User's Manual

TOBY-R2 series - System Integration Manual
UBX-16010572 - R04 Design-in
Page 124 of 147
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 2.11.
 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 [13].
 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 4.2.2
and/or 4.3.1 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.