Novel Substrate-independent Broadband Micromachined Antennas for mm- wave Cognitive Radio Applications Terence Wu*, Anya Traille, Li Yang, Bo Pan, John Papapolymerou and Manos M. Tentzeris Georgia Electronic Design Center, School of ECE, Georgia Institute of Technology, Atlanta, GA 30332-0250, U.S.A. E-mail: gtg562b@mail.gatech.edu Abstract: In this paper, novel U-slot and Yagi-Uda micromachined patch antennas were designed based on the “micromachined elevation” technique to improve the performance of mm-wave cognitive radios in terms of gain, weight and bandwidth. The elevated antennas were fed with a micromachined probe connected to a CPW line on top of a high ε r substrate. By elevating the antenna from the high ε r substrate, high-performance antenna designs can coexist with compact feed networks in 3D module configurations. A 10dB impedance bandwidth of 31% and 25% were obtained for the U-slot and Yagi designs, respectively. I. Introduction With the continuous quest for high data rate, low power, low cost, lightweight and compact communication systems with cognitive capabilities, the easy integration of components into a single package becomes increasingly important [1]. To achieve higher compactness and higher thermal dissipation, the signals are often carried through high-index substrates. However, the antenna performance is greatly compromised on these substrates due to high surface waves. Micromachining techniques compatible with the MMIC process have been already demonstrated in [2]-[4], exhibiting a significant improvement in the antenna performance on top of high-index substrates that is suitable for SOP design. Specifically in [3], an impedance bandwidth of 9.4% was achieved in a single elevated patch antenna with epoxy posts. In this paper, the bandwidth of micromachined elevated patch antenna in [3] and [4] is further improved by designing mechanically stable U-slot and Yagi-Uda antennas on these elevated topologies. The two antennas demonstrated high bandwidth around 25 and 70 GHz suitable for truly cognitive Local Multipoint Distribution Service (LMDS) and Wireless Personal Area Network (WPAN) applications. II. Antenna Design and Performance The U-slot patch antenna uses an additional slot to introduce another resonance to a regular patch antenna[5]. The antenna is fed with a metal coated micromachined 5833 1-4244-0878-4/07/$20.00 ©2007 IEEE