Journal articles: 'Comb filtering'

1

Horn, J., M. Jansen, and S. J. Prange. "Adaptive comb-filtering using neural networks." IEEE Transactions on Consumer Electronics 43, no. 3 (1997): 833–36. http://dx.doi.org/10.1109/30.628727.

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2

Nehorai, A., and B. Porat. "Adaptive comb filtering for harmonic signal enhancement." IEEE Transactions on Acoustics, Speech, and Signal Processing 34, no. 5 (October 1986): 1124–38. http://dx.doi.org/10.1109/tassp.1986.1164952.

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Ferreira, José L., Yan Wu, and Ronald M. Aarts. "Enhancement of the Comb Filtering Selectivity Using Iterative Moving Average for Periodic Waveform and Harmonic Elimination." Journal of Healthcare Engineering 2018 (2018): 1–14. http://dx.doi.org/10.1155/2018/7901502.

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A recurring problem regarding the use of conventional comb filter approaches for elimination of periodic waveforms is the degree of selectivity achieved by the filtering process. Some applications, such as the gradient artefact correction in EEG recordings during coregistered EEG-fMRI, require a highly selective comb filtering that provides effective attenuation in the stopbands and gain close to unity in the pass-bands. In this paper, we present a novel comb filtering implementation whereby the iterative filtering application of FIR moving average-based approaches is exploited in order to enhance the comb filtering selectivity. Our results indicate that the proposed approach can be used to effectively approximate the FIR moving average filter characteristics to those of an ideal filter. A cascaded implementation using the proposed approach shows to further increase the attenuation in the filter stopbands. Moreover, broadening of the bandwidth of the comb filtering stopbands around −3 dB according to the fundamental frequency of the stopband can be achieved by the novel method, which constitutes an important characteristic to account for broadening of the harmonic gradient artefact spectral lines. In parallel, the proposed filtering implementation can also be used to design a novel notch filtering approach with enhanced selectivity as well.

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Hu, H. T. "Robust pitch estimation based on modified comb filtering approach." Electronics Letters 43, no. 25 (2007): 1471. http://dx.doi.org/10.1049/el:20071953.

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Wen Jin, Xin Liu, M. S. Scordilis, and Lu Han. "Speech Enhancement Using Harmonic Emphasis and Adaptive Comb Filtering." IEEE Transactions on Audio, Speech, and Language Processing 18, no. 2 (February 2010): 356–68. http://dx.doi.org/10.1109/tasl.2009.2028916.

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Ferreiro, T. I., T. P. Lamour, J. Sun, and D. T. Reid. "1.4 GHz femtosecond comb generation by Fabry‐Pérot filtering of optical parametric oscillator frequency comb." Electronics Letters 49, no. 13 (June 2013): 833–35. http://dx.doi.org/10.1049/el.2013.1504.

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7

Kitamura, Toshiaki. "Comb-Line Filter with Coupling Capacitor in Ground Plane." Active and Passive Electronic Components 2011 (2011): 1–6. http://dx.doi.org/10.1155/2011/919240.

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A comb-line filter with a coupling capacitor in the ground plane is proposed. The filter consists of two quarter-wavelength microstrip resonators. A coupling capacitor is inserted into the ground plane in order to build strong coupling locally along the resonators. The filtering characteristics are investigated through numerical simulations as well as experiments. Filtering characteristics that have attenuation poles at both sides of the passband are obtained. The input susceptances of even and odd modes and coupling coefficients are discussed. The filters using stepped impedance resonators (SIRs) are also discussed, and the effects of the coupling capacitor for an SIR structure are shown.

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Nishiyama, Akiko, Satoru Yoshida, Takuya Hariki, Yoshiaki Nakajima, and Kaoru Minoshima. "Sensitivity improvement of dual-comb spectroscopy using mode-filtering technique." Optics Express 25, no. 25 (December 6, 2017): 31730. http://dx.doi.org/10.1364/oe.25.031730.

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Šmíd, R., A. Hänsel, L. Pravdová, J. Sobota, O. Číp, and N. Bhattacharya. "Comb mode filtering silver mirror cavity for spectroscopic distance measurement." Review of Scientific Instruments 87, no. 9 (September 2016): 093107. http://dx.doi.org/10.1063/1.4962681.

