TOBY-R2 series - System integration manual
UBX-16010572 - R10
Design-in
Page 125 of 151
2.15.2
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 ANT1
and the ANT2 ports (antenna RF interfaces).
Ensure no coupling occurs between the RF interface and noisy or sensitive signals (primarily
analog audio input/output signals, SIM signals, high-speed digital lines such as SDIO, USB and
other data lines).
Optimize placement for minimum length of RF line.
Check the footprint and paste mask designed for TOBY-R2 series module as illustrated in section
VCC line should be wide and as short as possible.
Route VCC supply line away from RF lines / parts and other sensitive analog lines / parts.
The VCC bypass capacitors in the picoFarad range should be placed as close as possible to the
VCC pins, in particular if the application device integrates an internal antenna.
Ensure an optimal grounding connecting each GND pin with application board solid ground layer.
Use as many vias as possible to connect the ground planes on multilayer application board,
providing a dense line of vias at the edges of each ground area, in particular along RF and high
speed lines.
Keep routing short and minimize parasitic capacitance on the SIM lines to preserve signal
integrity.
USB_D+ / USB_D- traces should meet the characteristic impedance requirement (90
differential
and 30
common mode) and should not be routed close to any RF line / part.
Keep the SDIO traces short, avoid stubs, avoid coupling with any RF line / part and consider low
value series damping resistors to avoid reflections and other losses in signal integrity.
Ensure appropriate RF precautions for the Wi-Fi and Cellular technologies coexistence.
Ensure appropriate RF precautions for the GNSS and Cellular technologies coexistence as
described in the GNSS implementation application note
Route analog audio signals away from noisy sources (primarily RF interface, VCC, switching
supplies).
The audio outputs lines on the application board must be wide enough to minimize series
resistance.
2.15.3
Antenna checklist
Antenna termination should provide 50
characteristic impedance with V.S.W.R at least 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).
Ensure compliance with any regulatory agency RF radiation requirement, as reported in sections
for products marked with the FCC and/or IC.
Ensure high and similar efficiency for both the primary (ANT1) and the secondary (ANT2) antenna.
Ensure high isolation between the primary (ANT1) and the secondary (ANT2) antenna.
Ensure low Envelope Correlation Coefficient between the primary (ANT1) and the secondary
(ANT2) antenna: the 3D antenna radiation patterns should have radiation lobes in different
directions.
Ensure high isolation between the cellular antennas and any other antenna or transmitter.