JODY-W2 - System integration manual
UBX-18068879 - R14
Design-in
Page 26 of 84
C1 - Public
•
The antenna design process should start together with the mechanical design of the product. PCB
mock-ups are useful in estimating overall efficiency and radiation path of the intended design
during early development stages.
•
Use antennas designed by an antenna manufacturer providing the best possible return loss (or
VSWR).
•
Provide a ground plane large enough according to the related integrated antenna requirements.
The ground plane of the application PCB may be reduced down to a minimum size that must be
similar to one quarter of wavelength of the minimum frequency that has to be radiated, however
overall antenna efficiency may benefit from larger ground planes. Proper placement of the
antenna and its surroundings is also critical for antenna performance. Avoid placing the antenna
close to conductive or RF-absorbing parts such as metal objects or ferrite sheets as they may
absorb part of the radiated power, shift the resonant frequency of the antenna or affect the
antenna radiation pattern.
•
It is highly recommended to strictly follow the specific guidelines provided by the antenna
manufacturer regarding correct installation and deployment of the antenna system, including
PCB layout and matching circuitry.
•
Further to the custom PCB and product restrictions, antennas may require tuning/matching to
reach the target performance. It is recommended to plan measurement and validation activities
with the antenna manufacturer before releasing the end-product to manufacturing.
•
The receiver section may be affected by noise sources like hi-speed digital busses. Avoid placing
the antenna close to busses as DDR or consider taking specific countermeasures like metal
shields or ferrite sheets to reduce the interference.
Take care of interaction between co-located RF systems like LTE sidebands on 2.4 GHz band.
Transmitted power may interact or disturb the performance of JODY-W2 modules where specific LTE
filter is not present.
2.3
Supply interfaces
Module supply design
Though the GND pins are internally connected, it is recommended to connect all the available ground
pins to solid ground on the application board as a good (low impedance) connection to external ground
can minimize power loss and improve RF and thermal performance. JODY-W2 modules must be
sourced through
VBAT
and
VIO
/
1V8
pins with proper DC power supplies that comply with the
requirements summarized in
Good connection of the JODY-W2 series module power supply pins with DC supply source is required
for accurate RF performance. Schematic guidelines for the supply design are summarized below:
•
All power supply pins must be connected to an appropriate DC source.
•
Any series component with Equivalent Series Resistance (ESR) greater than a few m
Ω
should be
avoided. Only exceptions to this rule are ferrite beads used for DC filtering, however those parts
should be used carefully to avoid instability of the DC/DC supply powering the module and are in
general not required.
•
A minimum bulk capacitance of 10 µF on
VBAT
rail is required close to the module to help filter
current spikes from the RF section. The preferred choice is a ceramic capacitor with X7R or X5R
dielectric due to low ESR/ESL. Special care should be taken in the selection of X5R/X7R dielectrics
due to capacitance derating vs DC bias voltage.
•
Additional bypass capacitors in the range of 100nF to 1µF on all supply pins are required for high
frequency filtering. The preferred choice is a ceramic capacitor with X7R or X5R dielectric due to
low ESR/ESL. The temperature characteristics shall also be considered where X7R is
recommended up to 125 °C, X6R up to 105 °C, and X5R up to 85 °C. Smaller size bypass capacitors
should be chosen for the manufacturing process to minimize ESL.
