Tune up description 1.Circuit Diagram and Working Theory The tracker used MediaTek platform. This platform has such advantages as less spare parts, lower cost stable capability and highly sensitive receive ability etc. The chipset is MT6252A that from MediaTek, MT6252A integrated RF transceiver for multi-band GSM and GPRS cellular systems. The amplifier is RPF88162B that from Renesas Company. 1. RF Part 1.1 Function description and diagram The main function of RF circuit is to send and receive the wireless documents and also to do document communication with chipset. The diagram is as follow:
GSM850 SAW GSM900 DCS1800 Renesas PCS1900 SAW SAW Baseband MT6252A GSM850 GSM900 DCS1800 PCS1900 Figure1 RF BLOCK DIAGRAM 1.2 Output power&Power control level GSM850 Power control Transmitter Tolerances level output power 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19
(dBm)
(normal) 31 29 27 25 23 21 19 17 15 13 11 9 7 5 3 1dB 2dB 2 dB 2 dB 2 dB 2 dB 2dB 2 dB 2 dB 2 dB 2 dB 2dB 2 dB 2 dB 2 dB PCS1900 Power control Transmitter Tolerances level output power 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
(dBm)
(normal) 29 28 26 24 22 20 18 16 14 12 10 8 6 4 2 0 1dB 2dB 2 dB 2 dB 2 dB 2dB 2 dB 2 dB 2 dB 2dB 2 dB 2 dB 2 dB 2dB 2 dB 2 dB 0 dBc 1.3 Power versus time
+4 dBc _
+1,0 dBc / /
-1,0 dBc / /
-6 dBc *
-30 dBc **
lowest limit
(see <-------- (147 bits) -------->
table 1) / /
10 8 10 7056/13=542,8 ms 10 8 10 Figure 2 : Power vs time template for normal bursts
For GSM 850:
-4 dBc for power control level 16;
-2 dBc for power control level 17;
-1 dBc for power control levels 18 and 19. For PCS 1 900 MS:
-4 dBc for power control level 11;
-2 dBc for power control level 12;
-1 dBc for power control levels 13, 14 and 15.
For GSM 850:
-30 dBc or -17 dBm, whichever is the higher. For PCS 1 900 MS:
-30 dBc or -20 dBm, whichever is the higher. Table 1: Lowest measurement limit for power / time template lowest limit GSM850,
-59 dBc or -54 dBm whichever is the highest, except GSM 900 for the timeslot preceding the active slot, for which the allowed level is equal to -59 dBc or -36 dBm, whichever is the highest DCS 1 800,
-48 dBc or -48 dBm whichever is the highest PCS 1 900 2 Chipset Part The main functions for Chipset are as follows: Process documents keeping and DSP, keypad inputting, communicating With RF module, RF power controlling, PM Module controlling, SIM card interface Serial download interface and GPS .For details, please find theory diagram showed on Fig 1-2. The regular module and functions were showed comparatively on it. Figure3 Chipset circuit theory diagr