Novel Reconfigurable Multi-band Antennas for Multi-radio Platforms Songnan Yang 1 , Aly E. Fathy 1 , Samir M. El-Ghazaly 1 and Vijay K. Nair 2 1 EECS Department, University of Tennessee, Knoxville, TN 37996 2 Intel Corporation, Hillsboro, OR 97124 Abstract — Reconfigurable and multi-band concepts have been combined to design antennas for mobile multi-radio platforms. The new concept is based on reconfiguring a multi- branched low profile planar inverted-F antenna (PIFA) structure suitable for laptops applications. The developed unique structure complies with space and service requirements, and utilizes only two switches to provide two operating reconfigurable multi-band states. Each state is capable of covering specific service group to simplify service switching, and minimize out-of-band input noise. Index Terms — Mobile antennas, multi-frequency antennas, p-i-n diodes, reconfigurable architectures. I. INTRODUCTION Multi-band antennas are widely used for many multi- radio platforms, where either one service could have multiple standards utilized at different countries, or many services need to be simultaneously supported at the same country, but should be received through the same antenna. Reconfigurable antennas, on the other hand, are designed to switch to a desired service and to be solely dedicated to one service to achieve maximum out-of-band noise rejection performance. As the number of services increases, the development of either of these antennas becomes more and more challenging due to the fundamental limitations of the achievable bandwidth for a certain given volume for the former, while for the latter, its design becomes more complicated and suffer from high loss and unacceptable DC power consumption when using multiple switching devices. We propose here a novel hybrid reconfigurable multi- band antenna structures that is based on these two concepts. In other words, reconfiguring the multi-band antenna, where multitudes of switching devices are used to hop between several multi-band configurations. Through judicious grouping of frequency bands for each configuration, advantages of both the multi-band and the reconfigurable antenna structures can be simultaneously achieved while supporting more services. Our developed design for laptops is comprised of a compact reconfigurable multi-band twin PIFA structure, which supports essential wireless services for laptops (GSM850, PCS and WLAN) with only two configurations, one serving the cellular bands and the other covering WLAN frequencies. The designs have been optimized to minimize the number of switches, where only two are required. The multi-band construction strategy, switch integration schemes, and simulated and measured results of the novel design will be presented here in detail. II. RECONFIGURABLE MULTI-BAND ANTENNA DESIGN A. Frequency Band Grouping In order to support the required wireless services for laptop platforms listed in Table 1, the frequency bands need to be strategically grouped to minimize the number of switchable configurations while still covering the required services. The guidelines for this selective grouping include: 1). Different standards of the same services can be grouped together, since only one frequency band will only be used at a certain time in a specific country. For instance, the GSM850 and PCS bands can be grouped into one configuration. 2). Different services with close frequency bands need to be allocated at different configurations to improve out- of-band noise rejection. For example, 2.4GHz WLAN services need to be separated from the cellular service around 1.9GHz (PCS) to avoid its interference and simplify out-of-band noise filtering. According to our grouping criterions, the required services are separated into two distinct application groups as shown in Table 1. Cellular services including GSM850, PCS frequency bands are grouped together and classified as WWAN configuration. On the other hand, internet services including 802.11.a, b, g, and n are consolidated in the other configuration, which is utilized for WLAN services. For each configuration, a multi-band antenna is required. In most cases, two services from these grouped configurations will not be required to operate at the same time. TABLE I FREQUENCY GROUPING OF LAPTOP ANTENNA CONFIGURATIONS Unit: GHz WWAN Configuration WLAN Configuration Grouped Bands (8.3%) (7.3%) (3.5%) 4.9-5.35 (8.8%) Service GSM850 PCS 802.11 b/g/n 802.11 a Frequency 0.824-0.894 1.85-1.99 2.4-2.484 4.9-5.25 5.15-5.35 Country U.S. U.S. Universal Japan U.S. Indoor 1-4244-1463-6/08/$25.00  2008 IEEE RWS 2008 723