Proceedings of the 48th European Microwave Conference Suppression of Acoustic Resonances in Fully-Printed, BST Thick Film Varactors Utilizing Double MIM Structures

Low loss, fully-printed, ferroelectric varactors for high-power impedance matching at low ISM band frequency

“…The presented acoustic suppression technique is based on the work of [10,11] and presented in detail in [9]. As a fundamental structure for the theory, a layered double MIM setup is assumed, see Fig.…”

“…Thereby, a widely homogeneous depositioning pattern is achieved. In regard to the design process, main focus is laid upon increased creepage distances, higher electrical strength and durability of the varactor by increasing tolerances and layer thicknesses in comparison to the design process presented in [9].…”

“…Each cell features an electrode overlap area of 1.1 mm × 5.5 mm, resulting in a theoretical cell capacity of 300 pF with ε r = 230 and a layer thickness of 20 µm. The difference of the high-power optimized design compared to the cells presented in [9] are the increased size of each cell to obtain a reasonable overall capacitance value of the structure and increased tolerances from 50 to 250 µm. of each layer to increase creepage.…”

“…Subsequently, the middle electrode and two more layers of BST are printed and dried at 80 ° C. Eventually, the top electrode is printed and the whole structure is sintered at 850 ° C for 10 min. Considering the manufacturing process presented in [9] and its effects on the suppression of acoustic resonances based on interference, the homogeneously processed case is applied to all four BST layers, resulting in equal material properties in the top and bottom BST layers. A SEM cross-sectional image of the homogeneously co-sintered double MIM structure is depicted in Fig.…”

“…A superimposed RF voltage latches onto the induced dipole moment, resulting in mechanical/acoustical vibrations, which reduce the varactors Q -factor and therefore its power-handling capabilities [7,8]. In this paper, a fully-printed thick film varactor is demonstrated in a matching circuit and input power levels of up to 1 kW, with an implemented interference-based acoustic suppression technique, described and verified in [9]. The suppression mechanism utilizes novel fully-printed doublemetal–insulator–metal (MIM) varactor cells.…”