An integrated-circuit module includes a package molding compound layer, a radio-frequency (RF) integrated circuit embedded within the package molding compound layer and having an RF port, a waveguide transition structure embedded within the package molding compound layer, and a redistribution layer. The waveguide transition structure includes a transmission line interface section, a waveguide interface section configured for coupling to a rectangular waveguide housing, and a transformer section configured to provide a mode transition between the transmission line interface section and the waveguide interface section. The redistribution layer includes at least one insulating layer and at least one metallization layer, extending between the RF integrated circuit and the waveguide transition structure across a surface of the package molding compound layer. The first redistribution layer includes an RF transmission line conductively connected between the RF port of the RF integrated circuit and the transmission line interface section of the waveguide transition structure.