60 GHz patch antennas in LTCC technology for high data-rate communication systems L. Alhouri, S. Rentsch, R. Stephan, J.F. Trabert, J. Müller, and M.A. Hein Institute for Micro- and Nanotechnologies, Technische Universität Ilmenau, PO Box 100565, 98684 Ilmenau, Germany Corresponding author: Luay Alhouri, Tel.: (0)3677 / 69-1580, Fax: -1586, E-mail: luay.alhouri@tu-ilmenau.de Topic areas: Antennas for Ultra-Wideband Systems // Technology for Antennas Short Abstract—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 dielec- tric-constant materials. For the experimental charac- terisation of the balanced layout with a coplanar wafer prober, a wide-band balun was designed, which trans- forms 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. Keywords - patch antenna; single-ended, balanced, 60 GHz, ceramic multilayer technology. I. INTRODUCTION The maximum data rate, which can be transferred by means of wireless local area networks (WLAN), is presently limited at around 54 Mbit/s [1]. To achieve much higher data rates, wired transmission systems still remain undispensable. Future wireless systems for high-speed data communications meet demands of data rates of the order of 1...10 Gbit/s over a range of about 10 m [2]. The broad bandwidth of approxi- mately 1...10 GHz required for such applications is available only at sufficiently high, namely millimetre wave, frequencies. In terms of the microwave elec- tronics suited for receivers and transmitters, present semiconductor technologies offer integrated circuits for frequencies up to about 70 GHz [3]. This contribution deals with design and technol- ogy issues for planar transmit and receive antennas for wireless transmission with high data rates. Patch antennas in microstrip technology combine numerous advantages like a planar geometry, small cross sec- tion, low weight and volume, appreciable antenna gain, a main lobe perpendicular to the surface of the circuit board, as well as straight-forward implementa- tion of antenna arrays [4,5]. We propose types of patch antennas which can be hybrid integrated with electronic circuitry, and which meet the requirements of realistic link budgets, e.g., an antenna gain of 10 dBi over a bandwidth from 59.5 to 60.5 GHz [6]. As a low-cost and reliable fabrica- tion technology, the ceramic multilayer technique based on low temperature co-fired ceramics (LTCC) has proven attractive even at these frequencies [6-8]. The antennas were simulated numerically, subse- quently fabricated, and measured in terms of reflec- tion and transmission. We have adapted the micro- wave design procedure such as to fully exploit the possibilities of the LTCC technology with the mini- mum required number of design iterations [9]. II. PATCH ANTENNA WITH SINGLE-ENDED FEED LINE As a first attempt towards a millimetre wave an- tenna based on LTCC technology, a conventional rectangular microstrip patch antenna was designed for a centre frequency of 60 GHz. The numerical simula- tion and optimisation was performed with the com- mercial software Ansoft HFSS 9.2 (finite element method) [10]. To keep the dielectric losses low, a material system optimised for high-frequency applica- tions was employed, DuPont ® DP943, with tanδ ≈ 0.002 specified for 40 GHz [11]. Dielectric losses deduced from measurements of the resonant frequen- cies and quality factors of ring resonators, performed in house, revealed ε r ≈ 7.4 and indicated an upper limit of tanδ ≈ 0.01 at 60 GHz [12]. As illustrated in Fig. 1, the patch antenna was fed by a microstrip transmission line. However, since the microwave test source required coplanar probe tips, a Fig. 1: Top view of the design of the microstrip-fed patch antenna with a coplanar test port and vias to the backside of the ground plane. The colours indicate the magnitude of the electrical field strength.