1-8 (E)
WLL-CA55
1-5-2. DPR-255 Board
The DPR board encodes the video and audio signals to an
MPEG stream, performs OFDM modulation, and then
transfers the modulated signal to the transmitter.
Either the 4:2:2 parallel digital video signal from the VPR
board or the SDI signal transferred from the external unit
to the SDI IN/VBS IN connector is the input video signal.
The signal that has been input into the VBS IN/SDI IN
connector passes through the electronic switch IC10 on the
motherboard MB-1022, and is sent to the DPR board (SDI
signal) or to the APR board (VBS signal).
On the other hand, either serial digital audio signal from
the VPR board or the serial digital audio signal embedded
in the SDI signal is the input audio signal.
The intercom signal from the camera, that is processed in
the APR board, and the command from the IF board are
multiplexed with the MPEG stream.
The FPGA IC200, MPEG encoder module, and the OFDM
modulator IC307 perform the main processing.
OFDM: Orthogonal Frequency Division Multiplexing
Video Signal
The SDI signal is converted to 10-bit parallel data by the
SDI receiver IC104. Either the converted data or the 4:2:2
data from the VPR board is selected in IC105, IC106, IC2
and IC3, and then transferred to the FPGA. When the DC
LINE switch of the power supply block is set to the central
ON position, the signal from the SDI input is selected.
While the switch is set to the left ON position, the signal
from the VPR board is selected. A TRS based on synchro-
nization signals (CA CF, CA VD, and CA HD) is added to
the 10-bit digital video signal that is input into the FPGA,
and the upper 8 bits of the signal are input into the MPEG
encoder module.
To display a unit’s alarm on the camera viewfinder, the Y
signal and characters are merged in the FPGA. The merged
Y signal is D/A converted in IC603 and returned to the
camera through the APR board.
TRS: Timing Reference Signal
Audio Signal
The audio signal embedded in the SDI signal is extracted
in the FPGA. The channel 1 and channel 2 audio data of
Group 1 in the SDI signal are extracted. Either the extract-
ed SDI audio signal or the audio signal from the VPR
board is selected in the FPGA, and then transferred to the
MPEG encoder module. The selection is carried out with
the DC LINE switch in the same way as the video signal.
MPEG Encoding and OFDM Modulation
Video/audio signals that have been input into the MPEG
encoder module are compressed and multiplexed to an
MPEG stream. The MPEG stream is input again into the
FPGA.
The intercom analog audio signal transferred from the
APR board is A/D converted in IC603 and transferred to
the FPGA. It is then added to the MPEG stream together
with the command from the IF board and a wireless ID.
This merged MPEG stream is input into IC307 and
modulated to the OFDM signal. The IC307 output signal is
transferred to the transmitter as a 9.14 MHz IF signal
whose frequency band is limited by the bandpass filters
FL401 and FL402. The signal is then converted to a 2.4
GHz set frequency, and transmitted from the omnidirec-
tional antenna.
