User's Manual

Innovator CU250ATD, 250 Watt Transmitter Tray Description
Instruction Manual, Rev. 0 12
(A6-A1) 2 Stage UHF Amplifier Board, (1308784)
The 2 Stage UHF Amplifier Board, (1308784) consists of a driver stage and a parallel
connected final amplifier stage, which have a total gain of approximately
23 dB. The working point settings for the 2 Stage Amplifier Board are factory set
using the potentiometers R32 for Q2, R15 for Q1, and R24 for Q3 and should not be
altered. The input RF connects to the first amplifier stage U2, which has a gain of
approximately 14 dB. The output is split by U2 and connected to the final amps.
The final amplification circuit consists of parallel-connected push-pull LDMOS
amplifier circuits Q1 and Q3 operating in class AB each with approximately 14 dB of
gain. The board uses a power supply voltage of 28-32V. The RF transistors are
operated at a voltage of 24V generated by the voltage regulators U1 for Q1, U5 for
Q3 and U6 for Q2, which provide a separate regulated voltage to each transistor. In
order to match the LDMOS impedance to the characteristic impedance of the input
and output sides, matching networks are located before and after the amplifier
circuits. The hybrid coupler U2 splits the input to the parallel amplifiers and the
hybrid coupler U4 combines the amplified outputs. The combined output connects
through a directional coupler to J1, the RF output jack of the board. The directional
coupler provides an RF sample at J3 that is used by an external overdrive protection
circuit. The RF output of the board, when used as a driver, has an output power
level of 3 Watts maximum 8-VSB with approximately 1.8 Amps total current draw
from the power supply. The board can also be used as the final output stage in a
transmitter with the amplifier generating 6 Watts maximum 8-VSB. In the
transmitter, the output of the 2 Stage UHF Amplifier Board at J1 connects to the RF
input of the RF Module Pallet.
(A6-A2) RF Module Pallet w/Philips Transistors (1300116)
The RF Module Pallet w/Philips Transistors (1300116) is made from a RF Module
Pallet w/o Transistors (1152336). The amplifier is capable of delivering a maximum
output power of 100-Watts peak, with an amplification factor of approximately 13
dB. The amplification circuit consists of push-pull amplifier blocks V1 and V2,
connected in parallel and operating class AB. In order to match the impedance of
the transistors to the characteristic impedance of the input and output sides,
matching networks are placed ahead and behind the amplifier blocks. Transformers
Z3 and Z4 at the input to V1 and V2 and Z5 and Z6 at the output of V1 and V2 serve
to balance the input and output signals. The paralleling circuit is achieved using the
3-dB input coupler Z1 and the second part of Z1, which is the 3-dB output coupler.
The working point settings of the amplifier circuits are factory implemented by
means of the potentiometers R9, R11, and R12 and should not be altered. The
combined output of Z1 connects to the RF output jack of the board, which is cabled
to J2 the output jack of the assembly. The output of the amplifier assembly at J2
connects to the input jack J1 of the output detector board.
(A7) Output Detector Board (1308685)
The (A7) Output Detector Board (1308685) provides forward (2V=100%) and
reflected (2V=100%) power samples to the transmitter’s Control Board for metering
and monitoring purposes. R7 is the reflected power calibration pot and R23 is the
forward power calibration pot. A Forward power sample, -10 dBm, connects to J4 on
the board, which is cabled to the front panel sample jack of the tray. The RF output
of the board, typically +46 dBm, is at J2, which is cabled to J2 the RF Output Jack of
the tray.