The offset mixer down converts the feedback Tx RF signal using LO to generate a IF modulating
signal. The IF signal goes via external passive bandpass filter to one port of the phase detector.
The other side of the phase detector input is LO signal. The phase detector generates an error
current proportional to the phase difference between the modulated signal from the offset mixer
and the reference signal from the LO.
The error current is filtered by a second order low-pass filter to generate an output voltage which
depends on the GMSK modulation and the desired channel frequency. This voltage controls the
transmit VCO such that the VCO output signal, centered on the correct RF channel, is frequency
modulated with the original GMSK data. The OPLL acts as a tracking narrowband band pass filter
tuned to the desired channel frequency. This reduces the wideband noise floor of the modulation
and up-conversion process and provides significant filtering of spurious products.
B. OPLL
The CX74017 includes a fully integrated UHF VCO with an on-chip LC tank.
A single sigma-delta fractional-N synthesizer can phase lock the local oscillator used in both
transmit and receive path to a precision frequency reference input. Fractional-N operation offers low
phase noise and fast setting times, allowing for multiple slot applications such as GPRS.
The generated frequency is given by the following equation.
(3) Synthesizer Part
- 19 -
3. TECHNICAL BRIEF
R
f
FN
N
f
ref
VCO
+
+
=
22
2
5
.
3
where : = Generated VCO frequency
N = N-divider ratio integer part
FN = Fractional setting
R = R-divider ratio
= Reference Frequency
VCO
f
VCO
f
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 ...