Versatile microwave dual-band tunable resonator

The authors present a versatile structure of a frequency-independent tunable dual-band resonator, which is able to surpass the barrier of the resonant frequency ratio f ₂/f ₁=2 between the first two resonant frequencies. A complete description and a designing method for different types of tunable dual-band resonators are presented. The analysis begins with the simplest cases to properly understand the behaviour of the involved networks. Different implementations are tested and validated through simulations and measurements.