Patent ID: 6953349

Claim:
A multilayer circuit board for high frequency signals comprising: a multilayer wiring board unit including one or more wiring layers, each wiring layer including a transmission line for transmitting high frequency signals; one or more ground layers of a conductive material; one or more insulating layers, each insulating layer being disposed between one of the wiring layers, and one of the ground layers; and a first external electrode on an episurface of the board unit and electrically connected to the transmission line; and a connector unit including a second external electrode electrically connected to the first external electrode; and a fitting portion for retaining on the multilayer wiring board unit one of an external circuit board and an external connector, wherein distance d between the first external electrode and the ground layer closest and perpendicular to the first external electrode is within the range d l ≦d≦d u with respect to values d l and d u determined by the following equations: d l =∈ 0 ∈ r πr 2 ( Z L −ΔZ ) 2 /L e d u =∈ 0 ∈ r πr 2 ( Z L +ΔZ ) 2 /L e where ∈ 0 : electric constant, ∈ r : relative permittivity, r: radius of the first or the second external electrode, whichever is greater, Z L : impedance of the transmission line, ΔZ: impedance tolerance, and L e : sum of inductances of the first and the second external electrodes.