| 摘要 |
A compact four-port two branch coupler preferably constructed in stripline or microstrip media having an input port and a pair of output ports. The equivalent admittance of a coupler has a real part (conductance) and imaginary part (susceptance), and known design techniques require the branch line electrical length theta to be pi /2 or 90 DEG , so that the device is properly matched. However, to reduce the physical line lengths at a predetermined operating frequency in accordance with the invention the electrical length theta is chosen at a lower value of, for example, pi /4 or 45 DEG thereby reducing the line lengths of the branches making the device more compact. This choice now creates an inductive mismatch in the equivalent admittance which is easily compensated for by a capacitance at each junction in order to make the total susceptance zero so that the device is matched for theta = pi /4. This is accomplished quite effectively with the capacitive sections being conveniently located in the central open area formed between the four strip networks defining the coupler.
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