On‐Chip Realization of Synthesized Transmission Lines Using IPD Processes

System‐on‐chip (SoC) and system‐inpackage (SiP) technologies have become the core business in communication industries over the past decade. When the operating frequency goes high, one may experience difficulties in realizing synthesized transmission lines using PCB processes due to the limitation of line resolution. To alleviate the problem, the integrated passive device (IPD) process, having received considerable attention in the SiP integration, is applied to fulfill on‐chip synthesized transmission lines and hence circuit miniaturization at higher frequencies. In this chapter, a variety of synthesized transmission lines using the IPD technology are introduced to realize on‐chip microwave/millimeter‐wave passive components. On‐chip synthesized lines, generally consisting of quasi‐lumped meander/spiral inductors, metal‐insulator‐metal (MIM) capacitors, and open stubs, feature an extremely compact size with impressive slow wave factor. The concept of multi‐mode operation is also fulfilled by quasi‐lumped components on the IPD substrate. Their applications to the multiplexer, antenna decoupling network, and liquid detector are also discussed.