Small, light weight and multifunctional electronic components are attracting much attention because of the rapid growth of the wireless communication systems and microwave products in the consumer electronic market. The component manufacturers are thus forced to search for new advanced integration, packaging and interconnection technologies. One solution is the low temperature cofired ceramic (LTCC) technology enabling fabrication of three-dimensional ceramic modules with low dielectric loss and embedded silver electrodes. During the past 15 years, a large number of new dielectric LTCCs for high frequency applications have been developed. About 1000 papers were published and ∼500 patents were filed in the area of LTCC and related technologies. However, the data of these several very useful materials are scattered. The main purpose of this review is to bring the data and science of these materials together, which will be of immense help to researchers and technologists all over the world. The comme...

Low loss dielectric materials for LTCC applications: a review

Microwave dielectric properties of A2+B6+O4 (A2+: Ca, Pb, Ba; B6+: Mo, W) ceramics were investigated as a function of packing fraction and bond valence. For A2+B6+O4 specimens sintered at 800–1100 °C for 3 h, a single phase with a tetragonal scheelite structure was detected, and the theoretical density was higher than 93% throughout the composition. Although the ionic polarizability of Ba2+ ion was larger than that of Ca2+ ion, the dielectric constant (K) of BaB6+O4 showed a smaller value than that of CaB6+O4. These results could be attributed to changes of the packing fraction due to the effective ionic size. The Q·f value was largely dependent on the packing fraction, as well as the percentages of theoretical density. The temperature coefficients of the resonant frequencies (TCFs) of the specimens were affected by the bond valence of oxygen. The specimens of CaMoO4 sintered at 1000 °C for 3 h showed the K of 10.8, Q·f of 76,990 GHz and TCF of −22.8 ppm/°C, respectively.

Effects of packing fraction and bond valence on microwave dielectric properties of A2+B6+O4 (A2+: Ca, Pb, Ba; B6+: Mo, W) ceramics

Wireless communication has led to an explosive growth of emerging consumer and military applications of radio frequency (RF), microwave and millimeter wave circuits and systems. Future personal (hand-held) and ground communications systems as well as communications satellites necessitate the use of highly integrated RF front-ends, featuring small size, low weight, high performance and low cost. Continuing chip scaling has contributed to the extent that off-chip, bulky passive RF components, such as high-Q inductors, ceramic and SAW filters, varactor diodes and discrete PIN diode switches, have become limiting. Micro-machining or MEMS technology is now rapidly emerging as an enabling technology to yield a new generation of high-performance RF-MEMS passives to replace these off-chip passives in wireless communication (sub)systems. This paper reviews the progress in RF-MEMS from a device and integration perspective. The worldwide state-of-the-art of RF-MEMS devices including switches, variable capacitors, resonators and filters are described. Next, it is stipulated how integration of RF-MEMS passives with other passives (as inductors, LC filters, SAW devices, couplers and power dividers) and, active circuitry (ASICs, RFICs) can lead to the so-called RF-MEMS system-in-a-package (RF-MEMS-SiP) modules. The evolution of the RF-MEMS-SiP technology is illustrated using IMEC's microwave multi-layer thin-film MCM-D technology which today already serves as a technology platform for RF-SiP.

https://iopscience.iop.org/article/10.1088/0960-1317/13/4/323/pdf

MEMS for wireless communications: 'from RF-MEMS components to RF-MEMS-SiP'

In this paper, internal low-volume antenna structures for mobile terminals are studied. The work concentrates on the possibilities to reduce the volume of mobile terminal antenna elements by efficiently utilizing the radiation of the currents on the mobile terminal chassis. Essentially nonresonant coupling elements are used to optimally couple to the dominating char- acteristic wavemodes of the chassis. The antenna structures are tuned to resonance with matching circuits. During the last few years, the approach has achieved growing interest—also among industrial manufacturers of mobile terminals. There exist, how- ever, no systematical feasibility and performance studies of the idea. During the work, two antenna models with very low-volume coupling elements are designed and in total four prototypes are constructed. The simulation and measurement results show that the studied antenna concept is a very promising alternative for traditional antenna technologies. The presented analysis provides useful and novel information for the designs of the future low-pro- file and low-volume mobile terminal antennas.

/pdf/coupling-element-based-mobile-terminal-antenna-structures-1qy0gie75a.pdf

Coupling element based mobile terminal antenna structures

Anew industrial revolution, often called the “third wave” or information technology (IT), is in the making. The products of this revolution will require entirely different systems hardware technologies: those with multifunctions, such as digital, analog, RF, and optical circuitries. RF and microwave design and packaging have been established as key technologies of this revolution. The demand for increasingly higher rates of data, voice, and video drives RF technology to ever higher frequencies where bandwidth for channel capacity is easy to find. Such emerging high-performance applications as personal communication networks, wireless local-area networks (WLAN), and RF-optical networks have defined a trend toward more flexible and reconfigurable systems. They impose very stringent specifications never before reached in term of low noise, high linearity, low power consumption, small size and weight, and low cost. The RF front-end module is the foundation of these systems, and its integration poses a great challenge. Microelectronics technology, since the invention of the transistor, has revolutionized many aspects of electronic products. This integration and cost path has led the microelectronics industry to believe that this kind of progress can go on forever, leading to so-called “system-on-chip” (SOC) for all applications. But it is becoming clear that the production of a complete solution for the new wireless communication front-end is still a dream. When you consider the characteristics of an RF front-end module  high performance up to 100-GHz operating frequency  a large number of high-performance discrete passive components  design flexibility

RF-system-on-package (SOP) for wireless communications

In this paper, we present the development and full characterization and modeling of a multilayer ceramic-based system-on-package component library. Compact high-Q three-dimensional inductor and capacitor topologies have been chosen and incorporated. A measured inductor Q factor as high as 100 and self-resonant frequency as high as 8 GHz have been demonstrated. The new vertically interdigitated capacitor topology occupies nearly an order of magnitude less of real estate while demonstrating comparable performance to the conventional topology. The low-temperature co-fired ceramic (LTCC) library has been incorporated into a 1.9-GHz CMOS power-amplifier design exhibiting a measured 17-dB gain, 26-dBm output power, and 48% power added efficiency. This power-amplifier module with fully integrated LTCC passives demonstrates a superior performance to those with full and partial on-chip passive integration.

Y.-J. Emery Chen

Papers

High-Q LTCC-based passive library for wireless system-on-package (SOP) module development