Antenna Interface; Gsm Antenna Interface - SimCom SIM800L Hardware Design

The timing of the synchronization signal is shown below. High level of the RF_SYNC pin indicates increased
power consumption during transmission.

4.19. Antenna Interface

There are three antenna ports for SIM800L GSM antenna port named GSM_ANT, FM antenna port named
FM_ANT, The RF interface of the three antenna ports has an impedance of 50Ω.
The input impendence of the antenna should be 50Ω, and the VSWR should be less than 2.

It is recommended that the GSM antenna and the FM antenna should be placed as far as possible.

The isolations of the two antenna should be bigger than 30dB

NOTE About the RF trace layout please refer to"AN_SMT Module_RF_Reference Design_Guide".
：

4.19.1. GSM Antenna Interface

There is a GSM antenna pad named GSM_ANT for SIM800L, the connection of the antenna must be decoupled
from DC voltage. This is necessary because the antenna connector is DC coupled to ground via an inductor for
ESD protection.
The external antenna must be matched properly to achieve best performance, so the matching circuit is necessary,
the connection is recommended as following:
Module
SIM800L(MT6261)_Hardware Design_V1.01
220us
Transmit burst
RF_SYNC
Figure 45: RF_SYNC signal during transmit burst
GND
(Pin39)
RF connector
GSM_ANT
(Pin40)
GND
(Pin41)
Figure 46: GSM antenna matching circuit
577us
R101
C101 C102
47
Smart Machine Smart Decision
GSM
Antenna
D101
2016-07-07