A. RF Front End
RF front end consists of Antenna Switch(FL401), dual band LNAs integrated in transceiver(U401).
The Received RF signals (GSM 925MHz
∼
960MHz, DCS 1805MHz
∼
1880MHz) are fed into the
antenna or mobile switch. An antenna matching circuit is between the antenna and the mobile switch.
The Antenna Switch (FL401) is used to control the Rx and TX paths. And, the input signals VC1 and
VC2 of a FL401 are connected to DCSSEL(GPO_9) and GSMSEL(GPO_11) ports of U101 to switch
either TX or RX path on. When the RX path is turned on, the received RF signal then feeds either Rx
_900_RF or RX_1800_RF path controlled by GSM-RX and DCS-RX respectively. This Rx_900_RF
path contains one SAW filter, followed after the Antenna Switch (FL401), to filter any unwanted signal
apart from the DCS RX band. And, the RX_1800_RF path is the same case.
The logic and current for Antenna Switch is given below Table 3-1.
Table 3-1 The logic and current
<0.1 mA
0 V
0 V
GSM/DCS RX
10.0 mA max
0 V
2.7 V
DCS TX
10.0 mA max
2.7 V
0 V
GSM TX
Current
VC2
VC1
These two paths are then connected to the LNAGSMIN (#11) and LNADCSIN (#13) of
CX74017 (U401), respectively. A low-noise bipolar RF amplifier, contained within the U401,
amplifies the RF signal. The RF signals from the front-end pass to the receiver mixers
within the U401 device.
- 16 -
In direct conversion receiver there is only one mixer that is down-converting received RF signal to BB
signal directly. The gain of the mixer is 40dB at high gain mode and 22dB at low gain mode.
The Rx gain setting is done in the AGC algorithm. The nominal gain of the receiver is set as a
function of the expected signal strength at the antenna input so that a desired level is reached at the
Rx I/Q. 7 blocks in the receiver chain have variable gains, LNA, Mixer, LPF1, VGA1, gmC Filter,
Auxiliary gain control and VGA2. The gain settings can be adjustable via 3-wire bus control lines.
The baseband signals pass via integrated low-pass filters to the baseband A/D converters.
The remainder of the channel filtering is performed by the baseband chipset. The demodulator
contains switches to maintain the sense of the baseband I/Q outputs with respect to the incoming RF
signal on both GSM900 and DCS1800.
B. Demodulator and baseband processing
3. TECHNICAL BRIEF
Содержание G3100
Страница 32: ... 34 3 TECHNICAL BRIEF Figure 3 20 TX IQ Signal Figure 3 21 RX IQ Signal ...
Страница 40: ... 42 Figure 3 26 1 Voice band circuit diagram Headset Hands free kit part 1 3 TECHNICAL BRIEF ...
Страница 42: ... 44 Figure 3 27 AD6521 circuit diagram 3 TECHNICAL BRIEF ...
Страница 73: ... 75 4 3 8 Receiver RF Level Figure 4 1 Test Points of Rx Level 4 TROUBLE SHOOTING ...
Страница 74: ... 76 4 3 9 Transmitter RF Level Figure 4 2 Test Points of Tx Level 4 TROUBLE SHOOTING ...
Страница 81: ... 83 The Receiver part Circuit Diagram C203 C207 C206 4 TROUBLE SHOOTING ...
Страница 87: ... 89 R202 MIC201 R204 C204 C201 R208 R206 C208 Q203 4 TROUBLE SHOOTING ...
Страница 93: ... 95 Test SIM Connector Check J301 4 TROUBLE SHOOTING ...
Страница 97: ... 99 J201 R240 C234 L201 R241 4 TROUBLE SHOOTING U205 U203 U204 ...
Страница 101: ... 103 CN302 U203 U204 4 TROUBLE SHOOTING ...
Страница 102: ... 104 U205 4 TROUBLE SHOOTING ...
Страница 104: ...5 DISASSEMBLY INSTRUCTION 106 3 Detach the rest components as shown below Figure 5 3 Detaching the rest components ...
Страница 108: ...3 Press Start and Wait until Erase is completed 110 1 Press Start 2 Confirm completion 6 SOFTWARE DOWNLOAD ...
Страница 117: ... 119 9 PCB LAYOUT 9 1 Rear Part ...
Страница 118: ...9 2 Front Part 120 ...
Страница 124: ... 126 11 2 Standalone Test Equipment Setup GSM Test Equipment Power Supply PC JIG RS 232 Cable Phone 11 STAN ALONE TEST ...
Страница 134: ... 137 13 EXPLODED VIEW REPLACEMENT PART LIST 13 1 Exploded View ...