User's Manual

HiLo3G-850 User Manual
04 March 2011 - Page 31 / 36
 Do not add signal unvarnished layout trace on the first layer of the customer board, or unvarnished via holes under the
module shield area or it will result on short circuit on those signals. This is mandatory.
Free CAD software can be used to compute the stack-up parameters that leads to a compliant 50Ω RF track.
6.4 Mechanical Surrounding
Do not apply mechanical pressure over the HiLo3G-850 shield, doing so could damage the mechanical structure of the
shield and lead to internal short-circuits or other undesirable issues.
Avoid letting any metallic part be around the antenna area
Keep FPCs and battery contact (if any) away from antenna area.
 FPC's (if any) have to be shielded
6.5 Other Recommendation—test for production/design
SagemCom guarantees the RF performances in conductive mode but strongly recommends making RF measurements in an
anechoic chamber in radiated mode (tests conditions for FTA): the radiated performances strongly depend on radio
integration (layout, antenna, matching circuit, ground area…..)
7. Audio Integration
Audio mandatory tests for FTA are done in handset mode only so a particular care must be taken to the design of audio
(mechanical integration, gasket, electronic) in this mode.
The audio norms which describe the audio tests are 3GPP TS 26.131 & 3GPP TS 26.132.
7.1 Mechanical integration and acoustics
Particular care to Handset Mode:
To get a better audio output design (speaker part) :
The speaker must be completely sealed on the front side.
The front aperture must be compliant with speaker supplier‘s specifications
The back volume must be completely sealed.
The sealed back volume must be compliant with speaker supplier‘s specifications
Take care of the design of the speaker gasket (elastomer).
 Foresee a stable and large enough area for the gasket of the artificial ear.
To get a better audio input design (microphone part) :
Take care of the design of the microphone (elastomer).
All receivers must be completely sealed on the front side.
 Microphone sensitivity depends on the shape of the device eg. about –40 ±3 dBV/Pa.
Promote the use of pre-amplified microphone. If needed, use a pre-amplification stage.
As audio input and output are strongly linked:
Place the microphone and the speaker as far as possible from one another.
7.2 Electronics and layout
Avoid Distortion & Burst noise
 Audio signals must be symmetric (same components on each path).
Differential signals must be routed parallel.
Audio layer must be surrounded by 2 ground layers.
The link from one component to the ground must be as short as possible.
If possible separate the PCB of the microphone and the one of the speaker.
Reduce as many as possible the number of electronics components (loss of quality, more dispersion).