ZTE Corporation ZTEMC2261 사용자 설명서
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26
MC2261
Hardware Development Guide of Module Product
Figure 5–3 Antenna Matching Circuit
.
5.2.6. PCB
D
ESIGN
C
ONSIDERATIONS
•
The antenna subsystem should be treated like any other RF system or component. It should be isolated as much as possible
from any noise generating circuitry including the interface signals via filtering and shielding.
• As a general recommendation all components or chips operating at high frequencies such as micro controllers, memory,
DC/DC converts and other RF components should not be placed too close to the module. When such cases exist, correct
supply and ground de-coupling areas should be designed and validated.
• Avoid placing the components around the RF connection and close to the RF line between the RF antenna and the module.
• RF lines and cables should be as short as possible.
• If using coaxial cable it should not be placed close to devices operating at low frequencies. Signals like charger circuits may
require some EMI/RFI decoupling such as filter capacitors or ferrite beads.
• Adding external impedance matching to improve the match to your cable and antenna assemblies is optional. Please contact
the antenna vendor for matching requirements.
• For better ESD protection one can implement a shock coil to ground and place it close to the RF connector.
5.2.7. O
THER
P
RECAUTIONS
V_MAIN_3V7 are used to supply the module. The module internally regulates these to obtain regulated voltages to supply both
the baseband and RF parts of the Module. V_MAIN_3V7 directly supplies the RDF components with 3.7V. It is essential to keep the
voltage ripple to a minimum at this connection in order to avoid phase error. Insufficient power supply voltage can dramatically
affect some RF performance such as TX power, modulation spectrum EMC performance, and spurious emissions and frequency
error.
The RF connections are 50-ohm impedance systems and are a DC short to ground. Best effort should be made to provide low
insertion loss and shielding between the external antenna and RF connections over the frequency band of interest.
5.2.8. G
ROUNDING
On terminals including the antenna, poor shielding can dramatically affect the sensitivity of the terminal. Moreover the power
emitted through the antenna can affect the application.