Mismatch loss

Abstract: The problem of the minimum loss in relation to the singing point is investigated for generalized transmission systems that must be stable for any combination of passive terminating impedances. It is concluded that the loss may approach zero db only in those cases where the image impedances seen at the ends of the system are purely resistive. Moreover, in such cases, the method of overcoming the transmission loss, whether by conventional repeaters or by series and shunt negative impedance loading, or otherwise, is quite immaterial to the external behavior of the system as long as the image impedances are not changed. The use of impedance-correcting networks provides one means of insuring that phase of the image impedance of the over-all system approaches zero. General relations are derived which connect the image impedance and the image gain of an active system with its over-all performance properties.

Abstract: In the world, energy needs of people are met by fossil fuels. However, fossil fuels are getting depleted day by day and using of them causes negative effect on the environment. Moreover, energy demand of the world has increased in recent years. Hence, in order to meet the energy demand, especially solar or photovoltaic energy is widely used among the renewable energy sources. Photovoltaic cell directly convert solar energy into electricity. However, efficiency of photovoltaic cell is negatively affected by partial shading. Partial shading generally occurs on photovoltaic systems due to passing cloud, neighboring building, tree, etc. As a result of partial shading, produced power from photovoltaic system is less than the expected power value. One of the solutions of this problem is photovoltaic array configurations scheme. In this study, five different photovoltaic array configuration schemes: Series, Series-Parallel, Total-Cross-Tied, Bridged-Linked, and Honey-Comb, are carried out using 6 × 6 photovoltaic array under six different shading cases. Simulations of all shading cases are implemented using MATLAB/Simulink. In general, the obtained maximum power results under all partial shading cases show that Total-Cross-Tied configuration has the best performance according to other configurations. Furthermore, the obtained results have been compared in terms of shading loss, mismatch loss, and fill factor.

Abstract: An impedance matching arrangement is suitable for use with a frequency hopping radio communications system which is operable over a wide frequency band, so as to match the operating impedance of the antenna at each of the frequencies used. As the frequency of the radio system hops from one frequency to another, a note of any impedance mismatch is noted and data derived therefrom is stored for future use when that frequency is next selected so as to reduce any impedance mismatch.

Abstract: As per energy efficiency of a photovoltaic (PV) system is concerned, partial shading is an important issue. Under partial shading condition, the modules of a PV array receive different levels of solar irradiation, so the power generation of a PV system decreases. The power–voltage characteristic of a partially shaded PV array contains multiple local maxima, and the global maximum power point is one of them. The losses in a PV array depend on the shading pattern and the physical location of shaded modules. This paper presents the Futoshiki puzzle pattern for the arrangement of the modules of a PV array under partial shading condition, ensuring the enhancement of the power generation with respect to totally crossed tired (TCT) structure. In this method, the physical locations of modules in a TCT structure PV array are rearranged without changing the electrical connection of the modules. A comparison between the power generation in TCT and Futoshiki puzzle pattern configuration is presented. It is demonstrated that the power generated by a PV array in the Futoshiki configuration method is enhanced, and mismatch loss (ML) is minimized under different shading patterns by theoretical, simulation, and experimental results.

Abstract: A communication system for small-scale local area networks using the power transmission line is discussed. With this application in mind and noise power spectrum of a power line at 10 kHz-100 MHz and the impedance characteristics and transmission loss of a power line in the high frequency band (10 kHz-20 MHz) have been measured. Both narrowband and wideband data transmission are considered. The transmission loss of the power line increases with frequency, whereas the intensity of the noise power spectrum decreases rapidly. This means that power line communication by a single-sideband system is possible using a wide frequency band up to 100 MHz. However, the noise, impedance, and transmission characteristics vary greatly with frequency, so special considerations such as line impedance stabilization networks and other techniques are necessary. >