Installation Instructions

LISA-U2 series - System Integration Manual
UBX-13001118 - R19 Early Production Information Design-In
Page 114 of 175
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 (e.g. 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.