AMC_WiFi_BT - Revision B 2/14/03 6100-C Frost Place Laurel,...

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1 Antenna 1 Antenna 2 Vertical Electric Field Lines Laptop Screen Metal Housing (No Surface Treatment) Figure 2. Antennas set up surface waves and currents that propagate along the metal housing of a laptop. Abstract: An artificial magnetic conductor (AMC) is employed as an edge treatment for reducing the mutual coupling between antennas on laptop computers. Specifically, a Bluetooth antenna and an 802.11b antenna are isolated by a minimum of 45 dB in the 2.4 GHz ISM band. I. Introduction The Bluetooth TM wireless standard was developed for short-range communication applications such as wireless print sharing, cordless mouse or keyboard operation, and ad hoc networking. This standard uses a frequency-hop spread spectrum modulation technique within the 2.4 GHz ISM band (2.4 - 2.48 GHz). The IEEE 802.11b wireless networking protocol utilizes this same frequency band with direct sequence spread spectrum modulation. 802.11b has much greater range than Bluetooth and is used to provide wireless Internet access and file sharing within homes and offices as well as over campuses. Bluetooth 802.11b Figure 1. A laptop enabled with Bluetooth and 802.11b radios. Although spread spectrum signals are designed to look like noise to non-intended receivers, there still significant interference problems when 802.11b and Bluetooth radios are located on the same platform. The use of two antennas with low reduces i nterference between 802.11b and Bluetooth systems. Usually, antennas located on a laptop computer have 15 to 25 dB of isolation. In the case of Bluetooth and 802.11b systems, 30 to 40 dB is typically required for these systems to coexist [1]. II. Coupling of Antennas on a Laptop Shown in Figure 2 are antennas located on the top and side of a laptop computer screen. Typically, a metal frame surrounds the edges of the LCD display. This metal frame presents a surface to which electric fields attach. The antennas couple energy through surface waves and currents that Artificial Magnetic Conductor (AMC) Technology Enables the Coexistence of 802.11b and Bluetooth TM 6100-C Frost Place Laurel, MD 20707 (240) 456-4100 Fax: (240) 456-0655 Shawn Rogers, Will McKinzie, Greg Mendolia Revision B 2/14/03
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2 (a) (b) Figure 3. Conventional surface treatments, (a) MAGRAM, (b) R-card. Artificial Magnetic Conductor H tan ~ 0 E tan AMC Perfect Magnetic H tan = 0 E PMC (a) (b) E tan = 0 Perfect Electric H PEC (c) Figure 4. The AMC is an engineered material with the same boundary condition as a PMC. The PMC is the opposite of a PEC. propagate along the metal. Significant mutual coupling of antennas means that the antennas are not well isolated. Before getting to techniques on how to improve isolation, lets briefly review the concept of isolation.
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AMC_WiFi_BT - Revision B 2/14/03 6100-C Frost Place Laurel,...

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