Sierra Wireless WISMO218 Manuale Utente

WA_DEV_W218_PTS_002

Rev 005

Page 81 of 109

Product Technical Specification &

Customer Design Guidelines

Table 39. Antenna Specifications

Characteristic

WISMO218

E-GSM 900

DCS 1800

TX Frequency

880 to 915 MHz

1710 to 1785 MHz

RX Frequency

925 to 960 MHz

1805 to 1880 MHz

Impedance



VSWR

Rx max

1.5 :1

Tx max

1.5 :1

Typical radiated gain

0dBi in one direction at least

Caution: Sierra Wireless strongly recommends working with an antenna manufacturer either to develop an

antenna adapted to the application or to adapt an existing solution to the application. Both the
mechanical and electrical antenna adaptations are one of the key issues in the design of the GSM
terminal.

The RF antenna connection uses one of the castellation pins of the WISMO218, with grounded
castellation pins at both sides.

This castellation pin must be connected to an RF 50 line, in order to protect the antenna line from
the noise coming from base-band signals.

Figure 41. Example of an RF 50

 line

This 50 line is surrounded by two ground planes in order to protect this antenna line from noise.
The length of the line shouldn’t be too long (more than a few centimeters) because of RF insertion
loss. The width of the line must be calculated in order to ensure a 50 characteristic impedance.

For this same reason, the RF embedded line should likewise be kept about 1cm away from any (noisy)
baseband signal in order to ensure a good RX sensitivity level.

The other end of the RF 50 line can be connected to an RF connector or a soldering pad in order to
connect an antenna.

Castellation pin for ANT

 RF line