LG LG-YD636, Service Manual

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1.2.2 Receiver ( RFR6122 )
The RFR6122 is RF RECEIVER ( LNA&MIXER, ADC CONVERTER) The characteristics of Low
Noise Amplifier (LNA) are low noise figure, high gain, high intercept point and high reverse isolation.
The frequency selectivity characteristic of mobile phone is mostly determined by LNA.
The specification of LG-YD636 LNA is described below:
Gain mode 0 Gain mode 1 Gain mode 2 Gain mode 3 Units Parameter
Cellular Cellular Cellular Cellular
Gain
16.3 4.0 -4.4 -18.0 dB
Noise Figure 1.60 5.0 5.0 20.0 dB
Input IP3 16.5 8.7 15.0 15.0 dBm
The RFR6122 IC is an RF-to-baseband receiver IC and provides the Zero-IF receiver signal path for
Cellular-CDMA reception. For this chipset, Cellular-CDMA refers to band classes 0 and 3 as defined
by the cdma2000 standard, with mobile station receivers operating between 824 and 894 MHz. The
Rx signal path includes the LNA, quadrature downconversion, and baseband functions.
Numerous secondary functions are integrated on-chip: the Rx LO generation and distribution circuits,
the UHF VCO circuits, and various interface, control, and status circuits.
The Cellular-CDMA receive signal is routed from the antenna to the RFR6122 IC via the duplexer. The
analog baseband outputs interface with one of MSM6025 devices that also provide status and control
signaling. Power reduction features controlled by the MSM6025 device (such as selective circuit
power-down, gain control, and bias control) extend handset standby time. Integrated Rx LO circuits,
ideally supplemented by the RFT6122 transmitter IC.
1.2.3 Receive RF SAW Filter
The main function of Rx RF SAW filter is to attenuate mobile phone spurious frequency, attenuate
noise amplified by the LNA and suppress second harmonic originating in the LNA.
RX RF filter has IL of 2.2dB (Max) on the average whereas the ripple of passband is about 1.0dB
(Max) and the RF signal suppression rate on transmit band is 47dB (Min).