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SkyTraq Technology, Inc. Preliminary Draft www.skytraq.com.tw
Passive ceramic patch antenna is low-cost and provides good sensitivity. 50-ohm output larger size ceramic patch
antenna with higher antenna gain can be connected directly to RF input of the module. Usually the ceramic patch
antenna and PX1100S are mounted on opposite side of the PCB to reduce possibility of picking up digital noise. To
improve signal reception performance, use larger ground plane under the patch antenna if possible; larger the ground
plane, larger the overall antenna gain. The center frequency of the ceramic patch antenna changes with ground plane
size. For optimal L1 quad constellation signal reception, the frequency bandwidth of the antenna needs to cover
1559MHz ~ 1605MHz when mounted on the PCB. It is usual to ask the ceramic patch antenna vendor to select or tune
a patch antenna that best matches the customer PCB.
Active antenna is essentially a passive antenna with built-in LNA and a coaxial cable to connect the antenna to the
module. It has the flexibility of being located remotely from the module, but requires antenna power. Active antenna
usually costs more than passive patch antenna, but the performance in low signal environments is usually better.
Active antenna with one stage LNA gain of 10 ~ 20dB and noise figure less than 1.5dB can be used with PX1100S.
POWER SUPPLY REQUIREMENT
PX1100S requires a stable power supply, avoid ripple on VCC pin (<50mVpp). Power supply noise can affect the
receiver’s sensitivity. Bypass capacitors of 10uF and 0.1uF is recommended to be placed close to the module VCC pin;
the values could be adjusted according to the amount and type of noise present on the supply line.
BACKUP SUPPLY
The purpose of backup supply voltage pin (V_BCKP) is to keep the SRAM memory and the RTC powered when the
module is powered down. This enables the module to have a faster time-to-first-fix when the module is powered on
again. The backup current drain is less than 15μA. In normal powered on state, the internal processor access the SRAM
and current drain is higher in active mode
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