Fig.4:The IF Synthesiser (RX)
DIV
13
LOOP
FILTER
DIV 180
IC201 LMX2331L IF-PLL
PHASE
COMPARATOR
23-24
PHASE
DIFFERENCE
(CURRENT)
PHASE
DIFFERENCE
(VOLTAGE)
13MHz
CLK
8
1Mhz
1Mhz
GND
IC300
32
33
34-35
DIV3
18
16
180Mhz
180Mhz
D303B
D303A
DIV2
To RX Demodulator
540Mhz
31
PUPLO2
GSM_TX
GSM_TX =”1”= 180Mhz
GSM_TX =”0”= 270Mhz
2
The RX IF Synthesiser
The IF synthesiser (IF- PLL) is contained within IC201 - LMX2331L. It is used to
tune the 540Mhz TX/RX IF oscillator inside IC300.
The 540Mhz oscillator output is first divided down by a factor of 3 within IC300.
This is achieved by an internal pre-selectable divider, which is set by the signal
GSM_TX from IC27 #23. In receive mode the signal is high, which sets the divider
to 3 so therefore the 540Mhz is reduced to 180 Mhz, which is output on pins #23
and #24. This signal is then fed to #16 of IC201, where it is then divided down by
a factor of 180 to give a 1Mhz signal.
A 1Mhz reference signal derived from the 13Mhz clock is input to the phase
comparator and compared with the 1Mhz signal derived from the 270Mhz signal.
The phase comparator then derives a current phase difference of the two signals
and outputs it to the loop filter on pin #18 of the device.
The loop filter (C218, C219, C220,R202,R204 & L205) then uses the current
phase difference to produce a voltage phase difference and outputs this to the
Varactor network (D303 A/B).
The Varactor network and circuit at #33-35 form part of the 540Mhz oscillator
circuit, which is tuned by the phase voltage applied to the network.
The control signal:
PUPLO2
from IC27 #26 is used to switch the 540Mhz signal
ON or OFF.
Содержание DB2000
Страница 1: ...DB2000 Service Manual Help ...
Страница 3: ... ...
Страница 4: ...Important One incorrect adjustment may result in the need for many more and result in extra 0 1 2 2 ...
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Страница 83: ...Fit Antenna INSERT AND SCREW THE ANTENNA INTO THE ASSEMBLY ...
Страница 106: ...Part 5 Test Signals Fig 3 4 V_G_LNA Pg 3 5I TP300 Fig 3 5 V_P_LNA Pg 3 5J TP301 Fig 3 6 RX_ON2 Pg 3 16G TP405 ...
Страница 107: ...Fig 3 7 GSM_LNA Pg 3 3I TP419 Fig 3 8 PCN_LNA Pg 3 3J TP420 Fig 4 9 TCXO Pg 2 H11 TP413 ...
Страница 108: ...Fig 4 0 GSM Rx I Q s Pg 3 E F15TP406 7 Fig 4 1 PCN Rx I Q Pg 3 E F15 TP406 7 Fig 4 2 GSM_TX Pg 1 1I TP403 ...
Страница 109: ...Fig 4 3 PCN_TX Pg 1 1J TP417 Fig 4 4 3V_G_TX Pg 1 4I TP100 Fig 4 5 3V_P_TX Pg 1 4J TP101 ...
Страница 110: ...Fig 4 6 GSM_ON Pg 1 2K TP402 Fig 4 7 PCN_ON Pg 1 1K TP415 Fig 4 8 PRE_ON Pg 1 4J TP416 ...
Страница 112: ... I Q ...
Страница 113: ...Fig 4 14 V_ERROR PCN Pwr Lvl 7Pg 1 16I Fig 4 15 300khz Charge Pump Pg 1 Log 9G ...
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