This application relates to a device for signal transmission (e.g., radio frequency transmission) and a method for forming the device. For example, the method includes: depositing an insulating layer that includes polybenzobisoxazole (PBO) on a carrier; forming a backside layer including polyimide (PI) over the adhesive layer; forming a die-attach film (DAF) over the backside layer; forming one or more through-insulator via (TIV)-wall structures and one or more TIV-grating structures on the second backside layer, placing a die, such as a radio frequency (RF) integrated circuit (IC) die, on the DAF; encapsulating the die, the one or more TIV-wall structures, and the one or more TIV-grating structures, with a molding compound to form an antenna package including one or more antenna regions; and forming a redistribution layer (RDL) structure on the encapsulated package. The RDL structure can include one or more antenna structures coupled to the die. Each of the one or more antenna structures can be positioned over the one or more antenna regions.