STK Communications, together with the Chain and Constellation objects, makes it easy to model analog and digital transponders.
Click here for a step-by-step walkthrough on the modeling of analog and digital transponders.
How to Model an Analog Transponder
In an analog transponder, the transmitted signal is essentially a reflection of the received signal, with the added possibility of frequency translation or power amplification:
STK Communications models an analog transponder as a combination of a receiver and a retransmitter. To model a link that includes an analog transponder, set up a chain with links to the receiver and from the retransmitter. For example, to model a simple one-hop link from a ground transmitter to a ground receiver via an analog satellite transponder, define a chain with the following constituent links:
- ground transmitter to satellite receiver (uplink)
- satellite receiver to satellite retransmitter (downlink)
- satellite retransmitter to ground receiver
If you select the chain in the object browser and generate a Bent Pipe Comm Link report, you will see that link performance degrades in the downlink and further in the composite link.
How to Model a Digital Transponder
In a digital (or regenerative) transponder, there is complete demodulation and re-modulation of the incoming signal before it is sent:
STK Communications models a digital transponder as a combination of a receiver and a transmitter. To model a link that includes a digital transponder, set up a chain with links to the receiver and from the transmitter. For example, to model a simple one-hop link from a ground transmitter to a ground receiver via a digital satellite transponder, define a chain with the following constituent links:
- ground transmitter to satellite receiver (uplink)
- satellite receiver to satellite transmitter (downlink)
If you select the chain in the object browser and generate a Bent Pipe Comm Link report, you will see that link performance may degrade in the downlink but no further degradation occurs in the composite link.