Sony HKCU-FP1, Руководство по обслуживанию

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2-15 (E)
HXCU-100
DPR-300 Board
The DPR-300 board has two blocks: one is for digital triax transmission and the other is for video signal
processing.
[Digital Triax Transmission Circuit]
The transmission circuit consists of an FM signal transmitter/receiver for the standby intercom/tone/sync
signals, and an OFDM signal transmitter/receiver for the video/audio/trunk signals and commands. This
circuit has a function to monitor the receiver operation status for the OFDM signal transmitter/receiver
control and a function to detect the length of the connected triax cable.
.
In the FM receiver, the FM signal (carrier frequency 1.4 MHz) is extracted from the RF signal sent from
the camera by the MPX fi lter and BPF, and is demodulated by IC1502. The demodulated signal is
separated into standby intercom signal (CAM to CCU) and tone signal (16.38 kHz) by the LPF (7 kHz)
and HPF (14 kHz). The tone signal is used to control the main power supply (180 VDC) to the camera.
In the FM transmitter, the standby intercom signal (CCU to CAM) and the sync signal are switched, and
the selected signal is FM-modulated with a carrier frequency of 1.0 MHz and is then sent to the CCU.
The standby intercom signal (CCU to CAM) is transmitted during the standby state, and the sync signal
is transmitted while the main power is turned on.
.
The OFDM signal receiver circuit consists of two blocks: one is for the F1/F2/F3 low bands and the
other is for F4/F5/F6 mid bands to support six waves F1 to F6 for transmission of video/sub video/MIC/
INCOM/command signals.
The low-band receiver circuit removes low-frequency noise from F1 to F3 signals that are output from
the LPF side of the MPX
fi lter by the HPF (0.9 MHz), and ampli fi es the signals by the low-noise ampli-
fi er, and selects them for each band by the BPF for individual processing.
The levels of the selected F2 and F3 signals are regulated by the step gain ampli fi er (that automatically
switches ampli fi er gain to four steps according to input signal level) and the AGC ampli fi er. Then the
signals are converted to signals with a center frequency of 36 MHz by the mixer circuit.
Since the AGC ampli fi er does not function in the F1 band, the F1 signal processing circuit con fi guration
is different from that for F2/F3 signals. In the F1 signal processing circuit, the F1 signal is input to the
step gain ampli
fi er (IC3402) and then to the mixer circuit. The F1 signal is converted to a signal with a
center frequency of 36 MHz, and the signal level is regulated by the AGC ampli fi er.
The converted OFDM signals F1, F2, and F3 (36 MHz center frequency) are converted to TS data by
the demodulator ICs (IC3404, IC3504, and IC3604), and the serial TS data is output to the video signal
processing circuit.
The mid-band receiver circuit ampli fi es the F4 to F6 signals that are output from the BPF side of the
MPX fi lter by the low-noise ampli fi er, and selects them for each band by the BPF for individual pro-
cessing. Since attenuation in the cable transmission becomes large in the mid signal band, this circuit
has a function to switch the low-noise ampli
fi er gain to two steps according to the transmission dis-
tance.
The selected F4 to F6 signals are processed in the same circuit con fi guration as for the F2 and F3 sig-
nals.
.
The OFDM signal transmitter circuit consists of two blocks: one is for F7
+
F9 bands and the other is
for F8 band to support three waves F7 to F9 for transmission of return video/prompter video/ INCOM/
PGM/command signals.
The video signal processing circuit generates OFDM signals with D/A conversion. However, because
the clock frequency is 183 MHz, this circuit generates OFDM signals with low frequencies (26
+
46
MHz and 36 MHz) but not with direct (F7
+
F9) and F8 frequencies, and then converts them to signals
with (F7
+
F9) and F8 frequencies by the mixer circuit. Then the converted OFDM signals are mixed
by the respective output drivers and are output to the camera. Since attenuation in the cable transmis-
sion becomes large in the F7 to F9 signal bands, this circuit has a function to switch the output signal
level to four levels by the gain control ampli
fi er and ATT according to the transmission distance.
This digital triax transmission circuit is provided with a transmission cable length detection function for
transmission distance-based control, a mixer circuit, and a 4MHz clock generator for the OFDM signal
demodulation IC.