LISA-U series - System Integration Manual
UBX-13001118 - R17
Advance information
Design-In
Page 127 of 190
2.1.2
Layout checklist
The following are the most important points for a simple layout check:
Check 50
nominal characteristic impedance of the RF transmission line connected to the
ANT
pad
(main RF input/output) and to the
ANT_DIV
pad (RF input for Rx diversity).
Follow the recommendations of the antenna producer for correct antenna installation and deployment
(PCB layout and matching circuitry).
Ensure no coupling occurs with other noisy or sensitive signals (primarily analog audio input/output
signals, SIM signals).
VCC
line should be as wide and as short as possible.
Provide the suggested series ferrite bead and bypass capacitors close to the
VCC
pins implementing the
recommended layout and placement, especially if the application device integrates an internal antenna.
Route
VCC
supply line away from sensitive analog signals.
The high-power audio outputs lines on the application board must be wide enough to minimize series
resistance.
Ensure proper grounding.
Consider “No-routing” areas for the Data Module footprint.
Optimize placement for minimum length of RF line and closer path from DC source for
VCC
.
Design
USB_D+ / USB_D-
connection as 90
differential pair, with 30
common mode impedance.
Keep routing short and minimize parasitic capacitance on the SPI lines to preserve signal integrity.
Keep routing short and minimize parasitic capacitance on
CODEC_CLK
line to preserve signal integrity.
2.1.3
Antenna checklist
Antenna should have 50
impedance, V.S.W.R less than 3:1 (recommended 2:1) on operating bands in
deployment geographical area.
Follow the recommendations of the antenna producer for correct antenna installation and deployment
(PCB layout and matching circuitry).
Follow the additional guidelines for products marked with the FCC logo (United States only) reported in
section 1.15.2.2
The antenna connected to the
ANT
pad should have built in DC resistor to ground to get proper
antenna detection functionality.
The antenna for the Rx diversity connected to the
ANT_DIV
pin should be carefully separated from the
main Tx/Rx antenna connected to the
ANT
pin: 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, for proper spatial diversity
implementation.
