loop can be enhanced. A phase-shifted fiber Bragg grating (PS-FBG) with a narrow-band notch in its reflection band implements the phase modulation to intensity modulation conversion by removing one sideband of the EPM signal. The gain and noise performance of the detection system are theoretically analyzed and simulated. In the experiment, the maximum gain of 10.4 dB is obtained at 8 GHz, and the detection sensitivity for RF signals from 2 to 18 GHz are within the range of −87.7 to −84.3 dBm by using the developed detection system. Compared to normal phase modulation based scheme, the EPM-based system offers 9.1 dB higher gain. Utility of the proposed approach for detecting modulated RF signal is also investigated and an optimization scheme is discussed.

All-Dielectric Metasurface for Highly Tunable, Narrowband Notch Filtering

A novel scheme of an all-dielectric metasurface with double-layer patch array is proposed to achieve the highly tunable, narrowband notch filtering across visible and near-infrared range. The all-dielectric metasurface presents efficient blocking (transmittance 0.01–0.0001) at targeted wavelength and high (>93%) transmission across the visible and near-infrared light range outside the targeted wavelength band. The bandwidth of the notch filter could be greatly compressed with this all-dielectric metasurface, compared with those typical interference notch filters for distinctive wavelengths. The effect of the geometrical parameters on the spectral filtering of this metasurface is studied to provide a distinct relationship to design the desired narrowband notch filter conveniently. And the antireflection effect of the top silicon dioxide layer is verified with similar bandwidth, lower transmission at notch filtering wavelength and higher transmission at other wavelengths. In addition, the optical Fano resonance excited by the all-dielectric metasurface is responsible for the spectral filtering feature including the deep blocking feature at the specific wavelength and high transmission at other wavelengths.

Brillouin-Assisted Notch Filtering Based All-Optical Image Rejection Mixer

A novel approach for realizing a microwave photonic image rejection mixer is presented in this paper. It is based on using a widely tunable narrow-band optical notch filter implemented by stimulated Brillouin scattering (SBS) to remove the image signal. The image rejection mixer has a simple structure as it only requires a single integrated dual-polarization modulator for both frequency conversion and pump wave generation for the SBS process. The absence of electrical components enables the image rejection mixer to be operated over a wide frequency range with a high image rejection ratio. A technique is also proposed to suppress the noise generated by the SBS process in the image rejection mixer. Experimental results demonstrate a high and constant image rejection ratio of over 32 dB for the image rejection mixer operating over an RF signal frequency range of 11.8–19.6 GHz, and around −5 dB conversion efficiency.