3.5.7 GSM transmit VCO (U1003)
The dual Tx VCO is a key component within the GSM OPLL. This VCO performance directly impacts
PLL and transmitter performance. VCO specifications refer to muRata MQW5V0C869M datasheet.
The dual Tx VCO outputs, one for Low-band GSM and one for high band, drive a resistive network that
splits the active signal into two signals: 1) the input to the active PA . this is the low loss path, and 2)
the OPLL feedback signal . this is the high loss path. See Figure 8-1 for recommended topology and
resistor values.
The losses from the VCO outputs to the PA inputs must be factored into the output chain.s power
budget. Each path includes a π-pad that introduces approximately a 3-dB loss. The low band GSM π-
pad is formed by R235 plus R232, R228, and R229; the high band GSM π-pad is formed by R236 plus
R232, R234, and R233. One leg of each π-pad is used to couple the VCO output to form the feedback
path as described below.
For a given VCO output drive level, the loss to the RTR6250 input must assure the specified input level
is achieved (-18 to -12 dBm). Large resistors included in the π- pads are used to lightly couple off the
VCO outputs to create the feedback signal.
Since the RTR6250 TX_VCO_FB pin presents fairly high impedance, an external terminating resistor is
required (R232, 51 Ω). A series capacitor (82 pF) AC couples the feedback signal into the RTR6250 IC.
3.5.8 UMTS Rx RF filter (FL1001)
An RF filter is located between the UMTS LNA and mixer. Insertion loss is important, but not as critical
as losses before the LNA. The most important parameters of this component include:
• Out-of-band rejection or attenuation levels, usually specified to meet these conditions:
- out-of-band signals - ranging from DC up to the first band of particular concern and from the last
band of particular concern to beyond three times the highest passband frequency.
- Tx-band leakage - the transmitter channel power, although attenuated by the duplexer, still
presents a cross-modulation threat in combination with Rx-band jammers. The RF filter must
provide rejection of this Tx-band leakage.
- Other frequencies of particular concern . bands known to include other wireless transmitters that
may deliver significant power levels to the receiver input.
• Phase and amplitude balance - the ZIF architecture requires well-balanced differential inputs to the
RFR6250 IC. This is accomplished by the RF filter which takes a single-ended output from the
RFL6250 IC and provides differential outputs having nominal 180° phase separation. Phase and/or
amplitude imbalance causes degraded common-mode rejection and second-order nonlinearity, so
their requirements are specified jointly.
-
±
3 degrees and
±
1 dB
- -12 to + 3 degrees and
±
0.7 dB
Of course, passband ripple and return loss are still important in all cases for the same reasons
explained in the antenna switch module and duplexer sections.
3. TECHNICAL BRIEF
- 34 -
Содержание U8500
Страница 1: ...Date February 2006 Issue 1 0 Service Manual Model U8500 Service Manual U8500 ...
Страница 20: ...3 TECHNICAL BRIEF 21 ...
Страница 32: ...3 TECHNICAL BRIEF 33 Figure 3 5 6 1 GSM PA functional block diagram ...
Страница 35: ...3 TECHNICAL BRIEF 36 Figure 3 5 10 1 Bluetooth system architecture ...
Страница 50: ...3 TECHNICAL BRIEF 51 Figure 3 10 3 2 1 PM6650 Functional Block Diagram ...
Страница 110: ...4 TROUBLE SHOOTING 111 R605 R606 receiver signal serial resistor Receiver CN600 50pin LCD connector FPCB for LCD Module ...
Страница 112: ...4 TROUBLE SHOOTING 113 R605 R606 receiver signal serial resistor CN600 50pin LCD connector CN901 C907 C911 ...
Страница 114: ...4 TROUBLE SHOOTING 115 Loud Speaker U502 U503 Amp ...
Страница 118: ...4 TROUBLE SHOOTING 119 C200 C201 for MIC serial capacitor ...
Страница 121: ...4 TROUBLE SHOOTING 122 Q404 Q403 Q402 VBATT GND ...
Страница 128: ...5 DOWNLOAD 129 5 Choose a Module Image file after clicking on the Browse button U8500 U8500 U8500 U8500 U8500 U8500 ...
Страница 132: ...5 DOWNLOAD 133 Downloading the AMSS Modem image Rebooting and waiting for a while Performing NV restore ...
Страница 134: ...5 DOWNLOAD 135 Download of Module image in progress Download process has completed successfully ...
Страница 143: ...6 BLOCK DIAGRAM 144 6 3 Interface Diagram U8500 Interface Diagram ...
Страница 145: ... 146 ...
Страница 154: ... 155 U8500 8 PCB LAYOUT ...
Страница 155: ... 156 8 PCB LAYOUT U8500 ...
Страница 156: ... 157 8 PCB LAYOUT ...
Страница 157: ... 158 8 PCB LAYOUT ...
Страница 158: ... 159 U8500 8 PCB LAYOUT ...
Страница 159: ... 160 U8500 8 PCB LAYOUT ...
Страница 166: ...9 CALIBRATION 167 Click START button U8500 U8500_ver1 1 U8500 U8500 Click U8500 ...
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Страница 194: ...Note ...
Страница 195: ...Note ...