Axcera CHV400BTD, Technical Manual, Page: 59 / 87

Innovator CHV400BTD ATSC Transmitter Board Descriptions
Technical Manual, Rev. 0 55
other High output of U4B is connected to U12B pin 5 whose output at pin 7 goes High.
This high connects to the gate of Q8 Biasing it On. With Q8 On, a low is connected to
J7-2, Modulation Loss, which is wired to the Control Board for control and monitoring.
±12 VDC, +6.8 VDC, and VREF needed to operate the Board
The ±12 VDC connects to the board at jack J7. The +12 VDC connects to J7 pins 5 and 6
and is filtered by L10 and C25 before it is applied to the rest of the board. The
-12 VDC connects to J7 pin 8 and is filtered by L9 and C23 before it is applied to the rest
of the board.
Two reference voltages are needed for the operation of the pre-corrector circuits. One
+12 VDC input is split by R103 and R104. The split +12 VDC output through R103
connects to the Zener diode VR1, which generates the +6.8 VDC output that is used in the
pre-corrector stage. The split +12 VDC output through R104 connects to the diodes CR15
and CR16 that supply a .9 VDC reference output voltage, VREF, which provides
temperature compensation for the two diodes in each of the in phase and quadrature pre-
corrector stages.
J6
IF Input
Mixer Mixer
J7
RF Output
1 GHz
TCXO
Fract-N PLL
Integer-N PLL
Integer-N PLL
10 MHz
TCXO
External
10 MHz
Detection
J10
External
10 MHz Input
VCO 1
VCO 2
Band Switching
from Ext Control
1 GHz
1.1-1.9 GHz
(A4) Frequency Agile Upconverter Board (1309695)
The board takes a 44 MHz or 36 MHz IF signal and converts it to a TV channel in the
range of 54-860 MHz. The IF input signal, (≈-8dBm level), is connected to J6 on the
board. The IF first passes through a frequency response pre-corrector, consisting of
R145, C188, R 146 and C189. The pre-corrector circuit compensates for any response
variation in the ceramic filter used to pick the appropriate conversion sideband. The
pre-corrected signal is then converted to a second IF centered at 1044 MHz using U16,
U18 and associated components. The signal is next applied to a second mixer, U15,
where it is converted to the final RF channel frequency. The signal is then sent to a low
pass filter that removes unwanted conversion products above 1 GHz, amplified by U21
passed to another low pass filter that removes unwanted conversion products above 1
GHz, amplified by U20 and connected to J7 the RF output jack for the board (≈-3dBm
level).