Ruben Perrone

Comparison of High-Resolution Patterning Technologies for LTCC Microwave Circuits

Low-temperature co-fired ceramic (LTCC) are widely acknowledged for wide-band and microwave circuits. Within the project consortium KERAMIS, implementation of higher functionality in LTCC substrates is being investigated. Among the applications considered are a 4 × 4 switch matrix [1], voltage-controlled oscillators [2], and amplifiers for multimedia satellite communications working in Ka-band. In order to add more functionality (e.g., filters, couplers) in LTCC, current patterning limits of line width and line separation need to be extended. Four different technologies were considered for higher resolution: a) fine-line printing technology with special screens, b) photo-imageable pastes, c) etching of thick-film conductors (co- and post-fired), and d) thin films on LTCC. Evaluation of patterning technologies is based on a test coupon that was designed and manufactured by the consortium members. The artwork contains lines, line transitions, ring resonators (microstrip and stripline), edge-coupled filters, DC blocking structures, and various lines for DC resistance testing. The smallest gap definition is 50 μm. Two substrate materials, Du Pont tapes 951 and 943, are included in the study. In addition to the main frequency band of interest in the project (17-22 GHz), these structures have been characterized up to 50 GHz. Electrical results are correlated to physical measurements of the structures (line width, spaces, and tolerances) and are evaluated with respect to performance, manufacturability, and yield. Results show excellent performance for screen-printed structures and demonstrated the importance of mask tuning to achieve optimum resolution (under etching etc.).

Progress in the Integration of planar and 3D Coils on LTCC by using photoimageable Inks

This paper presents some results of our investigations in the integration of coils in LTCC using the Fodel® Technology as line patterning technology. Planar as well as 3-D inductors were simulated, manufactured, measured and modeled. The structures were manufactured with different shapes, a line width from 30 μm to 70 μm, a space between turns from 100 μm and 200 μm and diameters of inner turns from 0.5 mm to 2 mm. The smallest and most critical inductors (0.5 mm diameter) were manufactured with vias, whose diameter were about 60 μm. The manufacturing of smaller coils was possible due to the increased resolution of Fodel® thick-film inks also in inner layers in combination with micro vias, which were produced with a multifunctional Laser. Combining these technologies with buried cavities and a symmetric turn arrangement we obtained inductors that can be used in a wider range of frequencies (up to 10 GHz).

Tunable Dual-Band Microwave Devices based on a Combination of Left/Right-Handed Transmission Lines

Metamaterial transmission lines can be realized as a combination of transmission line sections with positive and negative dispersion. Such lines, which are also known as right- and left-handed transmission lines, exhibit different dispersion characteristics. Compared to homogeneous networks, the use of cascaded line sections gives additional degrees of freedom for improving the performance of microwave devices. For the design process, LC-equivalents of the right- and left-handed transmission line sections are used. This facilitates the consideration of tunable capacitors, e.g., varactor diodes, to provide frequency tuning of the devices. At the same time, the geometrical dimensions of the devices can be drastically reduced. This paper presents the results of simulation and experimental investigation of a miniature rat-race-ring and a dual-band filter free of spurious response, both manufactured as fully-integrated ceramic multilayer modules based on Low-Temperature Co-fired Ceramics. The design of tunable versions of these devices is also discussed.

Tunable microwave devices based on left/right-handed transmission line sections in multilayer implementation

Metamaterial transmission lines can be realized as a combination of right- and left-handed transmission line (TL) sections exhibiting positive and negative dispersion. This approach gives additional degrees of freedom for improving the performance of microwave devices. Artificial right- and left-handed sections, which are based on lumped-element unit cells consisting of inductance and capacitances (LC-cells), are used. This makes it possible to decrease dimensions of the devices drastically. Furthermore, using variable capacitors in LC-cells allows designing tunable devices. This paper presents the results of design, numerical simulation, and experimental investigation of a tunable rat-race ring and free-of-spurious response dual-band filter manufactured as integrated ceramic multilayer circuits based on low-temperature co-fired ceramics. Commercial semiconductor varactors have been used as tunable components.