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10

Hu, H. T. "Comb filtering of noisy speech using overlap-and-add approach." Electronics Letters 34, no. 1 (1998): 16. http://dx.doi.org/10.1049/el:19980107.

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11

Zhang, Heng, Jun Yao, Feng Gang Tao, and Xu Ye Zhuang. "MEMS Grating with Interdigitated-Comb Structure." Key Engineering Materials 503 (February 2012): 49–54. http://dx.doi.org/10.4028/www.scientific.net/kem.503.49.

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Grating as an important spectral component can be applied to spectral analysis, filtering, dispersion compensation, sensing and so on. Their advantages are compactness, potentially high actuation speed and the ability to deflect light at large angles. In this paper, a MEMS interdigitated-comb grating actuated by a comb-drive actuator is presented. An experiment is performed to demonstrate how the proposed grating works with an applied voltage. At 85V, the displacement of comb-drive actuator can achieve 2.1μm; accordingly the gap between the interdigitated-comb gratings varies by 2.1μm. The mechanical and the optical sensing properties of the MEMS grating are both analyzed in this paper. This grating can be widely used in optical sensor and to detect the micro-displacement.

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Wu, Rui, Minhyup Song, Daniel E. Leaird, and Andrew M. Weiner. "Comb-based radio-frequency photonic filtering with 20 ns bandwidth reconfiguration." Optics Letters 38, no. 15 (July 24, 2013): 2735. http://dx.doi.org/10.1364/ol.38.002735.

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Cramer, Claire E., Chih-Hao Li, Andrew J. Benedick, Alexander G. Glenday, Franz X. Kärtner, David F. Phillips, Dimitar Sasselov, Andrew Szentgyorgyi, and Ronald L. Walsworth. "Astro-comb: revolutionizing precision spectroscopy in astrophysics." Proceedings of the International Astronomical Union 4, S253 (May 2008): 499–501. http://dx.doi.org/10.1017/s174392130802704x.

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AbstractSearches for extrasolar planets using the periodic Doppler shift of stellar spectral lines have recently achieved a precision better than 60cm/s. To find a 1-Earth mass planet in an Earth-like orbit, a precision of 5cm/s is necessary. The combination of a laser frequency comb with a Fabry-Perot filtering cavity has been suggested as a promising approach to achieve such Doppler shift resolution via improved spectrograph wavelength calibration. Here we report the fabrication of such a filtered laser comb with up to 40 GHz (~1 Angstrom) line spacing, generated from a 1 GHz repetition-rate source, without compromising long-term stability, reproducibility or spectral resolution. This wide-line-spacing comb (astro-comb) is well matched to the resolving power of high-resolution astrophysical spectrographs. The astrocomb should allow a precision as high as 1cm/s in astronomical readial velocity measurements.

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Pei, Jihong, Mi Zou, and Yang Zhao. "Adaptive comb-type filtering method for stripe noise removal in infrared images." Journal of Electronic Imaging 28, no. 01 (February 18, 2019): 1. http://dx.doi.org/10.1117/1.jei.28.1.013037.

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MK, Varun, Akhileshwar Mishra, and Ravi Pant. "Slow-light based tunable delay and narrowband comb filtering at 2 μm." Optics Letters 44, no. 21 (October 28, 2019): 5278. http://dx.doi.org/10.1364/ol.44.005278.

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Troncoso Romero, David Ernesto, Massimiliano Laddomada, and Gordana Jovanovic Dolecek. "Optimal Sharpening of Compensated Comb Decimation Filters: Analysis and Design." Scientific World Journal 2014 (2014): 1–9. http://dx.doi.org/10.1155/2014/950860.

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Comb filters are a class of low-complexity filters especially useful for multistage decimation processes. However, the magnitude response of comb filters presents a droop in the passband region and low stopband attenuation, which is undesirable in many applications. In this work, it is shown that, for stringent magnitude specifications, sharpening compensated comb filters requires a lower-degree sharpening polynomial compared to sharpening comb filters without compensation, resulting in a solution with lower computational complexity. Using a simple three-addition compensator and an optimization-based derivation of sharpening polynomials, we introduce an effective low-complexity filtering scheme. Design examples are presented in order to show the performance improvement in terms of passband distortion and selectivity compared to other methods based on the traditional Kaiser-Hamming sharpening and the Chebyshev sharpening techniques recently introduced in the literature.

