BDS RF Technology and Spectrum Management

Question 1

What is composite second order (CSO) distortion in a cable RF system?

Accepted Answer

Distortion products that fall at frequencies equal to the sum or difference of two carrier frequencies

Answer

CSO distortion products result from second-order nonlinearities in amplifiers, producing beats at frequencies equal to the sum and difference of pairs of channel carriers.

Question 2

What is the standard RF channel bandwidth for a US cable television channel?

Accepted Answer

6 MHz

Answer

US cable television channels are each 6 MHz wide, matching the legacy NTSC analog TV channel standard and carried forward for DOCSIS and QAM digital channels.

Question 3

Which modulation format offers the highest spectral efficiency for downstream cable broadband transmission?

Accepted Answer

QAM-1024

Answer

QAM-1024 encodes 10 bits per symbol, providing the highest spectral efficiency but requiring the highest CNR, and is supported in DOCSIS 3.1 OFDM channels.

Question 4

What is ingress noise in a cable return path system?

Accepted Answer

Unwanted signals from external sources that enter the coaxial plant through poor connectors or damaged cables

Answer

Ingress is RF energy from external sources (ham radio, AM broadcast, power lines) that enters the coaxial plant through shielding defects, degrading the upstream return path.

Question 5

What does MER (Modulation Error Ratio) measure in a digital cable system?

Accepted Answer

The ratio of the ideal QAM constellation point power to the error vector power, indicating signal quality

Answer

MER compares the power of the ideal QAM symbol to the power of the error vector (deviation from ideal), with higher MER indicating a cleaner, more accurately modulated signal.

BDS - Broadband Distribution Specialist Practice Test

BDS - Broadband Distribution Specialist Practice Test

BDS RF Technology and Spectrum Management