In complementary metal-oxide-semiconductor (CMOS) radio frequency integrated circuits (RFIC), a balun structure is an important electrical structure that is mainly used to achieve a conversion between an unbalanced signal and a balanced signal.
Inductor is one of the core components of the balun structure, and the performance parameters of the inductor are directly related to the performance of the balun structure. The inductors in the integrated circuits are mainly planar inductors, such as a planar spiral inductor. The planar spiral inductor can be formed by wounding a metal wire on the surfaces of a substrate or a dielectric layer. Compared with a conventional wire inductor, the planar inductor may have many advantages such as low cost, easy integration, low noise, low power consumption, etc. More importantly, the planar inductor can be compatible with existing integrated circuit processes.
Inductor quality factor Q and insertion loss (IL) are two main factors that affect the performance of the balun structure. The inductor quality factor Q and the insertion loss are related to the performance of the radio frequency (RF) front-end circuit in the balanced mixer, and the amplifier-related limit noise, power loss, etc.
In order to improve the inductor quality factor Q and reduce the insertion loss, an area of the coil in the balun structure can be generally large, which results in a large area of the wafer occupied by the coil in the balun structure.
Accordingly, the disclosed balun structure is directed to solve one or more problems set forth above and other problems.