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Rutkowski, Lucile, and Jérôme Morville. "Broadband cavity-enhanced molecular spectra from Vernier filtering of a complete frequency comb." Optics Letters 39, no. 23 (November 24, 2014): 6664. http://dx.doi.org/10.1364/ol.39.006664.

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18

Bao-Jian, Wu, Lu Xin, and Qiu Kun. "Magneto-Optic Fiber Gratings Useful for Dynamic Dispersion Management and Tunable Comb Filtering." Chinese Physics Letters 27, no. 6 (June 2010): 067803. http://dx.doi.org/10.1088/0256-307x/27/6/067803.

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19

Torres-Company, Victor, Daniel E. Leaird, and Andrew M. Weiner. "Simultaneous broadband microwave downconversion and programmable complex filtering by optical frequency comb shaping." Optics Letters 37, no. 19 (September 20, 2012): 3993. http://dx.doi.org/10.1364/ol.37.003993.

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20

Zhu, Dan Dan, and Hai Fang Wang. "The Application of Wavelet Denoise in Sampled Grating Comb Filter." Advanced Materials Research 1042 (October 2014): 135–38. http://dx.doi.org/10.4028/www.scientific.net/amr.1042.135.

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This paper based on the theoretical basis of sampled fiber grating, using transfer matrix method to analyze sampled fiber grating. By changing the parameters of sampled fiber grating and simulating its reflective spectrum. Four optical comb filters based on sampled grating were designed. Then the wavelet de-noising principle was introduced. In order to optimize designing of sampling grating comb filter, a filtering analysis and denoising method by using wavelet analysis to denoise was proposed. Finally, the automatic one-dimensional denoising was used with db6 wavelet. It not only denoise reflective spectrum noise, but also play a certain inhibition in the side-lobe interference the signal received. The smooth reflective spectrum can be got after denoising.

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Siciliani de Cumis, Mario, Roberto Eramo, Jie Jiang, Martin E. Fermann, and Pablo Cancio Pastor. "Direct Comb Vernier Spectroscopy for Fractional Isotopic Ratio Determinations." Sensors 21, no. 17 (August 31, 2021): 5883. http://dx.doi.org/10.3390/s21175883.

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Accurate isotopic composition analysis of the greenhouse-gasses emitted in the atmosphere is an important step to mitigate global climate warnings. Optical frequency comb–based spectroscopic techniques have shown ideal performance to accomplish the simultaneous monitoring of the different isotope substituted species of such gases. The capabilities of one such technique, namely, direct comb Vernier spectroscopy, to determine the fractional isotopic ratio composition are discussed. This technique combines interferometric filtering of the comb source in a Fabry–Perot that contains the sample gas, with a high resolution dispersion spectrometer to resolve the spectral content of each interacting frequency inside of the Fabry–Perot. Following this methodology, simultaneous spectra of ro-vibrational transitions of 12C16O2 and 13C16O2 molecules are recorded and analyzed with an accurate fitting procedure. Fractional isotopic ratio 13C/12C at 3% of precision is measured for a sample of CO2 gas, showing the potentialities of the technique for all isotopic-related applications of this important pollutant.

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22

Mildner, Jutta, Karl Meiners-Hagen, and Florian Pollinger. "Dual-frequency comb generation with differing GHz repetition rates by parallel Fabry–Perot cavity filtering of a single broadband frequency comb source." Measurement Science and Technology 27, no. 7 (May 31, 2016): 074011. http://dx.doi.org/10.1088/0957-0233/27/7/074011.

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Rutkowski, Lucile, and Jérôme Morville. "Continuous Vernier filtering of an optical frequency comb for broadband cavity-enhanced molecular spectroscopy." Journal of Quantitative Spectroscopy and Radiative Transfer 187 (January 2017): 204–14. http://dx.doi.org/10.1016/j.jqsrt.2016.09.021.

