Abstract: A multilayer board includes a multilayer body including a first radiation conductor layer, a ground conductor layer, a first wiring layer, and a second wiring layer. The first wiring layer is electrically connected to a first radiation conductor layer at a first power supply point positioned closest to a first straight line in a first outer edge and intersects but is not orthogonal to the first straight line in a view along a Z-axis direction. The second wiring layer is electrically connected to the first radiation conductor layer at a second power supply point positioned closest to a second straight line in the first outer edge and intersects but is not orthogonal to the second straight line in a view along the Z-axis direction.

Abstract: A maximum width of a second connection portion in a line width direction is smaller than a maximum width of a first connection portion in the line width direction. A first intermediate portion includes a first thick-line portion of which the width is greater than that of a transmission line portion in the line width direction. A second intermediate portion includes a second thick-line portion of which the width is greater than that of a transmission line portion in the line width direction. The first thick-line portion and the second thick-line portion adjoin the transmission line portion.

Abstract: A multilayer body has a structure including insulating layers stacked on each other in an up-down direction. A first conductive layer is on a top main surface of one of the insulating layers. A first signal is transmitted through the first conductive layer. A second conductive layer is on a same insulating layer that the first conductive layer is on. The second conductive layer is on a same main surface as the top main surface or the bottom main surface of the insulating layer on which the first conductive layer is located. A second signal having a higher frequency than the first signal is transmitted through the second conductive layer. A top conductive layer is above the second conductive layer. A thickness of the second conductive layer in the up-down direction is smaller than that of the first conductive layer in the up-down direction.

Abstract: A multilayer substrate includes layers stacked on each other in an up-down direction of a multilayer body. The layers include a first spacer, a first ground conductive layer above the first spacer, and a signal conductive layer that overlaps the first ground conductive layer and is located below the first spacer. First through-holes pass through the first spacer and are arranged along a first direction. A distance between centroids of first through-holes adjacent to each other in the first direction is uniform or substantially uniform. Sets of first through-holes are provided in the first spacer. Sets of first through-holes are arranged along a second direction. A distance between centroids of first through-holes adjacent to each other in the second direction is uniform or substantially uniform. At least one first through-hole is a first hollow through-hole overlapping the signal conductive layer.

Abstract: In a transmission line, a hollow portion overlaps a first ground conductor layer in an up-down direction. In a first orthogonal direction, the hollow portion includes a first portion extending in a second orthogonal direction of a signal conductor layer. In the first portion, a portion at which a width of the first portion in the second orthogonal direction has a first portion maximum width value is a first portion maximum width portion. A portion at which the width of the first portion in the second orthogonal direction has a first portion minimum width value is a first portion minimum width portion. A portion at which the width of the first portion in the second orthogonal direction has a first portion intermediate width value is a first portion intermediate width portion located between the first portion maximum width portion and the first portion minimum width portion in the front-back direction.

Abstract: A circuit board includes a multilayer body including a main surface, a mounted conductor, and a signal conductor at an intermediate position in the lamination direction of the multilayer body, and a ground conductor on the main surface. The multilayer body includes a connection portion including a portion overlapping the mounted conductor and overlapping an external board joined via a conductive joint material through use of the mounted conductor, and a circuit portion. A first region, which is the region of a circuit portion of the ground conductor, includes opening holes and a second region, which is the region of a connection portion of the ground conductor, includes opening holes. The ratio of the opening area of the opening holes to that of the second region is larger than the ratio of the opening area of the opening holes to that of the first region.