u-blox ANTARIS 4 User Manual

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driving large bus systems.Alternatively, high-speed signallinescan be terminated with resistors or evenactive
terminationstoreducehighfrequencyradiationoriginatingfromovershootandringingontheselines.
Ifdielectriclayersarethickcomparedtothelinewidth,routegroundtracesbetweenthesignallinestoincrease
shielding.This
isespeciallyimportantifonlytwolayerboardsareused(seeFigure 14).
Bad: Excessive Radiation Good: Radiation terminated
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Figure 14: Terminating radiation of signal lines
1.6.2.3 Decoupling Capacitors
Useasufficientnumber ofdecoupling capacitorsinparallelbetween powerandground nets. Small size,small
capacitance types reduce high-frequency emissions. Large size, high capacitance types stabilize low frequency
variations.It’s preferredtohavealarge numberof smallvalue capacitorsin parallel rather thanhavingasmall
number
of large value capacitors. Every capacitor has an internal inductance in series with the specified
capacitance. In addition to resonance, the capacitor will also behave like an inductor. If many capacitors are
connected in parallel,total inductance will decrease while total capacitance will increase. Figure 15 shows the
impedancedependenceofSMD
capacitors.
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Figure 15: Impedance of 0805 size SMD capacitors vs. frequency, MuRata
Ifthepowerandgroundplanearenotconnectedbyanefficientcapacitornetwork,thepowerplanemayactas
a radiating patch antenna with respect to the ground. Furthermore, ceramic capacitors come with different
dielectric materials. These materials show different temperature behavior. For industrial temperature range
applications,atleasta
X5Rqualityshouldbeselected.Y5VorZ5Utypesmaylosealmostalloftheircapacitance
ailure at low temperatures because of excessive noise
emissions from the digital part. Tantalum capacitors show good thermal stability, however, their high ESR
(equivalentseriesresistance)limits
theusablefrequencyrangetosome100kHz.
at extreme temperatures, resulting in potential system f
GPSModules-SystemIntegrationManual(SIM)(incl.ReferenceDesign) GPSFundamentals
GPS.G4-MS4-05007-A1
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u-blox ANTARIS 4 Specifications

General

Brand	u-blox
Model	ANTARIS 4
Category	GPS
Language	English