LISA-U2 series - System integration manual
UBX-13001118 - R27
Design-In
Page 133 of 183
C1-Public
GSM antennas are typically available as:
•
Linear monopole: typical for fixed applications. The antenna extends mostly as a linear element
with a dimension comparable to lambda/4 of the lowest frequency of the operating band. Magnetic
base may be available. Cable or direct RF connectors are common options. The integration
normally requires the fulfillment of some minimum guidelines suggested by antenna
manufacturer
•
Patch-like antenna: better suited for integration in compact designs (e.g. mobile phone). These
are mostly custom designs where the exact definition of the PCB and product mechanical design
is fundamental for tuning of antenna characteristics
For integration observe these recommendations:
•
Ensure 50
Ω
antenna termination, minimize the VSWR or return loss, as this will optimize the
electrical performance of the module. See sections
•
Select the antenna with the best radiating performance. See section
•
If a cable is used to connect the antenna radiating element to application board, select a short
cable with minimum insertion loss. The higher the additional insertion loss due to low quality or
long cable, the lower the connectivity
•
Follow the recommendations of the antenna manufacturer for correct installation and
deployment
•
Do not include antenna within closed metal case
•
Do not place the main antenna in close vicinity to the end user since the emitted radiation in
human tissue is limited by S.A.R. regulatory requirements
•
Do not use directivity antenna since the electromagnetic field radiation intensity is limited in some
countries
•
Take care of interactions between co-located RF systems since the GSM transmitted power may
interact or disturb the performance of companion systems
•
Place the antenna far from sensitive analog systems or employ countermeasures to reduce
electromagnetic compatibility issues that may arise
•
The antenna for the Rx diversity should be carefully separated from the main Tx/Rx antenna,
because signal improvement is dependent on the cross correlation and the signal strength levels
between the two received signals. The distance between the two antennas should be at least
greater than half a wavelength of the lowest used frequency (i.e. distance greater than ~20 cm,
for 2G/3G low bands) to distinguish between different multipath channels