Multi-band RF and mm-Wave Design Solutions for Integrated RF Functions in Liquid Crystal Polymer System-On-Package Technology V. Palazzari 1 , D. Thompson 2 , N. Papageorgiou 2 , S. Pinel 2 , J. H. Lee 2 , S. Sarkar 2 , R. Pratap 2 , G. DeJean 2 , R. Bairavasubramanian 2 , R.-L. Li 2 , M. Tentzeris 2 , J. Laskar 2 , J. Papapolymerou 2 , L. Roselli 1 1 Dipartimento di Ingegneria Elettronica e dell’Informazione, Universita' di Perugia, via Duranti 93, I-06125, Perugia, Italy. Fax: (+39)0755853654, Email: palazzari@diei.unipg.it 2 Georgia Electronic Design Center, School of Electrical and Computer Engineering Georgia Institute of Technology, Atlanta GA 30332-0269 USA Fax:(404) 894-0222, Email: pinel @ece.gatech.edu Abstract Electronic packaging evolution involves systems, technology and material considerations. In this paper, we present a liquid crystal polymer (LCP) based multilayer packaging technology that is rapidly emerging as an ideal platform for low cost, multi-band and reconfigurable RF front-end module integration. LCP’s very low water absorption (0.04%), low cost and high electrical performance makes it very appealing for RF applications. Here we describe main characteristics and real performance of LCP substrate, by means of several design examples. A Single-Input-Single- Output (SISO) dual-band filter operating at ISM 2.4-2.5 GHz and UNII 5.15-5.85 GHz frequency bands, a dual polarization, dual frequency 2x1 antenna operating at 14 and 35 GHz, and a WLAN IEEE 802.11a compliant compact module (volume of 75x35x0.2 mm 3 ) have been fabricated on LCP substrate, showing the great potential of the System-On- Package approach for 3D compact, multi-band and reconfigurable integrated RF and millimeter waves functions and modules. Introduction Miniaturization, portability, cost and performance have been the driving force for the evolution of packaging and system-on-package (SOP) approach in RF, microwave and millimeter wave applications. Recent research shows SOP to be a more feasible and low cost solution than system-on-chip (SOC) approach [1]. Cost, electrical performance, integration density, and packaging compatibility are variables that are often at odds with each other in RF designs. Few material technologies are able address these considerations simultaneously. LTCC is a technology that has excellent electrical performance, dense multilayer integration, and good barrier properties, but it is relatively expensive compared to standard FR4. Most other substrate and packaging materials do not have low enough water absorption properties in tandem with multilayer construction capabilities to be considered for vertically integrated designs. Liquid crystal polymer (LCP) provides the all-in-one solution for such integration approach in terms of high quality dielectric for high performance multiband passive design, excellent substrate for heterogeneous SOP integration as well as for MEMS structures, enabling the implementation of multiband and reconfigurable modules. In this paper, we present the potential of LCP as the substrate as well as the packaging material for wireless applications. In the following sections, the LCP fabrication process, its main characteristics and design examples will be described. A Single-Input-Single-Output (SISO) WLAN dual-band filter using the novel “dual behaviour resonators” technique will be shown. Exploiting the strong second resonant frequency of resonators to realize the filtering response, allows for achieving the asymmetric shape and the good rejection between the two bands. A good agreement between simulation and measurements results will be reported. A dual polarization, dual frequency 2x1 antenna array on LCP will also be presented. The frequencies of operation are 14 and 35 GHz. The 14 GHz antenna array is placed on the top layer of the LCP substrate, while the 35 GHz antennas are “sandwiched” in between the 14 GHz array and the ground plane on an embedded layer. Both arrays are fed by microstrip lines printed on the same layer as the corresponding array. The control of polarizations can be realized by the use of two small gaps in the feed lines, which introduces a small capacitance in each gap. Each array has been simulated and measured, separately, showing good agrrement. This design exhibits a high efficiency and a low cross-polarization level. Finally an example of WLAN IEEE 802.11a compliant module on LCP will be also shown to demonstrate the power of this technology. A wireless transceiver system has been implemented, exploiting the capability of LCP to enable for low loss interconnections as well as for integration of embedded passives. It includes up-converting and down- converting stages, image canceling BPFs, PA module and variable gain LNA on the receiver side. The system has been measured and experimental results will be reported to show the great potential of the LCP as a valid altrnative for MCM and SOP approaches. LCP Process and Integration Concept Multi-layer substrates have been and still are of great interest for research in the area of the 3D integration of RF and millimeter waves functions and module using the System- on-Package (SOP) approach. Our research has been focused mainly on advanced multi- layer organic substrates using FR4 material and advanced material such as liquid crystal polymer (LCP), as well as on ceramic based platform such as Low Temperature Co-fired Ceramic (LTCC). The choice of the most suitable technology depends on the application specifications such as environment, frequency of operation, performances, volume and cost. Multi Layer Organic substrates are now widely developed and used in the High Density Interconnect (HDI) 0-7803-8365-6/04/$20.00 ©2004 IEEE 2004 Electronic Components and Technology Conference 1658