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Project 1: Guitar Special Effects
Published in Thad B. Welch, Cameron H.G. Wright, Michael G. Morrow, ® to C with the TMS320C6x DSPs, 2016
Thad B. Welch, Cameron H.G. Wright, Michael G. Morrow
A notch filter is similar to a comb filter, but rather than having multiple evenly spaced stopbands, it has only a single stopband. An example frequency response of a notch filter is shown in Figure 10.10. Ideally, both the “sharpness” of the stopband and the location of the stopband on the frequency axis would be adjustable. An efficient and versatile design that achieves this is defined by the notch filter shown in Figure 10.4, which has the transfer function of H(z)=G1−2βz−1+z−21+2rβz−1−r2z−20≤r<1,−1≤β≤1
Digital communication
Published in John Watkinson, An Introduction to Digital Video, 2012
In practice, ATSC transmissions will experience co-channel interference from NTSC transmitters and the ATSC scheme allows the use of an NTSC rejection filter. Figure 9.47 shows that most of the energy of NTSC is at the carrier, subcarrier and sound carrier frequencies. A comb filter with a suitable delay can produce nulls or notches at these frequencies. However, the delay-and-add process in the comb filter also causes another effect. When two eight-level signals are added together, the result is a sixteen-level signal. This will be corrupted by noise of half the level that would corrupt an eight-level signal. However, the sixteen-level signal contains redundancy because it corresponds to the combinations of four bits whereas only two bits are being transmitted. This allows a form of error correction to be used.
Communication systems
Published in John Watkinson, Convergence in Broadcast and Communications Media, 2001
In practice ATSC transmissions will experience co-channel interference from NTSC transmitters and the ATSC scheme allows the use of an NTSC rejection filter. Figure 12.52 shows that most of the energy of NTSC is at the carrier, subcarrier and sound carrier frequencies. A comb filter with a suitable delay can produce nulls or notches at these frequencies. However, the delay-and-add process in the comb filter also causes another effect. When two eight-level signals are added together, the result is a sixteen-level signal. This will be corrupted by noise of half the level that would corrupt an eight-level signal. However, the sixteen-level signal contains redundancy because it corresponds to the combinations of four bits whereas only two bits are being transmitted. This allows a form of error correction to be used.
Multiband pass FIR integrator based on prediction and forecasting of coefficients
Published in International Journal of Electronics, 2022
Sumit Bhardwaj, Ashwni Kumar, R. L. Yadava
Zhen Zhang et al. (2018) designed Rogowski integrator by using the combination of comb filter with low pass filter and high pass filter for signal processing system application. Also, Tiago et al (2019) implemented a resettable generalised integrator of the second order for the phase-locked loop in the time domain. The proposed integrator finds its application to be used for any FPGA-based hardware control system, microprocessor, microcontroller, etc. Shan and Ren (2019) used quadrature and in-phase modulation for improved cascaded integrator based on the Comb filter. Working towards the experimental dimension, Fei and Parth (2019) used integrator for developing time to the digital integrator. Sharma and Rawat (2019) implemented IIR integrator for fractional order using FPGA using algorithm namely Ant Lion optimisation. Chavan and Aradhya (2020) merged integrator with downsampler and differentiator to create a special kind of filter for higher order using HDL. Bhardwaj et al. (2020), using Z-Transform and zero forcing algorithm, designed FIR integrator for Nyquist range and specific frequency for the band. Parekh et al. (2020) designed an integrator using CMOS and TSMC technology for VLSI applications.
Generation of mode-locked noise-like pulses in double-clad Tm-doped fibre laser with nonlinear optical loop mirror
Published in Journal of Modern Optics, 2020
H. Ahmad, M. H. M. Ahmed, M. Z. Samion
The generated SC is injected into the Sagnac loop mirror consisting of a 20 m-long of polarization maintaining fibre (PMF) in which spectral slicing occurs from the constructive and destructive interference of the two beams propagating in the loop. These combine after the coupler, which in this cavity functions as a comb filter (36). Figure 8 gives the magnified view of the sliced spectrum at four different wavelength regions, which demonstrate different wavelength spacings based on the length of the PMF and wavelength region as given in the equation: where and L are the modal birefringence difference between the slow-axis and fast-axis and the length of PMF respectively. Spacings of 0.35, 0.37, 0.45 and 0.49 nm are obtained at operating wavelengths of 1750, 1800, 1970 and 2070 nm respectively, and as the operating wavelength increases the spacing of the comb increases in tandem, auguring well with equation (1). The multi-wavelength output also shows a higher SNR of 12 dB at the mode locked region.
Wavelength switchable and stable single-longitudinal-mode erbium-doped fiber laser based on Mach–Zehnder interferometer and tunable filter
Published in International Journal of Optomechatronics, 2018
Wei He, Lianqing Zhu, Mingli Dong, Fei Luo
In the experiment, the pump laser’s (Oclaro Inc., USA) center wavelength was 976 nm, and the maximum output power was 500 mW. The EDF’s (EDFC-980-HP; Nufern, USA) absorption coefficient was 3 dB/m. The 2 × 2 circulator, WDM, and OC were manufactured by the Lightcomm Co., whereas the TF was produced by the Newport Co. First, the comb filter spectrum of the two-tapered MZI was fabricated and measured. In the experiment, the waist-enlarged taper was fabricated by the fiber fusion splicer (Fujikura 60S, Japan). First, two fibers’ end surface were cut flat and put on fiber holder of splicer; then, two fibers’ core alignment mode was used, and fiber overlap length was set as 15 μm during the splicing process. In the experiment, one taper was obtained and the image is shown in Figure 2(b), after two fibers were fused, the enlarged part of the cladding and core size was 170 and 12 μm, respectively. When the two-taper distance was 3 cm long, the MZI was constructed. As shown in Figure 3, when a broadband light was injected into the filter, the transmission comb spectrum was obtained, and a wavelength spacing of 2.5 nm and maximum stripe contrast of 5 dB was obtained. The transmission spectrum of the TF was tested in the experiment and is shown in Figure 4, where the 3-dB linewidth is 1.7 nm. The OSA resolution was 0.1 nm (Yokogawa Co.).