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24

McKinney, Jason D., Daniel E. Leaird, Alex S. Hastings, Andrew M. Weiner, and Keith J. Williams. "Optical Comb Sources and High-Resolution Optical Filtering for Measurement of Photodiode Harmonic Distortion." Journal of Lightwave Technology 28, no. 8 (April 2010): 1228–35. http://dx.doi.org/10.1109/jlt.2010.2044632.

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25

Jain, Sourabh, Sulabh Srivastava, Swati Rajput, Lalit Singh, Pragya Tiwari, Arvind K. Srivastava, and Mukesh Kumar. "Thermally Stable Optical Filtering Using Silicon-Based Comb-Like Asymmetric Grating for Sensing Applications." IEEE Sensors Journal 20, no. 7 (April 1, 2020): 3529–35. http://dx.doi.org/10.1109/jsen.2019.2960604.

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26

Nakajima, Yoshiaki, Takuya Hariki, Akiko Nishiyama, and Kaoru Minoshima. "Phase-stabilized all-fiber-based mode-filtering technique for generating a gigahertz frequency comb." Optics Express 28, no. 12 (May 27, 2020): 17502. http://dx.doi.org/10.1364/oe.393824.

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27

Li, Mengxian, Yiqing Shu, Lin Gu, Zhengwei Cui, Aiping Luo, Yongyao Li, and Weicheng Chen. "Modulated comb-like pulse distribution induced by intracavity Sagnac filtering in a fiber laser." Optics & Laser Technology 145 (January 2022): 107480. http://dx.doi.org/10.1016/j.optlastec.2021.107480.

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Xu Qin-Fang, Yin Mo-Juan, Kong De-Huan, Wang Ye-Bing, Lu Ben-Quan, Guo Yang, and Chang Hong. "Optical frequency comb active filtering and amplification for second cooling laser of strontium optical clock." Acta Physica Sinica 67, no. 8 (2018): 080601. http://dx.doi.org/10.7498/aps.67.20172733.

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29

Tsang, Peter W. M., Jung-Ping Liu, Hoson Lam, and Ting-Chung Poon. "Enhancing the Quality of Sampled Phase-Only Hologram (SPOH) Based on Time-Division Comb Filtering." Applied Sciences 10, no. 8 (April 15, 2020): 2732. http://dx.doi.org/10.3390/app10082732.

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Generation of digital phase-only Fresnel holograms is an important research area in digital holography, as it leads to a substantial simplification of a holographic display system. However, the quality of the reconstructed image of a hologram without the magnitude component is heavily degraded. The problem can be reduced by down-sampling the intensity of an image prior to generating the hologram. The method, referred to as “sampled phase-only hologram” (SPOH) generation, results in reconstructed images that are masked with the pattern of the down-sampling lattice. This paper reports a novel, low complexity method to alleviate this problem through the concept of comb filtering. Results reveal prominent enhancement on the reconstructed image of a SPOH.

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Wu, Rui, Christopher M. Long, Daniel E. Leaird, and Andrew M. Weiner. "Directly Generated Gaussian-Shaped Optical Frequency Comb for Microwave Photonic Filtering and Picosecond Pulse Generation." IEEE Photonics Technology Letters 24, no. 17 (September 2012): 1484–86. http://dx.doi.org/10.1109/lpt.2012.2205673.

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Zhang, Yun Dong, Jin Li, Han Yang Li, and Ping Yuan. "The Optical Response of Trapezoidal Comb-Like Nanostructures." Applied Mechanics and Materials 284-287 (January 2013): 2816–20. http://dx.doi.org/10.4028/www.scientific.net/amm.284-287.2816.

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Metal nanostructures can be used to control light transmission on the nanometer scale. In this paper, we propose a ladder-type comb-like metal nano-grating structure, based on optical filtering properties of the comb-like nanostructures and surface plasmon resonance effect of the metal nano-structures. The comb part of the structure is the silver nano-grating with the width of 20nm and a depth difference of 5nm between the adjacent gratings. We use the 532nm CW laser as the incident light source to study the reflective properties of the P polarized light and calculate the reflected power spectrum of the structure in three different parameters, which are the silver nano-grating, the silver-air nano-grating (silver grating are separated by air) and silver-SiO2 nano-grating. The experimental results show that the light wave oscillation modes are closely related to the comb-like structure parameters (including the depth and width) on the power spectrum. Meanwhile, we also draw conclusions that different intervention media does not change the position of the light wave oscillation modes, but only a significant effect on the reflection intensity of the different modes. Furthermore, we also noted that the depth of silver nano-gratings can affect the position of the resonance peak. As the waveguide depth of the silver nano-gratings increasing, the spacing of different modes’ oscillation peak is becoming larger. Based on the finding, we can modulate the light wave oscillation modes in a very wide spectral range. The results of this paper will promote the development of the optical filter, light wave mode selection and random laser excitation.

