Branch-Line Couplers With Arbitrary Coupling Value Through the Electrical Length Variation With Fixed Line Impedances

A new method is presented to obtain arbitrary coupling levels of the branch-line couplers through the simple modification of the 3-dB coupler. It is shown that the coupling of the conventional 3-dB branch-line coupler can be adjusted to arbitrary values by varying the electrical length of the branches without changing the impedances. A very wide range of coupling values can easily be obtained using the same line impedances as the conventional 3-dB couplers based on the proposed method.