Modem User Manual

MTX-H15 UMTS-HSDPA terminal modem http://www.matrix.es
MTX-H15 User Manual V.2.0 Pag. 24
Preliminary. Subject to change without prior notice
7.2.2 Securing the modem
Before securing the modem take into account the amount of additional space required for the mating
connectors and cables that will be used in the application.
• Where access is restricted, it may be easier to connect all the cables to the modem prior to securing it in
the application.
• Securely attach the MTX-H15 Terminal modem to the host application using two 3mm diameter pan-
head screws
7.3 Antenna
7.3.1 General
The antenna is the component in your system that maintains the radio link between the network and the
modem. Since the antenna transmits and receives electromagnetic energy, its efficient function will
depend on:
• the type of antenna (for example, circular or directional);
• the placement of the antenna;
• communication disturbances in the vicinity in which the antenna operates.
In the sections below, issues concerning antenna type, antenna placement, antenna cable, and possible
communication disturbances are addressed. In any event, you should contact your local antenna
manufacturer for additional information concerning antenna type, cables, connectors, antenna placement,
and the surrounding area.
You should also determine whether the antenna needs to be grounded or not. Your local antenna
manufacturer might be able to design a special antenna suitable for your application.
7.3.2 Antenna type
Make sure that you choose the right type of antenna for the modem. Consider the following requirements:
• the antenna must be designed for the one of the frequency bands in use; please ask your network
provider for more information:
• UMTS 2100 MHz
• GSM 1800/1900 MHz;
• the impedance of the antenna and antenna cable must be 50Ω;
• the antenna output-power handling must be a minimum of 2W;
• the VSWR value should be less than 3:1 to avoid damage to the modem.
7.3.3 Antenna placement
The antenna should be placed away from electronic devices or other antennas. The recommended
minimum distance between adjacent antennas, operating in a similar radio frequency band, is at least
50cm. If signal strength is weak, it is useful to face a directional antenna at the closest radio base station.
This can increase the strength of the signal received by the modem. The modem’s peak output power can
reach 2W.
RF field strength varies with antenna type and distance. At 10cm from the antenna the field strength may
be up to 70V/m and at 1m it will have reduced to 7V/m. In general, CE-marked products for residential
and commercial areas, and light industry can withstand a minimum of 3V/m.
7.3.4 The antenna cable
Use 50Ω impedance low-loss cable and high-quality 50Ω impedance connectors (frequency range up to
2GHz) to avoid RF losses. Ensure that the antenna cable is as short as possible. The Voltage Standing-
Wave Ratio (VSWR) may depend on the effectiveness of the antenna, cable and connectors. In addition, if
you use an adapter between the antenna cable and the antenna connector, it is crucial that the antenna
cable is a high-quality, low-loss cable. Minimize the use of extension cables, connectors and adapters.
Each additional cable, connector or adapter causes a loss of signal power.