u-blox NINA-B112 System Integration Manual

Also see for NINA-B111: Manual Getting started

u-blox NINA-B112 System Integration Manual Manual pdf 32 page image

NINA-B1 series - System Integration ManualUBX-15026175 - R09 Design-inPage 32 of 49Consider that SMT connectors are typically rated for a limited number of insertion cycles. In addition, the RFcoaxial cable may be relatively fragile compared to other types of cables. To increase application ruggedness,connect U.FL connector to a more robust connector such as SMA fixed on panel.A de-facto standard for SMA connectors implies the usage of reverse polarity connectors (RP-SMA) onWi-Fi and Bluetooth end products to increase the difficulty for the end user to replace the antenna withhigher gain versions and exceed regulatory limits.The following recommendations apply for proper layout of the connector:• Strictly follow the connector manufacturer’s recommended layout:o SMA Pin-Through-Hole connectors require GND keep-out (that is, clearance, a void area) on all thelayers around the central pin up to annular pads of the four GND posts.o UFL surface mounted connectors require no conductive traces (that is, clearance, a void area) in thearea below the connector between the GND land pads.• If the connector’s RF pad size is wider than the micro strip, remove the GND layer beneath the RFconnector to minimize the stray capacitance thus keeping the RF line 50 Ω. For example, the active padof the UF.L connector must have a GND keep-out (that is, clearance, a void area) at least on the firstinner layer to reduce parasitic capacitance to ground.3.2.2.2 Integrated antenna designIf integrated antennas are used, the transmission line is terminated by the integrated antennas themselves. Thefollowing guidelines should be followed:• The antenna design process should begin at the start of the whole product design process. Self-madePCBs and antenna assembly are useful in estimating overall efficiency and radiation path of the intendeddesign.• 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. Theground plane of the application PCB may be reduced down to a minimum size that must be similar toone quarter of wavelength of the minimum frequency that has to be radiated, however overall antennaefficiency may benefit from larger ground planes.Proper placement of the antenna and its surroundings is also critical for antenna performance. Avoidplacing the antenna close to conductive or RF-absorbing parts such as metal objects, ferrite sheets andso on as they may absorb part of the radiated power or shift the resonant frequency of the antenna oraffect the antenna radiation pattern.• It is highly recommended to strictly follow the detailed and specific guidelines provided by the antennamanufacturer regarding correct installation and deployment of the antenna system, including PCBlayout and matching circuitry.• Further to the custom PCB and product restrictions, antennas may require tuning/matching to complywith all the applicable required certification schemes. It is recommended to consult the antennamanufacturer for the design-in guidelines and plan the validation activities on the final prototypes liketuning/matching and performance measures (see Table 8).• RF section may be affected by noise sources like hi-speed digital buses. Avoid placing the antenna closeto buses such as DDR or consider taking specific countermeasures like metal shields or ferrite sheets toreduce 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 NINA-B1 modules.3.2.3 On-board antenna design (NINA-B112 only)Keep a minimum clearance of 5 mm between the antenna and the casing. Keep a minimum of 10 mm freespace from the metal around the antenna including the area below the antenna. If a metal enclosure is required,NINA-B111 with antenna pin has to be used.