u-blox LEXI-R422, Руководство по системной интеграции

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LEXI-R422 - System integration manual
UBX-23007449 - R02 Design-in Page 63 of 108
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2.4.3.2 Guidelines for ANT_DET layout design
Figure 41 describes the recommended layout for the antenna detection circuit to be provided on the
application board to achieve antenna detection functionality, implementing the recommended
schematic described in the previous
Figure 40 and Table 25 :
• The ANT pin must be connected to the antenna connector by means of a 50  transmission line,
implementing the design guidelines in section 2.4.1.4 and the recommendations of the SMA
connector manufacturer.
• DC blocking capacitor at ANT pin (C2) must be placed in series to the 50  RF line.
• The ANT_DET pin must be connected to the 50  transmission line by means of a sense line.
• Choke inductor in series at the ANT_DET pin (L1) must be placed so that one pad is on the 50 
transmission line and the other pad represents the start of the sense line to the ANT_DET pin.
• The additional components (R1, C1 and D1) are provided as ANT_DET ESD protection.
•
The additional high pass filter (C3 and L2) is provided as ESD immunity improvement.
LEXI module
C2
R1 D1
C1
L1
J1
C3
L2
Figure 41: Suggested layout for antenna detection circuit on application board
☞
See section 2.4.1.6 for the description of the antenna trace design implemented on the u-blox host
printed circuit board used for conformity assessment of LEXI-R422 surface-mounted modules for
regulatory type approvals such as FCC United States, ISED Canada, RED Europe, etc.
2.4.4 Cellular antenna dynamic tuner interface
LEXI-R422 modules include two output pins (named RFCTRL1 and RFCTRL2 ) that can be configured,
as optional feature, to change their output value dynamically according to the specific actual cellular
band in use by the module. These pins, paired with an external antenna tuner IC or RF switch, can be
used to:
•
Tune antenna impedance to reduce power losses due to mismatch
• Tune antenna aperture to improve total antenna efficiency
• Select the optimal antenna for each operating band
Figure 42 shows the example application circuits implementing impedance tuning and aperture
tuning. The module controls an RF switch which is responsible for selecting the appropriate matching
element for the operating band.
Table 26 reports suggested components implementing the SP4T RF
switch functionality.