The VHF/UHF transponder is the main payload to provide two -way radio communications. The VHF uplink has a frequency of 145.990 MHz, the UHF downlink band has a frequency of 435.200 – 435.250 MHz. The transponder consists of amplifiers, filters, mixers and AGC (Automatic Gain Control) stages. The VHF uplink signal is up-converted to the UHF downlink signal linearly. The system has again of 150 dB with 60 dB of the total gain being adjustable. The communication system with transponder has a link margin of 10 dB.
Uplink center frequency
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145.965 MHz
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Downlink center frequency
|
435.225 MHz
|
Bandwidth
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±25 kHz
|
Output power
|
30 dBm (1W)
|
Receive sensitivity, gain
|
-120 dBm, 150 dB
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Total power consumption
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< 3 W
|
Automatic gain control
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Yes
|
Antennas
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Monopole (Cu-Be)
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PCB (Printed Circuit Board) size
|
8.8 cm x 8.8 cm x 0.5 cm
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Transponder mass
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< 250 g
|
Supply voltage
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2.8 V, 3.3 V, 5 V DC
|
Microcontroller
|
MSP430F5438
|
Specification of the transponder system
Illustration of the transponder desktop model (image credit: ITU)
Antenna system: The communication system consists of three subsystems with their backups: the modem, transponder, and the beacon.
System
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UHF Antenna (435 MHz)
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VHF Antenna (145 MHz)
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No of antennas
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Transponder
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2
|
2
|
4
|
Modem
|
2
|
2
|
4
|
Beacon
|
2
|
-
|
2
|
Total
|
6
|
4
|
10
|
Antenna system of the satellite communication subsystem
Source eoPortal
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