180° Power Dividers Using Metamaterial Transmission Lines

Application of metamaterial left-handed transmission lines to design 180deg power dividers is considered. Design of microstrip and coplanar miniaturized rat-race rings based on artificial left-handed and right-handed transmission line sections is presented. The devices have been implemented as quasi-lumped-element multilayer structures on low-temperature co-fired ceramics. Novel broadband Wilkinson-type 180deg power dividers using metamaterial left-handed transmission lines are proposed.

High functional density low-temperature co-fired ceramic modules for satellite communications

For satellite communication downlinks in the Ku/K-band we have integrated active semiconductor switching circuits with high-resolution passive components into a ceramic module for a 4 /spl times/ 4 single-pole multi-throw reconfigurable switch matrix. The modular design includes different types of transmission lines, transitions, impedance matching circuits, and biasing and decoupling networks enabling digitally controlled reconfiguration. As a first step towards a complete, hermetically sealed, package, we have designed and characterised sub-modules incorporating individual active and passive components, to identify the limits of the technology. The scattering parameters measured for a stack of eleven layers, with the top layer and four embedded layers containing RF signal lines and minimum line widths of 40 /spl mu/m, prove the principle-of-operation. The performance was found to be limited, at present, by the switch-ICs and their first-level interconnections, and can be still improved significantly.

Multi-band and tunable multi-band microwave resonators and filters based on cascaded left/right-handed transmission line sections

Design of microwave devices based on a combination of traditional right-handed transmission line sections with positive dispersion and metamaterial left-handed transmission line sections with negative dispersion is considered. Compared to homogeneous transmission lines, the use of cascaded line sections gives additional degrees of freedom for the design of microwave devices with enlarged functionality and unique performance. Artificial right- and left-handed transmission lines based on lumped-element equivalent cells help to minimize the dimensions of microwave devices. For filters, a combination of cascaded right- and left-handed transmission lines can be applied advantageously, to control the position and the widths of the individual pass-bands and the parasitic response of higher harmonics. This paper describes the theoretical approach to the design of multi-band resonators and filters with highly suppressed response of higher harmonics. Selected devices were manufactured as three-dimensional ceramic multilayer modules based on low-temperature co-fired ceramic technology. The results of numerical simulation and experimental investigation of these devices are compared. Furthermore, the employment of variable capacitors in single cells of artificial transmission lines provides frequency tuning of the devices. The design of tunable dual-band filters is discussed, and the experimental results are presented.

Novel Wilkinson-Type Power Dividers Based on Metamaterial Transmission Lines

This paper focuses on applications of the metamaterial left-handed transmission lines to the design of novel Wilkinson-type power dividers. Novel configurations of broadband 180deg Wilkinson power dividers suitable for practical implementation are proposed. A concept of designing dual-band Wilkinson power dividers based on a combination of right-handed and left-handed transmission line sections is considered as well. A band broadening technique for the dual-band Wilkinson power dividers is discussed.

Electrical Properties of Low Temperature Cofired Ceramics with Integrated Bulk Metals

Constrained sintering allows the cofired integration of bulk metals in LTCC (low temperature cofired ceramics) instead of paste prints. A difficulty of such an integration is the application of the metallic structures on the sensitive unfired ceramic foils. The paper shows different techniques for solving this problem. Higher possible resolution and more precise edges are the advantages of bulk metal structures. Other results are improved electrical properties. Different kinds of conductor designs were used to figure out the electrical features in the fields of radio frequencies and high power applications. The reduction of transmission losses in triplate lines up to frequencies of 45 GHz will be shown and discussed. Coils for powers supplies were investigated and measured at lower frequencies. Higher specific conductivity and thickness of bulk lines allow the realization of inductors with higher quality factor and lower resistance. The advantages of the new cofiring technology for LTCC and the potential for different applications will be discussed.