CM-42 Technical Description
PAGE 37 OF 38
SEM/CX-02:0076/DES A
2.6.4 Antenna
2.6.4.1 Antenna Type
When choosing an antenna for your application you must consider the following requirements:
•
The antenna must be designed for the AMPS/CDMA 800 and CDMA 1900 MHz frequency band (dual band)
for the CM-42.
•
The impedance of the antenna and antenna cable must be 50
Ω
.
•
The VSWR value should be less than 2:1.
2.6.4.2 Antenna Placement
Always follow the instructions supplied by the antenna manufacturer.
You should place the antenna away from electronic devices or other antennas. The recommended minimum
distance between adjacent antennas operating in a similar radio frequency band is at least 50 centimetres.
If the module is used in the Class I AMPS mode, a separation distance of at least 20 centimeters must be
maintained between the radiating antenna and the user or nearby persons. In this mode of operation, the combined
connection cable path loss and antenna gain must also be no greater than 1 dBi.
2.6.4.3 Possible Communication Disturbances
•
Noise
can be caused by electronic devices and radio transmitters.
•
Free Space
Path-loss
occurs as the strength of the received signal steadily decreases with the distance from
the transmitter.
•
Shadowing
is a form of environmental attenuation of radio signals that is caused by hills, buildings, trees or
even vehicles. Inside buildings this can cause problems, especially if the walls are thick and reinforced.
•
Multi-path fading
is a sudden decrease or increase in the signal strength. This is the result of interference
caused when direct and reflected signals reach the mobile phone simultaneously. Flat surfaces such as
buildings, streets, vehicles, etc, can reflect signals.