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Santhanam, Balasubramaniam, and Petros Maragos. "Harmonic analysis and restoration of separation methods for periodic signal mixtures: Algebraic separation versus comb filtering." Signal Processing 69, no. 1 (August 1998): 81–91. http://dx.doi.org/10.1016/s0165-1684(98)00088-7.

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Nakajima, Yoshiaki, Akiko Nishiyama, and Kaoru Minoshima. "Mode-filtering technique based on all-fiber-based external cavity for fiber-based optical frequency comb." Optics Express 26, no. 4 (February 13, 2018): 4656. http://dx.doi.org/10.1364/oe.26.004656.

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Yang, Ruitao, Haisu Lv, Jing Luo, Pengcheng Hu, Hongxing Yang, Haijin Fu, and Jiubin Tan. "Ultrastable Offset-Locking Continuous Wave Laser to a Frequency Comb with a Compound Control Method for Precision Interferometry." Sensors 20, no. 5 (February 25, 2020): 1248. http://dx.doi.org/10.3390/s20051248.

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A simple and robust analog feedforward and digital feedback compound control system is presented to lock the frequency of a slave continuous wave (CW) laser to an optical frequency comb. The beat frequency between CW laser and the adjacent comb mode was fed to an acousto-optical frequency shifter (AOFS) to compensate the frequency dithering of the CW laser. A digital feedback loop was achieved to expand the operation bandwidth limitation of the AOFS by over an order of magnitude. The signal-to-noise ratio of the interference signal was optimized using a grating-based spectral filtering detection unit. The complete system achieved an ultrastable offset-locking of the slave CW laser to the frequency comb with a relative stability of ±3.62 × 10−14. The Allan deviations of the beat frequency were 8.01 × 10−16 and 2.19 × 10−16 for a gate time of 10 s and 1000 s, respectively. The findings of this study may further improve laser interferometry by providing a simple and robust method for ultrastable frequency control.

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Bai, Mingsian R., and Kwuen-Yieng Ou. "Synthesis of Room Responses Using the Virtual Source Representation and the Comb-Nested Allpass Filters." Journal of Vibration and Acoustics 128, no. 6 (October 9, 2005): 690–98. http://dx.doi.org/10.1115/1.2360951.

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An artificial reverberator is proposed in this paper to synthesize room responses. The method employs the virtual source representation and the comb-nested allpass filters to generate the early reflection and late reverberation, respectively, of room responses. The virtual source method is based on a simple representation of sound field with a distribution of discrete simple sources on the boundary. The complex strengths of the virtual sources are then calculated by solving a frequency domain least-square problem. Parameters such as room geometry, size, and wall absorption are naturally incorporated into the synthesis process. The filtering property of human hearing is also exploited in a nonuniform sampling procedure to further simplify the computation. Apart from the early reflection, a comb-allpass filter network is adopted to simulate late reverberations. Optimal parameters of the comb-allpass filter network are obtained using the genetic algorithm (GA). The energy decay curve (EDC) is chosen as the objective function in the GA procedure. Numerical simulations are carried out for a rectangular room and a concert hall model to verify the proposed technique. Subjective listening experiments demonstrate that the present technique is capable of conferring remarkable realism of room responses.

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Hou, Lei, Hai-Nian Han, Wei Wang, Long Zhang, Li-Hui Pang, De-Hua Li, and Zhi-Yi Wei. "A 23.75-GHz frequency comb with two low-finesse filtering cavities in series for high resolution spectroscopy." Chinese Physics B 24, no. 2 (February 2015): 024213. http://dx.doi.org/10.1088/1674-1056/24/2/024213.

