U8185
Maintenance Manual
9 Principles and Failure Analysis
Issue 1.0 (2012-03-23)
Huawei Proprietary and Confidential
Copyright © Huawei Technologies Co., Ltd.
45
transmitted from the ANT end to the duplexer and then sent out through the antenna. The
duplexer's Rx and Tx ends are isolated, preventing transmission signals from interfering to
receiving signals and thereby affecting antenna sensitivity.
Figure 9-11
Receiving circuit
The reception channel includes the antenna, duplexer, RTR6285A's internal LNA and receiver,
and external single-ended to differential filter. Reception channel: Signals are received from
the antenna > After frequency selection and filter ing on the duplexer, receiving signals are
transmitted to the RF receiver > Signals are amplif ied by the LNA > Signals are processed by
the single-ended to differential filter > Signals are amplified > Signals are modulated by
Quadrature Downconverter and become I/Q signals > After analog-to-digital conversion
(ADC), signals are transmitted to CPU for processing.
Troubleshooting Process
Failure: No transmission; the phone cannot initiate or receive a call, or access the network.
Solution: