BDS Signal Distribution and Amplification 1 — Questions and Answers
Question 1: What is the primary purpose of a distribution amplifier in a cable broadband system?
- To convert analog signals to digital
- To compensate for signal loss in the coaxial cable plant (Correct answer)
- To encrypt subscriber traffic
- To route IP packets between nodes
Correct answer: To compensate for signal loss in the coaxial cable plant
Distribution amplifiers boost signal levels to overcome the attenuation caused by coaxial cable and passive splitters in the distribution network.
Question 2: Which parameter describes the ratio of desired signal power to noise power in a cable distribution system?
- MER
- SNR
- BER
- CNR (Correct answer)
Correct answer: CNR
Carrier-to-Noise Ratio (CNR) measures the ratio of the carrier signal power to the noise floor, which is a key quality metric in cable RF systems.
Question 3: A BDS technician measures a -6 dBmV signal level at a tap port. After a 3.5 dB tap value, what is the signal level on the output side of the tap?
- -2.5 dBmV
- -9.5 dBmV (Correct answer)
- -6 dBmV
- -12 dBmV
Correct answer: -9.5 dBmV
The tap value represents insertion loss, so the output level equals the input level minus the tap value: -6 dBmV - 3.5 dB = -9.5 dBmV.
Question 4: What is the typical downstream frequency range used by DOCSIS 3.1 systems in the US cable plant?
- 5–42 MHz
- 54–1002 MHz (Correct answer)
- 108–750 MHz
- 5–85 MHz
Correct answer: 54–1002 MHz
DOCSIS 3.1 utilizes the downstream spectrum from 54 MHz up to 1002 MHz (1 GHz) in the extended spectrum plant.
Question 5: Which type of amplifier is typically used at the output of a cable headend to drive the trunk coaxial cable?
- Line extender amplifier
- Bridger amplifier
- Trunk amplifier (Correct answer)
- Distribution amplifier
Correct answer: Trunk amplifier
Trunk amplifiers are high-gain, low-noise amplifiers designed to drive long trunk cable segments originating from the headend.
Question 6: What effect does cascading multiple amplifiers have on the noise figure of a cable distribution system?
- Noise figure improves with each additional amplifier
- Noise figure remains constant regardless of cascade depth
- Noise figure degrades as more amplifiers are added in cascade (Correct answer)
- Noise figure is only affected by the last amplifier in the chain
Correct answer: Noise figure degrades as more amplifiers are added in cascade
Each amplifier in cascade adds its own noise contribution, causing the cumulative noise figure to degrade as cascade depth increases.
BDS Signal Distribution and Amplification 1
What is the primary purpose of a distribution amplifier in a cable broadband system?