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The phase difference between the two output ports of a hybrid coupler should be 0°, 90°, or 180° depending on the type used. However, like amplitude balance, the phase difference is sensitive to the input frequency and typically will vary a few degrees. [12]
An alternative which allows the Butler matrix to be implemented entirely in printed circuit form, and thus more economically, is a crossover in the form of a branch-line coupler. [13] The crossover coupler is equivalent to two 90° hybrid couplers connected in cascade. This will add an additional 90° phase shift to the lines being crossed, but ...
With directional couplers, directivity is a measure of the difference in dB of the power output at a coupled port, when power is transmitted in the desired direction, to the power output at the same coupled port when the same amount of power is transmitted in the opposite direction. [15]
Rat-race couplers are used to sum two in-phase combined signals with essentially no loss or to equally split an input signal with no resultant phase difference between its outputs. It is also possible to configure the coupler as a 180 degree phase-shifted output divider or to sum two 180 degree phase-shifted combined signals with almost no loss.
The advantage of using a directional coupler rather than a simple summing circuit is that the directional coupler provides isolation between the two generators. As with the component testing, another signal being injected into the output of a signal generator can cause intermodulation distortion within the generator.
A magic tee (or magic T or hybrid tee) is a hybrid or 3 dB coupler used in microwave systems. [1] It is an alternative to the rat-race coupler . In contrast to the rat-race, the three-dimensional structure of the magic tee makes it less readily constructed in planar technologies such as microstrip or stripline .
No loss occurs when the signals at ports 2 and 3 are in phase and have equal magnitude. In case of noise input to ports 2 and 3, the noise level at port 1 does not increase, half of the noise power is dissipated in the resistor. By cascading, the input power might be divided to any -number of outputs.
A directional SWR meter measures the magnitude of the forward and reflected waves by sensing each one individually, with directional couplers. A calculation then produces the SWR. A simple directional SWR meter. Referring to the above diagram, the transmitter (TX) and antenna (ANT) terminals connect via an internal transmission line.