Patent ID: 8203398

Claim:
A directional coupler having a coupling factor in the forward direction determined from the equation C f =C f ·e jφ Cf , a coupling factor in the reverse direction determined from the equation C r =C r ·e jφ Cr , an isolation in the forward direction determined from the equation I f =I f ·e jφ If , and an isolation in the reverse direction determined from the equation I r =I r ·e jφ Ir , the directional coupler comprising: a main line; a coupling line; and a coupling variance connected to the main line and the coupling line; wherein the coupling variance is adjustable to meet at least one condition from among the group consisting of: (1) the absolute value of Δφ=φ Cr +φ Cf −(φ Ir +φ If ) being less than or equal to 20°, K = C f C r * I r I f ( 2 ) is less than or equal to 1.6, and (3) Cf=Cr and If=Ir.