User's Manual

Smart Machine Smart Decision
SIM868_Hardware_Design_V1.00 47 2016-06-20
It have according to reference trace and matching circuit testing all FCC items,and all items satisfy FCC
requirements.Only the reference trace and matching circuit is certified, antenna design must refer to it, any
other deviations require testing Class II applications as required by FCC. The certified matching circuit as
following:
The external antenna must be matched properly to achieve best performance, so the matching circuit is necessary,
the connection is recommended as the following figure:
Figure 39: GNSS passive antenna matching circuit
The components R101, C101 and C102 are used for antenna matching, the components’ value only can be got
after the antenna tuning. Normally R101 is 0Ω, C101 and C102 are not mounted.
Figure 40: GNSS active antenna matching circuit
Active antennas have an integrated Low-Noise Amplifier (LNA). VCC_ANT is needed on customer’s application
board for the active antenna power input, as shown in Figure 40. The inductor L101 is used to prevent the RF
signal from leaking into the VCC_ANT pass and route the bias supply to the active antenna, the recommended
value of L101 is no less than 27nH. R102 can protect the whole circuit in case the active antenna is shorted to
ground.