Huawei EM820W manual Antenna Design Requirements, Antenna Design Indicators

HUAWEI EM820W HSPA+ PC Embedded Module
Hardware Guide	RF Specifications

4.4 Antenna Design Requirements

4.4.1 Antenna Design Indicators

Antenna Efficiency

Antenna efficiency is the ratio of the input power to the radiated or received power of an antenna. The radiated power of an antenna is always lower than the input power due to the following losses: return loss, material loss, and coupling loss. The efficiency of an antenna relates to its electrical dimensions. To be specific, the antenna efficiency increases with the electrical dimensions. In addition, the transmission cable from the antenna port of the EM820W to the antenna is also part of the antenna. The cable loss increases with the cable length and the frequency. It is recommended that the cable loss should be as low as possible, for example, U.FL- LP-088 made by HRS.

The following antenna efficiency (free space) is recommended for the EM820W on a laptop to ensure high radio performance of the EM820W:

zEfficiency of the master antenna > 40% (-4 dB)

zEfficiency of the slave antenna > 40% (-4 dB)

zEfficiency of the GPS antenna > 50% (-3 dB)

zEfficiency of the Wi-Fi antenna > 40% (-4 dB)

Isolation

For a wireless device with multiple antennas, the power of different antennas is coupled with each other. Antenna isolation is used to measure the power coupling. The power radiated by an antenna might be received by an adjacent antenna, which decreases the antenna radiation efficiency and affects the running of other devices. To avoid this problem, evaluate the antenna isolation as sufficiently as possible at the early stage of antenna design.

Antenna isolation depends on the following factors:

zDistance between antennas

zAntenna type

zAntenna direction

The master antenna must be placed as near as possible to the EM820W to minimize the cable length. The slave antenna needs to be installed perpendicularly to the master antenna. The slave antenna can be placed farther away from the EM820W. Antenna isolation can be measured with a two-port vector network analyzer.

The following antenna isolation is recommended for the antennas on laptops:

zIsolation between master and slave antennas < -12 dB

zIsolation between the master antenna and the GPS antenna < -15 dB

zIsolation between the slave antenna and the Wi-Fi antenna < -15 dB

If a Wi-Fi module is installed on the laptop, the following measures must be taken to reduce mutual influence between the data card module and the Wi-Fi module:

Issue 01 (2010-12-31)	Huawei Proprietary and Confidential	20
	Copyright © Huawei Technologies Co., Ltd.