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Caraquitena, José, and Javier Martí. "High-rate pulse-train generation by phase-only filtering of an electrooptic frequency comb: Analysis and optimization." Optics Communications 282, no. 18 (September 2009): 3686–92. http://dx.doi.org/10.1016/j.optcom.2009.06.017.

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Villa, Carlos, Michael Hayduk, and Eric Donkor. "Terahertz Optical Frequency Comb Generation by Spectral Filtering of Broadband Spontaneous Amplified Emissions From a Semiconductor Optical Amplifier." Journal of Lightwave Technology 27, no. 23 (December 2009): 5437–41. http://dx.doi.org/10.1109/jlt.2009.2026722.

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Ustinavičius, Tomas. "DIGITAL PROCESSING OF INVESTIGATED DAC’S SIGNALS." Mokslas - Lietuvos ateitis 2, no. 1 (February 28, 2010): 45–49. http://dx.doi.org/10.3846/mla.2010.010.

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The article shows that in designed algorithm for determination of digital signal processing and settling time of DAC the greatest influence on the test has 1/f type internal noise of the sampling converter. It is offered to filter the preliminary digital signal and to construct pseudo-periodic sequence from n realization periods of examined signals and internal noise. It is shown, that standard digital filters because of very high the demands are not suitable. The structure of digital comb filter is proposed. Investigations have shown that the given filter can effectively be used for filtering of various signals.

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Liu, Jingfei, and Nico F. Declercq. "Pulsed ultrasonic comb filtering effect and its applications in the measurement of sound velocity and thickness of thin plates." Ultrasonics 75 (March 2017): 199–208. http://dx.doi.org/10.1016/j.ultras.2016.12.003.

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Schmeissner, Roman, Valerian Thiel, Clément Jacquard, Claude Fabre, and Nicolas Treps. "Analysis and filtering of phase noise in an optical frequency comb at the quantum limit to improve timing measurements." Optics Letters 39, no. 12 (June 11, 2014): 3603. http://dx.doi.org/10.1364/ol.39.003603.

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Condon, Marissa, and Brendan Hayes. "Control of limit cycles in buck converters." COMPEL: The International Journal for Computation and Mathematics in Electrical and Electronic Engineering 33, no. 4 (July 1, 2014): 1448–61. http://dx.doi.org/10.1108/compel-09-2013-0293.

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Purpose – The purpose of this paper is to investigate limit cycles in digitally Proportional, Integral and Derivative (PID) controlled buck regulators. Filtering is examined as a means of removing the limit cycles in digitally controlled buck regulators. Design/methodology/approach – The paper explains why limit cycles occur in a digitally PID controlled buck converter. It then proceeds to propose two filters for their elimination. Results indicate the effectiveness of each of the filters. Findings – The paper gives a mathematical analysis of the occurrence of limit cycles in digitally controlled PID buck regulators. It finds that notch and comb filters are effective for the purpose of eliminating limit cycles in buck regulators. Originality/value – The paper employs a model of the buck regulator inclusive of the inductor loss – this was not done to date for this type of work. The paper analyses PID control. This was not done in the manner given. The paper addresses filtering as a means of removing limit cycles. It examines the effect of changing the digital controller parameters on the requirements of the filters.

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Cao, Hui, Youjian Song, Yuepeng Li, Runmin Li, Haosen Shi, Jiahe Yu, Minglie Hu, and Chingyue Wang. "Reduction of Moving Target Time-of-Flight Measurement Uncertainty in Femtosecond Laser Ranging by Singular Spectrum Analysis Based Filtering." Applied Sciences 8, no. 9 (September 12, 2018): 1625. http://dx.doi.org/10.3390/app8091625.

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Femtosecond laser ranging has drawn great interest in recent years, particularly based on an asynchronous optical sampling implementation where a pair of femtosecond lasers are used. High precision absolute ranging either relies on tightly-phase-locked optical frequency combs (a dual-comb setup) or multiple averaging of the measurements from two free-running femtosecond lasers. The former technique is too complicated for practical applications, while the latter technique does not apply to moving targets. In this report, we propose a new route to utilizing a powerful singular spectrum analysis (SSA) filtering method to improve femtosecond laser ranging precision for moving targets with acceleration. The SSA method is capable of separating complex patterns in signals without a priori knowledge of the dynamical model. Here, we utilize the basic SSA filter to extract the target trajectory in the presence of measurement noise both in numerical simulation and in the absolute ranging experiment based on a pair of free-running femtosecond lasers. The experimentally-achieved absolute ranging uncertainty of a moving target is well below 110 nm at a 200-Hz update rate by applying the basic SSA filter. This method paves the way to the practical applications of femtosecond absolute ranging for dynamic objects.

