Patent ID: 6856210

Claim:
A high-frequency multilayer circuit substrate comprising: at least three circuit layers, an inner circuit layer of which includes a ground conductor; a via hole penetrating the plurality of circuit layers to be connected to each other; a via hole metal pad provided around the via hole; a planar impedance matching circuit connected to the via hole through the via hole metal pad; and a microstrip line being a signal transmission line, formed in at least one of the circuit layers other than the inner circuit layer, connected to the planar impedance matching circuit, wherein a characteristic impedance of a via hole connecting portion formed by the via hole, the via hole metal pad and the planar impedance matching circuit matches a characteristic impedance of the signal transmission line, the planar impedance matching circuit includes an impedance matching microstrip line, one end of which is connected to the via hole through the via hole metal pad and other end of which is directly connected to the microstrip line being the signal transmission line, the via hole metal pad, the planar impedance matching circuit and the microstrip line being the signal transmission line are located on the same circuit layer.