| 摘要 |
PURPOSE:To realize easily a directional coupler featuring a similar degree of connection to the conventional one along with a wide gap width by using the anisotropic dielectric substrate showing a large dielectric constant within the plane parallel to the substrate surface. CONSTITUTION:For substrate 21, the dielectric constants are epsilon1 and epsilon2 with the X-Y plane and in the z direction each (epsilon1>epsilon2), and distribution coupling lines 23 and 24 are provided on the upper surface along with earth conductor 22 provided on the bottom surface. With the excitations in the even and odd modes, capacities CE=CP+CF+CGE and CO=CP+CF+CGO are caused in accordance with the mode for conductor 31, and the characteristic impedance is adversely proportional to the square root. The inter-line capacity CGO is large since constant epsilon1 is large, and capacity CP to earth conductor 33 plus line end capacities CF and CGE are also depending on constant epsilon2. Thus capacity Ce depends almost on epsilon2, and CO depends on both epsilon2 and epsilon1. Accordingly, if epsilon1>epsilon2 is satisfied, the odd mode impedance can be decreased virtually regardless of the even mode impedance, increasing the coupling coefficient. |
