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Published in Philip A. Laplante, Comprehensive Dictionary of Electrical Engineering, 2018
attenuation constant the real part of the complex propagation constant for an electromagnetic wave. attenuator a device or network that absorbs part of a signal while passing the remainder with minimal distortion. attractor an asymptotic state of a dynamical system of which there are three basic types. Either (i) the system comes to rest and the attractor is a fixed point in state space, (ii) the system settles into a periodic motion known as a limit cycle, or (iii) the system enters a chaotic motion, in which case the attractor is called strange. attribute a special function in Pawlak's information system. Pawlak's information system S is a pair (U, A) where the set U is called the universe and has n members denoted xi , while the set A consists of m functions on the universe U . These functions are called the attributes and denoted a j . The attributes are vector-valued functions that may be interpreted, for example, as issues under negotiation by the members of the universe U. An example of an attribute is a function of the form a j : U {-1, 0, 1} . attribute set a set of vectors (signals) lying in metric space that possess prescribed properties. audio science of processing signals that are within the frequency range of hearing, that is,
Narrowband Measurements in Domestic Access Networks
Published in Lars T. Berger, Andreas Schwager, Pascal Pagani, Daniel M. Schneider, MIMO Power Line Communications, 2017
Weilin Liu, Guangbin Chu, Jianqi Li
Narrowband power line channel characteristics in typical underground LV access network in China are evaluated based on measurement results. A three-phase coupling at transformer has very low impedance. This low impedance together with a signal splitting into the three phases may result in considerable signal loss compared to a single-phase coupling. The attenuation has a broad range between 20 and 70 dB. In contrast to BPL, for NB PLC there is not always a clear trend for the attenuation to increase with the frequency and with the distance. On the other side, the noise power decreases with the frequency significantly. Measurements show a reduction of average noise power of 10 kHz noise band-width from a range between 50 and 90 dBμV at 50 kHz to a range between 30 and 60 dBμV at 500 kHz. A considerable difference of noise level between night and day is observable. The noise also exhibits cyclostationary behaviour with a period which corresponds to the half cycle of AC mains. The link quality index (LQI), taking into account both noise and attenuation proved, is a possible measure to compare different channels. An LQI analysis shows that for a given link, there is a strong variation of LQI values along the frequency axis. On average, there is a weak trend in favour of higher frequencies.
Signal Simulators and Emulators
Published in Felix Alberto Farret, Marcelo Godoy Simões, Danilo Iglesias Brandão, Electronic Instrumentation for Distributed Generation and Power Processes, 2017
Felix Alberto Farret, Marcelo Godoy Simões, Danilo Iglesias Brandão
Signal attenuators are widely used in interfaces between instrumentation circuits to match compatible connections and to maximize the signal energy transfer between them. The most common types of attenuators are the resistive divider for low frequencies and the attenuator type π for higher frequencies. To optimize the signal energy transfer, attenuators can be of a symmetrical type having the same impedances Zi and Zo as seen from the input and output terminals, respectively; or otherwise, they are of asymmetric type.
Implementation and evaluation of a front-end ASIC for noise dosimeter applications
Published in International Journal of Electronics, 2020
Daniel Arbet, Martin Kováč, Viera Stopjaková, Miroslav Potočný
The setup for THD measurement also incorporates the input and output amplitude attenuators. Although, the input attenuator (dashed) has not been actually used. Nevertheless, it will be needed for gain measurement, where the minimum signal amplitude generated by the function generator needs to be limited to 100 mV. The output attenuator was formed by two resistors connected in series, each with the value of 68 k, which creates a voltage divider by two in the investigated frequency range. This configuration ensures a non-distorted input signal for the Line-In connector that could be deformed due to the presence of ESD (electro-static discharge) protection diodes at the input of the sound card. It is also important to note that the resistors limit the cut-off frequency of the low-pass filter to a lower value but this has an insignificant effect on the measurement. This is especially true for small values of THD (lower than 2%), where the contribution of higher harmonics can be neglected.
Nickel oxide nanoparticles thin film saturable absorber for 1-micron pulsed all-fibre lasers operation
Published in Journal of Modern Optics, 2018
A. H. H. Al-Masoodi, M. H. M. Ahmed, A. A. Latiff, H. Arof, S. W. Harun
The NiO nanoparticles thin film underwent several characterization processes including X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and non-linear profile measurement. The XRD pattern of the NiO nanostructure is shown in Figure 2(a). There are three peaks that indicate three vibrational modes of the crystalline NiO planes of (1 1 1), (2 0 0) and (2 2 0), located at 37.28°, 43.28° and 62.88°. The observed crystalline planes correspond to the face-centred cubic structure of NiO (26). Figure 2(b) shows the FESEM image of the NiO nanostructures, revealing a high density of morphology with a particle size of less than 50 nm. The non-linear optical absorption properties of the NiO thin film SA was analyzed using the twin-detector method to confirm its saturable absorption profile as shown in Figure 2(c). The input source was a mode-locked fibre laser with a central wavelength of 1560 nm, repetition rate of 1 MHz and pulse width of 2.14 ps. It was connected to a low-dispersion optical amplifier, a variable optical attenuator and then to a 3 dB optical coupler. The output power of the twin-detector was measured using two optical power meters (OPMs). The first OPM was connected to one port of the coupler. The second port of the coupler was connected to the NiO nanoparticles film SA which is then connected to the second OPM. The recorded data of transmissions at various input intensities were fitted using the following equation (27)
Broadband analogue predistortion using a distortion generator based on two-stage RF mixer topology
Published in International Journal of Electronics, 2018
The distortion generator topology proposed in this paper achieves broadband fundamental signal cancellation without using a signal cancellation loop or a resonant circuit. Although an attenuator and a phase shifter are necessary, it does not require time matching for fundamental signal cancellation since there is only one signal path in the distortion generator. The LO signal frequency can be controlled to select the desired IF band. This adds complexity but provides flexibility and enables the technique to work at multiple frequency bands. Also, DC-offset is minimised in the proposed topology since there is no RF/IF self-mixing and frequency doubling. To the best of authors’ knowledge, the proposed distortion generator has not been previously reported in the literature and it is the first time that signal cancellation without using a signal cancellation loop or a resonant circuit has been achieved and reported.