Abstract: An electronic device may have an antenna that conveys radio-frequency signals at frequencies greater than 10 GHz. The antenna may be embedded in a substrate. The substrate may have routing layers, first antenna layers on the routing layers, second antenna layers on the first antenna layers, and a third antenna layers on the second antenna layers. The antenna may include first traces on the first antenna layers, second traces on the second antenna layers, and third traces on the third antenna layers. The first antenna layers may have a first bulk dielectric permittivity. The second layers may have a second bulk dielectric permittivity. The third layers may have a third bulk dielectric permittivity. At least one of the first, second, and third bulk dielectric permittivities may be different from the others. This may differentially load the antenna across the antenna layers, thereby broadening the bandwidth of the antenna.

Abstract: An electronic device may have an antenna that conveys radio-frequency signals at frequencies greater than 10 GHz. The antenna may be embedded in a substrate. The substrate may have routing layers, first antenna layers on the routing layers, second antenna layers on the first antenna layers, and a third antenna layers on the second antenna layers. The antenna may include first traces on the first antenna layers, second traces on the second antenna layers, and third traces on the third antenna layers. The first antenna layers may have a first bulk dielectric permittivity. The second layers may have a second bulk dielectric permittivity. The third layers may have a third bulk dielectric permittivity. At least one of the first, second, and third bulk dielectric permittivities may be different from the others. This may differentially load the antenna across the antenna layers, thereby broadening the bandwidth of the antenna.