Compact RF-filter-modules with lumped elements in LTCC for applications up to 10GHz

In this paper the design and realisation of one diplexer circuit for Tetra/UMTS (Tetra = terrestrialtrunked radio, Germany 380 - 390 MHz (Uplink) 390-400 MHz (Downlink), UMTS = WCDMA, 1.920 MHz - 1.980 MHz (Uplink) 2.110 MHz - 2.170 MHz (downlink)) and one low pass filter for 10 GHz in LTCC materials as independent modules with integrated lumped passives and LGA connections are discussed and the results presented. The target of this work was to achieve a high level of integration using the lowest possible number of LTCC layers and reducing the volume needs of the modules and consequently their production costs. Despite of the excellent integration properties of the LTCC technology, the optimal solution for the diplexer circuit was achieved using a hybrid topology. To achieve compact coils with a wide bandwidth and a high level of integration the modules were realised using fine line structures (width/space 50mum/50mum). Scattering simulations and measurement results are presented and discussed. Finally, through the examples presented in this paper the advantages and the potential of the passive integration in LTCC substrates from low frequencies up to frequencies above 10GHz are clearly shown.