Highly integrated millimeter-wave passive components using 3-D LTCC system-on-package (SOP) technology

In this paper, we demonstrate the development of advanced three-dimensional (3-D) low-temperature co-fired ceramic (LTCC) system-on-package (SOP) passive components for compact low-cost millimeter-wave wireless front-end modules. Numerous miniaturized easy-to-design passive circuits that can be used as critical building blocks for millimeter-wave SOP modules have hereby been realized with high-performance and high-integration potential. One miniaturized slotted-patch resonator has been designed by the optimal use of vertical coupling mechanism and transverse cuts and has been utilized to realize compact duplexers (39.8/59 GHz) and three- and five-pole bandpass filters by the novel 3-D (vertical and parallel) deployment of single-mode patch resonators. Measured results agree very well with the simulated data. One multiplexing filter, called the directional channel-separation filter, that can also be used in mixer applications shows insertion loss of <3 dB over the bandpass frequency band and a rejection ∼25 dB at around 38.5 GHz over the band-rejection section. LTCC fabrication limitations have been overcome by using vertical coupling mechanisms to satisfy millimeter-wave design requirements. Lastly, a double-fed cross-shaped microstrip antenna has been designed for the purpose of doubling the data throughput by means of a dual-polarized wireless channel, covering the band between 59-64 GHz. This antenna can be easily integrated into a wireless millimeter-wave link system.