DP770 Service Manual
process audio signal and digital signal. The audio amplifier TDA8547TS is used to amplify the analog audio
signal.
DSP processes digital signal (i.e audio signal encoding/decoding, digital I/Q signal decoding, digital audio
signal processing). The AD9864 converts and processes the RF IF, and sends un-demodulated serial
digital signal to the DSP for processing. Then DAC5614 converts the digital signal output by DAS to analog
signal.
Figure 3-8 Audio Section Diagram
• D
iagram of Signal Flow
The microphone converts the audio signal into electrical signal, which is amplified by PGA of the codec and
then sent to ADC of the codec for sampling. After digital audio processing, the signal is output DSP for
processing. Then the signal is sent to DAC (TLV5614), which converts the signal to modulation signal. After
modulated and amplified in the RF module, the signal is sent out from the antenna.
The RF signal received by the RF module is converted to digital by ADC (AD9864), and is then sent to DSP
for modulation and processing. Then the digital signal is sent to the digital audio processor of the codec for
digital audio processing, and is then converted into analog audio signal by DAC of the codec. Finally the
signal is amplified by the external audio amplifier (TDA8547TS) to drive the speaker.
• System Peripheral Function Unit
The system peripheral consists of analog/digital converter module, vocoder encryption module, TF card
interface module, display module, key detection module and acceleration sensor module. These modules
are used to achieve human-radio interaction, state detection, communication encryption and feature
extension. The analog/digital converter is used for voice signal strength detection, power supply detection,
temperature detection, so as to realize VOX, low battery warning and temperature control. The acceleration
sensor is used to detect tilted state, realizing mandown function. The TF card module interface is used for
communication encryption, to provide communicate security.
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