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Practical impedance-matching devices will generally provide best results over a specified frequency band. The concept of impedance matching is widespread in electrical engineering, but is relevant in other applications in which a form of energy, not necessarily electrical, is transferred between a source and a load, such as in acoustics or optics.
Another application is the design of impedance matching networks. Impedance matching at a single frequency requires only a trivial network—usually one component. Impedance matching over a wide band, however, requires a more complex network, even in the case that the source and load resistances do not vary with frequency.
An L-network is the simplest circuit that will achieve the desired transformation; for any one given antenna and frequency, once a circuit is selected from the eight possible configurations (of which six are shown above) only one set of component values will match the in impedance to the out impedance. In contrast, the circuits described below ...
The Opcode consists of 2 bits. There are two possible opcodes, read '10' or write '01'. PA5. 5 bits, PHY address. RA5. The Register Address field indicates the register to be written to or read from. It is 5 bits long. TA. The turn-around field is 2 bits long. When data is being written to the PHY, the MAC writes '10' to the MDIO line.
This impedance is sometimes called the network's characteristic impedance, a term usually reserved for transmission lines. [10] The model for a transmission line is an infinite chain of L-sections with infinitesimally small components. A transmission line characteristic impedance is thus the limiting case of a ladder network iterative impedance.
Equivalent unbalanced and balanced networks. The impedance of the series elements in the balanced version is half the corresponding impedance of the unbalanced version. Fig. 3. To be balanced, a network must have the same impedance in each "leg" of the circuit. A 3-terminal network can also be used as a 2-port.
Network theorem governs that a divider cannot satisfy all three conditions (being matched, reciprocal and loss-less) at the same time. Wilkinson divider satisfies the first two (matched and reciprocal), and cannot satisfy the last one (being loss-less). Hence, there is some loss occurring in the network.
The input impedance of an infinite line is equal to the characteristic impedance since the transmitted wave is never reflected back from the end. Equivalently: The characteristic impedance of a line is that impedance which, when terminating an arbitrary length of line at its output, produces an input impedance of equal value. This is so because ...