u-blox EVA-8M Series Hardware Integration Manual

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u-blox EVA-8M Series Hardware Integration Manual Manual pdf 27 page image

EVA-8M and EVA-M8 series - Hardware Integration ManualUBX-16010593 - R06 Design-in Page 27 of 47Early Production InformationLNA with appropriate ESDrating and maximum inputpower.Figure 7: EOS and ESD Precautions2.13.5 Electromagnetic interference (EMI)Electromagnetic interference (EMI) is the addition or coupling of energy, which causes a spontaneousreset of the GNSS receiver or results in unstable performance. In addition to EMI degradation due toself-jamming (see section 2.3.4), any electronic device near the GNSS receiver can emit noise that canlead to EMI disturbances or damage.The following elements are critical regarding EMI:• Unshielded connectors (e.g. pin rows etc.)• Weakly shielded lines on PCB (e.g. on top or bottom layer and especially at the border of a PCB)• Weak GND concept (e.g. small and/or long ground line connections)EMI protection measures are recommended when RF emitting devices are near the GNSS receiver. Tominimize the effect of EMI a robust grounding concept is essential. To achieve electromagneticrobustness follow the standard EMI suppression techniques.http://www.murata.com/products/emc/knowhow/index.htmlhttp://www.murata.com/products/emc/knowhow/pdf/4to5e.pdfImproved EMI protection can be achieved by inserting a resistor or better yet a ferrite bead or aninductor (see Table 16) into any unshielded PCB lines connected to the GNSS receiver. Place theresistor as close as possible to the GNSS receiver pin.Alternatively, feed-thru capacitors with good GND connection can be used to protect e.g. the VCCsupply pin against EMI. A selection of feed-thru capacitors are listed in Table 24.Intended use☞ In order to mitigate any performance degradation of a radio equipment under EMC disturbance,system integration shall adopt appropriate EMC design practice and not contain cables over threemeters on signal and supply ports.2.13.6 Applications with cellular modulesGSM terminals transmit power levels up to 2 W (+33 dBm) peak, 3G and LTE up to 250 mWcontinuous. Consult the corresponding product data sheet in Related documents for the absolutemaximum power input at the GNSS receiver. Make sure that absolute maximum input power level ofthe GNSS receiver is not exceeded.☞ See the GPS Implementation and Aiding Features in u-blox wireless modules [6].2.13.6.1 Isolation between GNSS and GSM antennaIn a handheld type design, an isolation of approximately 20 dB can be reached with careful placementof the antennas. If such isolation can’t be achieved, e.g. in the case of an integrated GSM/GNSSantenna, an additional input filter is needed on the GNSS side to block the high energy emitted by theGSM transmitter. Examples of these kinds of filters would be the SAW Filters from Epcos (B9444 orB7839) or Murata.2.13.6.2 Increasing interference immunityInterference signals come from in-band and out-band frequency sources.