Kenwood NX-840, Руководство по обслуживанию

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(No.RA011<Rev.001>)1-15
2.4.6.3 NXDN Receiving
• For Digital Data Mode:
The demodulated signal from IC501 (Pin13) feed into baseband IC (Pin 16) for NXDN decoding.
The decoded digital data will pass to MCU through C-BUS. MCU determines whether or not to output sound from speaker by check-
ing if the data match.
• For Digital Voice Mode:
If the digital data match in MCU, the digital voice payload data will goes into Vocoder in MCU for conversion to PCM.
The PCM data will go to baseband IC through SPI input, where it will be converted to analog by DAC.
Analog voice will be filtered and finally send to audio amplifier.
Fig.14 NXDN receiver system
2.4.6.4 NXDN Transmitting
• For Digital Data Mode:
The digital data will be generated by MCU, where it wil be pass to baseband IC, through C-BUS for encoding process. The encoded
data finally will transmit through TCXO and VCO modulation.
• For Digital Voice Mode:
The analog voice from mic will go to ADC (after audio filter) to convert to PCM data.
The PCM data will send to Vocoder through SPI output.
Vocoder will convert the PCM to NXDN protocol, where it will be sent to baseband through C-BUS.
In baseband IC, the data will be encoded and finally transmit through TCXO and VCO modulation.
Fig.15 NXDN transmit system
75 43
16 13
112
IC501
IF IC
IC709 Baseband IC
C-BUS
SPI
Vocoder
C-BUS
NXDN
decoder
Audio
Output
To E-Vol
DAC
3
IC714 MCU
76 42
23
24
113
TCXO
VCO
IC709 Baseband IC
C-BUS
SPI
Vocoder
C-BUS
NXDN
encoder
Audio
Filter
From MIC
ADC
1
IC714 MCU