Hitachi EC701HP Operation Manual page 16

Section 1 - Introduction (UHF Digital TV Transmitters)
E-Compact - Air Cooling - ATSC - High Power
Both (I) and (Q) modulated carriers are routed into the IF/UHF up-converter. The local oscillator is
a synthesized time-based PLL via an internal VOCXO (Voltage / Temperature Oven Controlled
Crystal Oscillator). This oscillator can receive external reference one among 6 possibilities;
(External 1PPS GPS, Internal 1PPS GPS, External 10MHz or Input Transport Stream).
The on-channel modulated signal is routed to the RF amplifier, a class A highly linear amplifier
with enough head room to accommodate future signal amplitude expansion during the non-linear
pre-correction process.
The exciter output delivers a 100mW max RF output level, (+20dBm) at the desired UHF channel,
driving the RF power amplifiers line-up. The overall RF output power is kept over control via an
internal power control loop ALC.
The power sensors for direct and reverse power are integrated also on this same PC Board;
allow the power control feature for a several different types and models of transmitters. A sample
of the of the RF signal delivery to the load is necessary to be present, so the external loop to
control the RF power is closed. (External Power Control Loop).
The Master Control Unit (MCU) of the unit is embedded in the exciter. The MCU interacts with all
functionality present within the equipment. It further interfaces externally via a keypad and an
LCD display.
The MCU receives information proceeding from several modules, as the DTV modulator, Up-
Converter, RF amplifiers, RF samples and the administration of passwords. Via keypad it is
possible to read and program the power level delivered by the transmitter. Major changes on the
transmitter configuration are possible with factory assistance.
The Digital Exciter interacts with the HITACHI proprietary software (GUI8001) that performs the
implementation of linear and non-linear pre-correction as required; the software also conducts
measurements on the demodulated signal, such as MER and power spectrum readings,
among others.
ATTENTION: In the event of any changes being required in the settings of the
equipment, the Service Department of Hitachi Kokusai Linear should be consulted
for further information on the procedures to be adopted .
Manual Rev. 0.1 - February 2018
Figure 1-4
Front view - Digital Exciter
1-9