This paper presents the development of RF System-on-Package (SOP) architectures for compact and low cost wireless radio front-end systems. A novel 3D integration approach for SOP-based solutions for wireless communication applications is proposed and utilized for the implementation of a C band Wireless LAN (WLAN) RF front-end module by means of stacking LTCC substrates using μBGA technology. LTCC designs of high-performance multilayer embedded bandpass filters and novel stacked cavity-backed patch antennas are also reported. In addition, the fabrication of very high Q-factor inductors and embedded filter in organic substrates demonstrate the satisfactory performance of multilayer organic packages. The well known full-wave numerical techniques of FDTD and MRTD are used for the modeling of adjacent lines crosstalk, of the Q-factor of embedded passives and for the accurate simulation of MEMS structures.