Motorola Cleartone CM5000 Basic Service Manual page 26

12
Voice CODEC (ACELP)
Transmit analog voice data is converted to the digital signal by the linear CODEC and fed to the
Voice CODEC DSP.
The Voice CODEC DSP compresses the input digital signal by ACELP algorithm to the coded voice
data. And the data is fed to the Channel CODEC DSP.
Received digital voice data is fed to the voice CODEC DSP from Channel CODEC DSP as coded
voice data.
The Voice CODEC DSP expands the coded voice data and fed to the linear CODEC. The digital sig-
nal is converted to the analog signal by the linear CODEC and output as analog signal.
Frequency Compensation
The Channel CODEC DSP calculates frequency error between the radio and base station (Master
station in DMO). It controls the VC-TCXO by DAC so as to minimize the frequency error. The VC-
TCXO works as time base reference of the radio.
Transmit Power Control and Linearization
The Channel CODEC DSP controls the output power by the DAC based on the receive signal
strength and broadcast information from the base station.
Also the DSP calculates so as to minimize the distortion of the transmitter and carrier leak and con-
trols the Cartesian Loop by DAC.
VC-TCXO
The reference signal for the PLL synthesizer is generated by VC-TCXO. The oscillation frequency of
the 13 MHz reference signal is fine controlled by Channel CODEC DSP. The frequency error
between the Radio Terminal and TRBS is detected and error correction signal is generated by DPS.
And the error correction signal is fed to Voltage Control circuit of the TCXO to make fine frequency
tuning.
Interface Unit
The Main unit has analog interface circuit and digital interface circuit for external interface.
Digital Interface
Digital interface is connected to the connector J902 and J904 at the rear of the Main unit. Those
connectors are combined in the one connector, but electrically independent. One is RS232 level
interface, and the other is 0 V / 3 V interface level.
The RS232 level serial communication is connected to the 7 pins connector (J904) at the rear of the
Main unit. This connector is used for the programming of the radio parameter, AT command control,
data output for the log etc.
The usage is dependant on the setting in Native Programmer, which is described in Pro-
0 V / 3 V level serial communication is connected to the 20 pins connector (J902). This connector is
used for same purpose. Features of those connectors are configured by programming. When con-
necting the external equipment with the 20 pins connector (J902), appropriate level converter is
required.
CM5000 Mobile Repeater/Gateway - Basic Service Manual
gramming Manual (part number 6866539D46).
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