Comtech EF Data CST-5005 - Manual (Page 87)

CST-5005 C-Band Satellite Terminal Theory of Operation
Rev. 1 5–17
5.6.1 Specifications
Input Frequency 70 MHz (± 18 MHz)
Input Connector SMA Female
Input Impedance 50
Ω
Input VSWR 1.3:1
Output Frequency 5845 to 6425 MHz
Output Connector SMA Female
Output VSWR 1.5:1
1 dB Compression +37 dBm
1st RF Local Oscillator Input
Frequency 1112.5 MHz
Level +13 dBm
Connector SMA Female
Return Loss 10 dB
Impedance 50
Ω
2nd RF Synthesizer Input
Frequency 4662.5 to 5242.5 MHz, in 125 kHz steps
Level +4 dBm
Connector SMA Female
Return Loss 10 dB
Impedance 50 Ω
5.6.2 Theory of Operation
The RFT-505 up converter utilizes a dual conversion process to convert from a baseband
70 MHz IF signal to the output RF frequency band. The first conversion requires an IF
Local Oscillator frequency input at 1112.5 MHz from the synthesizer module.
The output of the first mixing process is at a frequency of 1182.5 MHz. The 1182.5 MHz
output is applied to the second mixer which mixes with the synthesizer frequency input.
The M&C board controls the frequency selection of the synthesizer and the U/C
attenuator.
The M&C board also interpolates the factory preset compensation data that is stored in
an EEPROM inside the up converter. This data allows the M&C board to command and
compensate the up converter’s output power, ensuring proper output power levels over
the entire frequency and temperature range.
The up converter synthesizer output frequency band is from 4662.5 to 5242.5 MHz, in
125 kHz steps.
The output of the second mixer is the desired RF frequency band of 5845 to 6425 MHz.