Meaning of “4/6 GHz” band plan in satellite links When a satellite system is described as operating at “4/6 GHz,” what do these paired frequencies indicate?
-
A4 GHz is the uplink and 6 GHz is the downlink frequency
-
B4 GHz is the downlink and 6 GHz is the uplink frequency
-
CThe system operates at a single mean frequency of 5 GHz
-
DOne frequency is a back-up for the other
-
EThey refer to beacon frequencies only
Answer
Correct Answer: 4 GHz is the downlink and 6 GHz is the uplink frequency
Explanation
Introduction / Context:Band-pair notation is standard in satellite communications. In C-band systems, “6/4 GHz” or “4/6 GHz” quickly conveys the uplink and downlink allocations. Understanding this shorthand is essential for link budgeting and regulatory coordination.
Given Data / Assumptions:
- C-band fixed-satellite service typically uses ~5.925–6.425 GHz (uplink) and ~3.7–4.2 GHz (downlink).
- Paired bands are separated to ensure adequate isolation between transmit and receive chains.
Concept / Approach:
In common practice, the higher frequency is used for Earth-to-space (uplink) and the lower frequency is used for space-to-Earth (downlink), primarily due to path loss and rain attenuation considerations and to simplify onboard filtering/isolation.
Step-by-Step Solution:
Identify standard C-band pair: uplink ≈ 6 GHz, downlink ≈ 4 GHz.Map the notation “4/6 GHz” to downlink/uplink respectively.Select the option reflecting 4 GHz (down) and 6 GHz (up).Verification / Alternative check:
ITU tables and operator band plans confirm the 6 GHz uplink and 4 GHz downlink convention for C-band FSS.
Why Other Options Are Wrong:
Reversing the pair contradicts standard allocations; a “mean frequency” is not used; backup interpretation is incorrect.
Common Pitfalls:
Confusing Ku-band and Ka-band pairs; always check whether the convention lists down/up or up/down, but C-band pairing is well-established.
Final Answer:
4 GHz is the downlink and 6 GHz is the uplink frequency