Interlayer region having a signal via for coupling between planar signal lines, where a multi-mode signal propagates through the interlayer region

A high-frequency transmission line, comprising:

• a multilayer substrate including a plurality of dielectric layers stacked on each other;
• signal lines formed on two outer faces of the multilayer substrate;
• a signal via coupling the signal lines formed on the two outer faces;
• at least one ground plane disposed between the plurality of dielectric layers, included in the multilayer substrate, and surrounding a removed region disposed around the signal via;
• and
• a plurality of ground vias penetrating at least one of the plurality of dielectric layers in a layer stacking direction, surrounding the signal via, and electrically coupled to the at least one ground plane,
• wherein,
• an interlayer transmission region is defined by the signal via and the plurality of ground vias, within which a high-frequency signal is transmitted in the layer stacking direction through the interlayer transmission region,
• a via diameter of the signal via is set to a dimension that causes multi mode propagation of the high-frequency signal in the interlayer transmission region, and, while causing the multi mode propagation, the high-frequency signal forms a high-intensity region having a high intensity electric field in a transmission direction and a low-intensity region having a low intensity electric field in the transmission direction,
• at least one of an inter-via distance between the signal via and each of the plurality of ground vias, the via diameter, and a substrate thickness of the multilayer substrate is set to couple the high-frequency signal from the interlayer transmission region, in which the high-intensity region of the multi mode propagation is formed, to the signal lines,
• the at least one ground plane comprising a plurality of ground planes,
• the plurality of dielectric layers comprising three or more dielectric layers,
• the multilayer substrate includes the plurality of dielectric layers and the plurality of ground planes,
• the plurality of ground vias includes interlayer vias penetrating through at least one of the plurality of dielectric layers excluding dielectric layers on which the signal lines are formed, among the three or more of the dielectric layers, and electrically coupled to the plurality of ground planes in contact with a portion of the three or more of the dielectric layers, and
• the interlayer vias each have a dimension that causes a first electric field and a second electric field to mutually cancel, the first electric field comprising a leakage electric field leaking from the interlayer transmission region toward the interlayer vias and traveling between the interlayer vias and the at least one ground plane, and the second electric field comprising a leakage electric field leaking from the interlayer transmission region toward the interlayer vias and entering into the interlayer vias.

A high-frequency transmission line, comprising:

• a multilayer substrate including a plurality of dielectric layers stacked on each other;
• signal lines formed on two outer faces of the multilayer substrate;
• a signal via coupling the signal lines formed on the two outer faces;
• at least one ground plane disposed between the plurality of dielectric layers, included in the multilayer substrate, and surrounding a removed region disposed around the signal via;
• and
• a plurality of ground vias penetrating at least one of the plurality of dielectric layers in a layer stacking direction, surrounding the signal via, and electrically coupled to the at least one ground plane,
• wherein,
• an interlayer transmission region is defined by the signal via and the plurality of ground vias, within which a high-frequency signal is transmitted in the layer stacking direction through the interlayer transmission region,
• a via diameter of the signal via is set to a dimension that causes multi mode propagation of the high-frequency signal in the interlayer transmission region, and, while causing the multi mode propagation, the high-frequency signal forms a high-intensity region having a high intensity electric field in a transmission direction and a low-intensity region having a low intensity electric field in the transmission direction,
• at least one of an inter-via distance between the signal via and each of the plurality of ground vias, the via diameter, and a substrate thickness of the multilayer substrate is set to couple the high-frequency signal from the interlayer transmission region, in which the high-intensity region of the multi mode propagation is formed, to the signal lines,
• the via diameter of the signal via that causes the multi mode propagation of the high-frequency signal through the interlayer transmission region satisfies
• f
• c
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• c
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• where d is an outer diameter of an internal conductor of the interlayer transmission region, D is an inner diameter of an external conductor of the interlayer transmission region, εr is a relative permittivity of a dielectric body disposed between the internal conductor and the external conductor, c is the speed of light, and fc is a critical frequency of a coaxial line which corresponds to the high frequency transmission line, and
• wherein
• the coaxial line corresponds to a quasi coaxial line including the signal via serving as the internal conductor and the plurality of ground vias serving as the external conductor, in the high-frequency transmission line.