Compact LTCC rat-race couplers using multilayered phase-delay and phase-advance T-equivalent sections

In this paper, compact low-temperature co-fired ceramic (LTCC) rat-race couplers are developed using multilayered phase-delay and phase-advance T-equivalent sections. By taking advantage of the multilayered LTCC layout capability, compact 3-D phase-delay and phase-advance T-equivalent sections are designed, and then treated as fundamental elements to construct two types of LTCC rat-race couplers. One type of coupler consists of three phase-delay and a phase-advance sections, whereas the other type coupler is integrated by a phase-delay and three phase-advance sections. At the design frequency 2 GHz, both two types of couplers occupy 3.8×;3.8 mm²circuit sizes, namely areas of 0.025λ₀ ×; 0.025λ₀, where λ₀ is the free-space wavelength. The measured results of the developed couplers agree the simulated results very well. It demonstrates that using multilayered phase-delay and phase-advance T-equivalent sections is an effective approach to miniaturize the circuit size of the rat-race coupler.