J. Trabert

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.).

Ceramic Microwave Circuits for Satellite Communication

KERAMIS is the acronym of a German research and development project funded by the German Space Agency (DLR) and the Federal Ministry of Economics and Technology (BMWI). The consortium is developing an RF circuit technology for Ka band multimedia satellite applications. A set of modules has been designed, manufactured, and tested by the partners of the consortium. The goal of this effort is to qualify the KERAMIS technology for space applications and to participate in an on-orbit-verification (OOV) program of the DLR. The launch of the technology verification satellite (TET) is scheduled for late 2010. This paper will give an overview of innovative circuit and module designs as well as the assembly, integration, and test results of the project. The authors will present a modular circuit concept for state-of-the-art transmitters and receivers in space at around 20 GHz. Selected modules are a 4 × 4 switch matrix, two synthesizers, and other RF modules. All circuits are based on multilayer ceramic (LTCC) incl...

60 GHz patch antennas in LTCC technology for high data-rate communication systems

We have developed rectangular patch antennas with single-ended and balanced feed ports, respectively, for use in high data-rate millimetre wave transmission systems. The antennas were designed for the unlicensed ISM-band at 60 GHz, and fabricated in ceramic multilayer technology employing high dielectric-constant materials. For the experimental characterisation of the balanced layout with a coplanar wafer prober, a wide-band balun was designed, which transforms a coplanar waveguide into a coplanar stripline. For the characterisation of the single-ended structures, a transition to microstrip line was used instead. For both types of antennas, measured S-parameters are presented and analysed.

On-Orbit Verification of a 4×4 switch matrix for space applications based on the low temperature co-fired ceramics technology

Abstract We have developed a compact, high-performance, mechanically robust reconfigurable microwave switch matrix as well as peripheral components such as diode driver, voltage controlled oscillator, and power detector modules for satellite applications using the low temperature co-fired ceramics technology (LTCC) and hybrid integration of integrated circuits. In order to verify the technology for space applications, we combined these components to build a system that enables automated verification of the switch matrix in space, accounting for power consumption, mass, overall geometrical dimensions, and mechanical robustness. The system passed a full space qualification. During a one year On-Orbit-Verification (OOV) mission aboard the German test satellite TET-1 (technology evaluation carrier) launched on July 22, 2012, the correct operation and reliability of the entire switch matrix system and thereby the used technology will be demonstrated.

High-power filters for switched-mode power amplifier systems

This paper presents the design and experimental characterisation of a coaxial comb-line band-pass filter for a switched-mode power amplifier (class-S), for an operating frequency of 450 MHz. The class-S amplifier architecture is laid out for very efficient amplification and high-power operation. Both requirements present challenges for the design of the reconstruction filter terminating the final stage. According to measurement results, an initially developed filter provided a bandwidth of 26 MHz, an insertion loss of 0.55 dB, and a second pass-band only at 2.8 GHz. The maximum input power handled by the filter amounted to 54 W, staying below the requirement. This power level was limited by electrical breakdown. Therefore, a high-power adaptation was devised and realised in an improved design subsequently. The resulting filter not only provided an even lower insertion loss of 0.37 dB but also handled more than 300 W input power.

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.

Efficient Design of Multilayer Microwave Modules using an Element-Wise Simulation Technique

A technique for the fast and efficient modeling of complex microwave modules is investigated. In order to reduce simulation and optimisation time of spatially extended transmission line structures, a library of basic microwave components together with an approach for the decomposition and cascaded simulation of extended microwave circuits is proposed. To verify the design method, simple test structures as well as constituents of challenging low temperature co-fired ceramics (LTCC) modules from an ongoing R& D project are analysed and evaluated. The promising results encourage further efforts to exploit the discussed method for automated design approaches.

Bandpass Filters for Ka-Band Satellite Communication Applications Based on LTCC

The design of two compact bandpass filters for Ka-band satellite communication applications (downlink 17-22 GHz) is presented. Both filters are designed with additional transmission zeros at finite frequencies in order to improve the out-of-band selectivity. The filters have been realised as low-cost LTCC modules and the scattering parameters have been measured with on-wafer probing.

Power transfer networks at RF frequencies: new design procedures with implementation roadmap

The purpose of this work is to provide the necessary background to design wide-band power transfer two-ports, or so-called broadband matching networks, at radio frequencies for wireless communication systems. The importance of the topic stems from the recent advances in the conceptual design and manufacturing technologies of the next-generation wireless and mobile communication systems, which will operate over ultra-wide frequency bands. In fact, for all communication systems, construction of wide-band power transfer networks is essential. Therefore, in this manuscript, new procedures to design broadband matching network are covered, and a design roadmap is given with relevant recommendations. As an example, the design of a compensation network for a RF switch matrix covering the band 17...23 GHz is presented, which employs the roadmap described in this work

Microwave crossovers using cascaded couplers for switching applications

The paper describes a passive solution for the implementation of transparent paths within a reconfigurable switch matrix for satellite communications, to improve its availability in case of power failure. The performance of four cascaded identical reduced-length couplers distributed across embedded layers of a ceramic multi-layer substrate has been presented, fulfilling return-loss, isolation and dimensional requirements. The simulated performance parameters will be verified by measurements in due course.