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Silva, C. F. C., A. J. Seeds, and P. J. Williams. "Terahertz span >60-channel exact frequency dense WDM source using comb generation and SG-DBR injection-locked laser filtering." IEEE Photonics Technology Letters 13, no. 4 (April 2001): 370–72. http://dx.doi.org/10.1109/68.917856.

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Azam, S. M. Kayser, Muhammad I. Ibrahimy, S. M. A. Motakabber, A. K. M. Zakir Hossain, and Md Shazzadul Islam. "A miniaturized hairpin resonator for the high selectivity of WLAN bandwidth." Bulletin of Electrical Engineering and Informatics 8, no. 3 (September 1, 2019): 916–22. http://dx.doi.org/10.11591/eei.v8i3.1496.

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In this article, a miniaturized hairpin resonator has been presented to introduce the high selectivity of Wireless Local Area Network (WLAN) bandwidth. In the construction of the hairpin resonator, short-circuited comb-lines are electrically coupled with the two longer edges of a rectangular-shaped loop. The hairpin resonator has been designed and fabricated with the Taconic TLX-8 substrate with a center-frequency at 2.45 GHz. The resonator exhibits a second order quasi-Chebyshev bandpass response. A low insertion loss has been found as -0.36 dB with a minimum return loss as -36.71 dB. The filtering dimension of this hairpin resonator occupies a small area of 166.82 mm2. This hairpin resonator is highly selective for the bandpass applications of the entire WLAN bandwidth.

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Rämö, Jussi, and Vesa Välimäki. "Digital Augmented Reality Audio Headset." Journal of Electrical and Computer Engineering 2012 (2012): 1–13. http://dx.doi.org/10.1155/2012/457374.

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Augmented reality audio (ARA) combines virtual sound sources with the real sonic environment of the user. An ARA system can be realized with a headset containing binaural microphones. Ideally, the ARA headset should be acoustically transparent, that is, it should not cause audible modification to the surrounding sound. A practical implementation of an ARA mixer requires a low-latency headphone reproduction system with additional equalization to compensate for the attenuation and the modified ear canal resonances caused by the headphones. This paper proposes digital IIR filters to realize the required equalization and evaluates a real-time prototype ARA system. Measurements show that the throughput latency of the digital prototype ARA system can be less than 1.4 ms, which is sufficiently small in practice. When the direct and processed sounds are combined in the ear, a comb filtering effect is brought about and appears as notches in the frequency response. The comb filter effect in speech and music signals was studied in a listening test and it was found to be inaudible when the attenuation is 20 dB. Insert ARA headphones have a sufficient attenuation at frequencies above about 1 kHz. The proposed digital ARA system enables several immersive audio applications, such as a virtual audio tourist guide and audio teleconferencing.

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El kadmiri, Ilyass, Youssef Ben-Ali, Aissam Khaled, and Driss Bria. "Acoustic filtering and guiding by the presence of a defect at the opened resonators level’s in one-dimensional comb-like phononic structure." Materials Today: Proceedings 31 (2020): S33—S40. http://dx.doi.org/10.1016/j.matpr.2020.05.552.

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Liu, Zichen, Chao Li, Jin Tao, and Shaohua Yu. "Programmable High-Resolution Spectral Processor in C-band Enabled by Low-Cost Compact Light Paths." Photonics 7, no. 4 (December 7, 2020): 127. http://dx.doi.org/10.3390/photonics7040127.

