ANNA-B112 - System integration manual
UBX-18009821 - R09
Design-in
Page 44 of 66
C1-Public
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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,
ferrite sheets and so on as they may absorb part of the radiated power or shift the resonant
frequency of the antenna or affect the antenna radiation pattern.
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It is highly recommended to strictly follow the detailed and specific guidelines provided by the
antenna manufacturer regarding correct installation and deployment of the antenna system,
including PCB layout and matching circuitry.
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Further to the custom PCB and product restrictions, antennas may require tuning/matching to
comply with all the applicable required certification schemes. It is recommended to consult the
antenna manufacturer for the design-in guidelines and plan the validation activities on the final
prototypes like tuning/matching and performance measures (see Table 13).
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RF section may be affected by noise sources like hi-speed digital buses. Avoid placing the antenna
close to buses such as DDR or consider taking specific countermeasures like metal shields or
ferrite sheets to reduce the interference.
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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 ANNA-B112 module.
Supply interfaces
3.3.1
Module supply design
Good connection of the module’s VCC pin with DC supply source is required for correct RF
performance. The guidelines are summarized below:
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The VCC connection must be as wide and short as possible.
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The VCC connection must be routed through a PCB area separated from sensitive analog signals
and sensitive functional units. It is a good practice to interpose at least one layer of PCB ground
between VCC track and other signal routing.
There is no strict requirement of adding bypass capacitance to the supply net close to the module.
But depending on the layout of the supply net and other consumers on the same net, bypass
capacitors might still be beneficial. Though the GND pins are internally connected, connect all the
available pins to solid ground on the application board, as a good (low impedance) connection to an
external ground can minimize power loss and improve RF and thermal performance.
Data communication interfaces
3.4.1
Asynchronous serial interface (UART) design
The layout of the UART bus should be done so that noise injection and cross talk are avoided.
It is recommended to use the hardware flow control with RTS/CTS to prevent temporary UART buffer
overrun.
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If CTS is 1, then the Host/Host Controller is allowed to send.
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If CTS is 0, then the Host/Host Controller is not allowed to send.
