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XT65/XT75 Hardware Interface Overview
4 GSM Antenna Interface
4
GSM Antenna Interface
The GSM interface has an impedance of 50Ω. XT65/XT75 is capable of sustaining a total mismatch at the
antenna connector without any damage, even when transmitting at maximum RF power. DC electric strength is
given (see
Table
11).
The external antenna must be matched properly to achieve best performance regarding radiated power, DC-
power consumption, modulation accuracy and harmonic suppression. Antenna matching networks are not
included on the XT65/XT75 PCB and should be placed in the host application.
Regarding the return loss XT65/XT75 provides the following values in the active band:
Table 6: Return loss in the active band
State of module
Return loss of module
Receive
> 8dB
Transmit
not applicable
4.1
Antenna Installation
To suit the physical design of individual applications XT65/XT75 offers two alternative approaches to connecting
the antenna:
•
Recommended approach: U.FL-R-SMT antenna connector from Hirose assembled on the component side of
the PCB.
See
Section 4.3
for connector details.
•
Antenna pad and grounding plane placed on the bottom side. See
The U.FL-R-SMT connector has been chosen as antenna reference point (ARP) for the Siemens reference
equipment submitted to type approve XT65/XT75. All RF data specified throughout this manual are related to the
ARP. For compliance with the test results of the Siemens type approval you are advised to give priority to the
connector, rather than using the antenna pad.
IMPORTANT: Both solutions can only be applied alternatively. This means, whenever an antenna is plugged to
the Hirose connector, the pad must not be used. Vice versa, if the antenna is connected to the pad, then the
Hirose connector must be left empty.
XT65_XT75_HO_v00.130
Confidential / Preliminary
Recommended return loss of application
> 12dB
> 12dB
Figure 1: GSM antenna connector placement
Page 20 of 67
s
Section
4.2.
2006-10-12
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