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The flexible photonics spectral processor (PSP) is an indispensable element for elastic optical transmission networks that adopt wavelength division multiplexing (WDM) technology. The resolution and system cost are two vital metrics when developing a PSP. In this paper, a high-resolution 1 × 6 programmable PSP is investigated and experimentally demonstrated by using low-cost compact spatial light paths, which is enabled by a 2 K (1080p) liquid crystal on silicon (LCoS) and two cascaded transmission gratings with a 1000 line/mm resolution. For each wavelength channel, the filtering bandwidth and power attenuation can be manipulated independently. The total insertion loss (IL) for six ports is in the range of 5.9~9.4 dB over the full C-band. The achieved 3-dB bandwidths are able to adjust from 6.2 GHz to 5 THz. Furthermore, multiple system experiments utilizing the proposed PSP, such as flexible spectral shaping and optical frequency comb generation, are carried out to validate the feasibility for the WDM systems.

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Mewada, Hiren K., and Jitendra Chaudhari. "Low computation digital down converter using polyphase IIR filter." Circuit World 45, no. 3 (August 5, 2019): 169–78. http://dx.doi.org/10.1108/cw-02-2019-0015.

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Purpose The digital down converter (DDC) is a principal component in modern communication systems. The DDC process traditionally entails quadrature down conversion, bandwidth reducing filters and commensurate sample rate reduction. To avoid group delay, distortion linear phase FIR filters are used in the DDC. The filter performance specifications related to deep stopband attenuation, small in-band ripple and narrow transition bandwidth lead to filters with a large number of coefficients. To reduce the computational workload of the filtering process, filtering is often performed as a two-stage process, the first stage being a down sampling Hoegenauer (or cascade-integrated comb) filter and a reduced sample rate FIR filter. An alternative option is an M-Path polyphase partition of a band cantered FIR filter. Even though IIR filters offer reduced workload to implement a specific filtering task, the authors avoid using them because of their poor group delay characteristics. This paper aims to propose the design of M-path, approximately linear phase IIR filters as an alternative option to the M-path FIR filter. Design/methodology/approach Two filter designs are presented in the paper. The first approach uses linear phase IIR low pass structure to reduce the filter’s coefficient. Whereas the second approach uses multipath polyphase structure to design approximately linear phase IIR filter in DDC. Findings The authors have compared the performance and workload of the proposed polyphase structured IIR filters with state-of-the-art filter design used in DDC. The proposed design is seen to satisfy tight design specification with a significant reduction in arithmetic operations and required power consumption. Originality/value The proposed design is an alternate solution to the M-path polyphase FIR filter offering very less number of coefficients in the filter design. Proposed DDC using polyphase structured IIR filter satisfies the requirement of linear phase with the least number of computation cost in comparison with other DDC structure.

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Pack, A. I., D. A. Silage, R. P. Millman, H. Knight, E. T. Shore, and D. C. Chung. "Spectral analysis of ventilation in elderly subjects awake and asleep." Journal of Applied Physiology 64, no. 3 (March 1, 1988): 1257–67. http://dx.doi.org/10.1152/jappl.1988.64.3.1257.

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We studied the periodicities of ventilation in elderly subjects using digital comb filtering. Two groups of subjects were studied, those with and without sleep apnea. Measurements were made in wakefulness, stage 1-2 sleep, and where possible in stage 3-4 sleep. For each of the digital filters we calculated the average power of the oscillatory output. To compare subject groups we first specifically determined the average power in the filter with the maximum output. The mean of this measurement was greater in elderly subjects with apnea compared with those without apnea, both during wakefulness and stage 1-2 sleep. In both groups of subjects the cycle time of the major ventilatory oscillations was on the order of 40-60 s. There was no difference in this cycle time between the two groups of subjects in wakefulness or stage 1-2 sleep. Thus, whereas similar oscillatory processes occur in subjects with and without apnea, it is the magnitude of the oscillation that differs between the two groups. These conclusions are supported by analysis of the output of individual filters of the digital comb filter. In both groups, stage 1-2 sleep produced significantly increased oscillations in ventilation. Both in wakefulness and stage 1-2 sleep, significantly greater periodicities occurred in the apneic compared with the nonapneic group. In the few subjects who had sufficient data in stage 3-4 sleep for spectral analysis, ventilatory oscillations were virtually absent in this state. Our data suggest that subjects who develop apnea during sleep have an increased propensity for periodic breathing even while awake.

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Journal articles on the topic 'Comb filtering'

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