User's Manual

Innovator CU0TD-1/CU0RD-1 – CU4TD/CU4RD ATSC Board Descriptions
Transmitter/Regenerative Translator
Instruction Manual, Rev. 2 111
(A6) Amplifier Assembly (1316313) Used in CU0TD/RD-1
The (A6) Amplifier Assembly (1316313) is made up of (A6-A1) the 1 Watt UHF Amplifier
Board (1310282 and the (A6-A2) the BL881 Single Stage Amplifier Board (1314882).
The assembly has approximately 35 dB of gain.
(A6-A1) 1 Watt UHF Amplifier Module (1310282)
This board is normally operated at a power of 200 mW pk sync or lower. It consists of
two AH202 MMICs operating in parallel. The board is powered by +12 VDC and has no
adjustments. The amplifier module has a gain of approximately 17 dB.
(A6-A2) BLF881 Single Stage Amplifier Board (1314882)
This board consists of a single stage amplifier operating at +48 VDC. The board has an
overall gain of about 16 dB. The input to the board passes through a 3 dB attenuator
consisting of R11-R13, and then is applied to the gain stage, which consists of a single
LDMOS transistor Q1 operating in Class AB. The bias voltage for the transistor is
generated through the voltage regulator U1, and is adjusted using pots R2 and R3. The
Diode CR1 provides temperature compensation for the transistor. The transistor will
output over 40 Watts pk sync, but is typically used in a driver application at much lower
output powers. The Directional Coupler U2 provides a 20 dB down sample of the RF
output at the SMA Jack J4.
(A6) Amplifier Assembly (1312566) – Used in CU0TD/RD-2
The (A6) Amplifier Assembly (1312566) is made up of (A6-A1) the 2 Stage UHF
Amplifier Board (1308784) and (A6-A2) the RF Module Pallet, Philips, High Output
(1309580). The ALC Board (1315006) is also part of this assembly. The assembly has
approximately 36 dB of gain.
(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 located on (A5) the ALC Board. The RF
output of the board is being used as a driver and has a level of 3W maximum 8-VSB. At
this power level the board draws approximately 1.8A total from the power supply.