N1_Hardware_User_Guide
Copyright © Neoway Technology Co., Ltd
53
Figure 7-9
Passive GPS antenna design reference
LNA
Passive
Antenna
N1
33pF
50
Ω
impedance line
It is recommended to add an ESD protection diode to the antenna interface in an environment with great
electromagnetic interference and other applications with bad ESD. The ESD protection diode must have
ultra-low capacitance (lower than 0.5 pF). Otherwise, it will affect the impedance of the RF loop or result
in attenuation of RF signals. RCLAMP0521P from Semtech or ESD5V3U1U from Infineon is
recommended.
On the PCB, keep the RF signals and RF components away from high-speed circuits, power supplies,
transformers, inductors, the clock circuit of single-chip host, etc.
7.4 FM RF Design and PCB Layout
FM antenna has been matched inside the module. Connect the FM antenna pin to the FM antenna through
a 50Ω RF impedance line. For the antenna layout, refer to the design manual of the component.
FM signal can be received through the headphone cable, which is used as the FM antenna. Connect the
FM antenna to the headphone GND pin though a 4700 pF capacitor. Figure 7-10 shows the reference
design of the headphone circuit that supports FM function.
