Comtech EF Data MIDAS Version 4.X NMS Configuration User Manual
Page 140
MIDAS 4.X NMS Configuration, Rev. 6
A-8 Frequency
Translations
IF to Ku-Band
Frequency Inversion
Normally there is no frequency inversion between the IF (70 MHz) and the RF (C-Band
or Ku-Band). If there were a frequency inversion between IF and Ku-Band, the IF to Ku-
Band conversion is altered slightly. The IF Frequency is subtracted instead of added. In
the example of a Ku-Band frequency of 11.72825 GHz, the IF frequency would be 61.75
MHz, 8.25 MHz below the IF center of 70 MHz.
RF =
Transponder RX Center + 70 MHz – IF
(1720 + 70 – 61.75 = 11728.25 MHz)
Also, in this case, the IF to L-Band formula changes, and the conversion factor is:
Conversion Factor =
Transponder RX Center - 10750 MHz + 70 MHz
(11720 MHz - 10750 MHz + 70 MHz)
Conversion Factor =
1040 MHz
The usage of the conversion factor is:
L-Band = Conversion Factor – IF Freq
or
IF = Conversion Factor – L-Band
C
C
-
-
B
B
a
a
n
n
d
d
F
F
r
r
e
e
q
q
u
u
e
e
n
n
c
c
y
y
T
T
r
r
a
a
n
n
s
s
l
l
a
a
t
t
i
i
o
o
n
n
s
s
The following parameters are configurable for C-Band:
Satellite - Downlink
Factor
Equivalent to LNB LO (Low Noise Block Converter Local Oscillator frequency).
Common C-Band LO’s include 5.15 GHz & 5.76 GHz)
Satellite -
Translation
Frequency difference between the Transponder TX Center and the Transponder RX Center
(C-Band Default = 2.225 GHz)
Satellite - Hi Side
Injection
High Side Injection is where the LNB LO frequency is higher than the RX RF frequency and
the difference is used to convert to L-Band (C-Band default = ON/High side injection)
Transponder - TX
Center
TX center frequency the C-Band transponder
Transponder - RX
Center
RX center frequency the C-Band transponder
This example shows a 36 MHz C-Band transponder with the default case of high side in-
jection, which results in frequency inversion. If low side injection is specified, use the
Ku-Band example, substituting C-Band frequencies in the examples. Figure A-6 shows
the relationship between the downlink RF frequencies and the corresponding L-Band IF
frequencies for the first transponder of a satellite.