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Techniques of impedance matching include transformers, adjustable networks of lumped resistance, capacitance and inductance, or properly proportioned transmission lines. Practical impedance-matching devices will generally provide best results over a specified frequency band .
In the case of purely resistive circuits, the two concepts are identical. Physically realizable sources and loads are not usually purely resistive, having some inductive or capacitive components, and so practical applications of this theorem, under the name of complex conjugate impedance matching, do, in fact, exist.
Impedances with non-negative resistive components will appear inside a circle with unit radius; the origin will correspond to the reference impedance, Z 0. The Smith chart is plotted on the complex reflection coefficient plane in two dimensions and may be scaled in normalised impedance (the most common), normalised admittance or both, using ...
In all of the circuits given below it is assumed that the generator and load impedances are purely resistive (though not necessarily equal) and that the attenuator circuit is required to perfectly match to these. The symbols used for these impedances are; the impedance of the generator
An antenna tuner, a matchbox, transmatch, antenna tuning unit (ATU), antenna coupler, or feedline coupler is a device connected between a radio transmitter or receiver and its antenna to improve power transfer between them by matching the impedance of the radio to the antenna's feedline.
Passive, resistive pads and attenuators are bidirectional two-ports, but in this section they will be treated as unidirectional. Z S = the output impedance of the source. Z Load = the input impedance of the load. Z in = the impedance seen looking into the input port when Z Load is connected to the output port.
The picture shows the impedances seen on the PCB nets during a read cycle. During reads, it is recommended that the DRAM be configured for an effective drive impedance of RZQ/7 or 34 Ω (assuming the RZQ resistor is 240 Ω). The on-die termination (ODT) within the DRAM controller will have an effective Thevenin impedance of 45 Ω.
This is not the same as the actual impedance of the load since the reactive part of the load impedance will be subject to impedance transformer action and the resistive part. Matching stubs can be made adjustable so that matching can be corrected on test. [3] A single stub will only achieve a perfect match at one specific frequency.
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