Справочник Пользователя для IP Mobilenet LLC M32450-25

 

 

M32450-25-FCCRpt.doc  

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Figure 2-2 displays another oscilloscope plot of an up-link data message from the mobile to the base 
station.  As in the last plot, channel 1 is connected to the base station's RSSI (J5-12), channel 2 is 
connected to the base station's recovered modulation test point, and channel 3 is connected to the base 
station's modem chip select line (U16-13).  The scope's acquisition mode is now in the peak detect mode.  
This enables the base station's modem CS (Chip Select) line to be viewed. 
 
 

Figure 2-2: Another Oscilloscope Plot of an Uplink Data Message 

 

 
 
 
The base station's microcontroller, upon detecting a step response in the RSSI (caused by the mobile 
radio's transmitter coming up to power), waits a period of time equal to the programmed value of the base 
station's carrier detect delay time.  The microcontroller then instructs the modem to search for the modem 
synchronization preamble.  When the base station instructs the modem to look for sync tones, the 
modem's CS line transitions low.  This can be seen in the above plot.  Approximately 10 milliseconds after 
the mobile radio's transmitter causes a step increase in the base station's RSSI, the CS signal goes low 
momentarily.  As can be seen, the sync tones are stable by this time and the modem quickly establishes 
synchronization.