Abstract-This paper presents a six-section multi-layer asymmetric 10 dB directional coupler based on offset broadside coupled striplines, using Low Temperature Co-fired Ceramic (LTCC) technology, which operates over a decade bandwidth from 1.8 to 18 GHz. It features high performance transitions between the external signal layer and the buried signal layers, as well as a novel mixed first section to solve the limitations of the coupler access bends. A prototype was manufactured that exhibits a return loss of better than 15 dB, isolation of better than 23 dB and a high coupling accuracy of 10.3±0.6 dB over the 1.8-18 GHz band. This design outperforms previously reported results in terms of bandwidth and shows excellent potential for microwave measurement applications.

In this paper, a design technique to match lumped resistors in the dc to 20-GHz band is presented. This technique makes it possible to implement very wideband matched loads with a return loss that is better than 20 dB. The proposed implementation is simple, low cost, and gives superior performance than previously reported alternatives. The technique was developed to match surface-mount resistors soldered on plastic substrates, and was then successfully applied to match trimmed printed resistors on low-temperature co-fired ceramic substrates.Index Terms-Low-temperature co-fired ceramic (LTCC) circuit, matched load, planar microwave circuit, printed resistors, wideband.

Abstract-A circuit model for vertical transitions between different coplanar waveguide systems using via-holes is presented. The model is directly extracted from the geometry of the transition using closed expressions. Additionally, it can be used to find suitable initial dimensions for the transition in a circuit simulator, thereby greatly reducing the effort spent on subsequent electromagnetic simulations. To test the validity of the developed model, it is applied to a variety of situations involving a wide range of stack heights, dielectric constants, and transmission line geometry values. These situations cover most of the relevant broadband vertical transitions used in practical PCB and LTCC designs. Comparative analysis of the circuit model and electromagnetic simulations yields good agreement in all analyzed situations. Experimental assessment of the model is also provided for some of the transitions that were built and characterized in a back-toback configuration.

This article presents a simple topology for the implementation of crosscouplings between nonadjacent resonators in interdigital stripline filters. This topology affords the inclusion of transmission zeros maintaining a cross-sectional structure similar to that of a stripline. Therefore, the manufacturing cost is very close to an all-pole prototype. Two design strategies for the coupling structure are discussed: one of them achieving filters with enhanced performance. Both strategies have been assessed implementing prototypes in low-temperature cofired ceramic (LTCC) technology. The fabricated filters exhibit operating frequencies at 5775 MHz and 8000 MHz with 2.6% and 3.75% pass-band fractional bandwidths, respectively, and up to 60 dB IL in the rejection band. V C 2014 Wiley Periodicals, Inc. Int J RF and Microwave CAE 24:560-570, 2014.