User Manual

SECTION 2: FACTORY TEST PROCEDURE
IP4HPVGPS-MRFCCRpt.doc Page 19
The plot in Figure 2-4 is the same as before but now the scope is in the peak detect acquisition mode.
After the mobile radio detects a step response in the RSSI (caused by a down-link transmission), the
radio's microcontroller waits an amount of time equal to the programmed value of the "carrier detect delay
time" then instructs the modem to look for frame sync. When the microcontroller instructs the modem to
look for frame sync, it asserts the modem's CS line (active low). In this plot, the modem's CS line can be
seen to transition low approximately 3 milliseconds after the base station's transmitter has come up to full
power.
Figure 2-4: Downlink Timing Characteristics Plot in Peak Detect Acquisition Mode
The recovered modulation should be centered at approximately 2.5 VDC and should have an amplitude
of approximately 800 mV peal-to-peak as indicated in the plot above.