User's Manual

page 45/51
HiAll
NC
User Manual 2012/06/28
9. AUDIO INTEGRATION
FTA audio mandatory tests only deal with handset mode so a particular care must be brought to the design of
audio (mechanical integration, gasket, electronic) in this mode.
The audio related standard are 3GPP TS 26.131 & 3GPP TS 26.132.
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Note that acoustic competences are mandatory to get accurate audio performance on customer’s product.
9.1 MECHANICAL INTEGRATION AND ACOUSTICS
Particular care to Handset Mode:
To achieve a more ideal audio output design (speaker part):
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The speaker must be completely sealed on front side.
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The front aperture must be compliant with the speaker supplier’s specifications
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The back volume must be completely sealed.
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The sealed back volume must be compliant with the speaker supplier’s specifications
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Pay attention to the design of the speaker gasket (elastomer).
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Make sure to leave sufficient space for the artificial ear gasket.
To achieve a more ideal audio input design (microphone part):
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Pay attention to the design of the microphone (elastomer).
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All receivers must be completely sealed on front side.
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Microphone sensitivity depends on the shape of the device but should be in the range of –40 ±3 dBV/Pa.
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Recommend to use the pre-amplified microphone. If needed, use a pre-amplification stage.
As audio input and output are strongly linked:
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Place the microphone and the speaker as far away as possible from one another.
9.2 ELECTRONICS AND LAYOUT
Avoid Distortion & Burst noise
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Audio signals must be symmetric (same components on each path).
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Differential signals must be routed in parallel.
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Audio layer must be surrounded by 2 ground layers.
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The link from one component to the ground must be as short as possible.