Modulation families: ASK, PSK, FSK, and QAM are examples of which encoding category where digital data modulates an analog carrier?

Introduction / Context: To send binary information over band-limited analog channels (like radio or passband links), we modulate a sinusoidal carrier. The family names ASK, PSK, FSK, and QAM refer to how the carrier’s properties are altered in response to digital symbols. Identifying the correct encoding class reinforces the separation between line coding and passband modulation.

Given Data / Assumptions:

• ASK = Amplitude Shift Keying; PSK = Phase Shift Keying; FSK = Frequency Shift Keying; QAM = Quadrature Amplitude Modulation.
• Input: digital information (bits/symbols).
• Output: an analog passband waveform suitable for channels that carry sine-like signals.

Concept / Approach: In digital-to-analog encoding, a digital symbol stream changes analog carrier parameters (amplitude, frequency, phase, or combinations). That distinguishes it from digital-to-digital line codes (e.g., NRZ, Manchester), analog-to-analog modulation (AM/FM for analog sources), and analog-to-digital conversion (sampling/quantization like PCM). Thus ASK/PSK/FSK/QAM are clearly digital-to-analog methods.

Step-by-Step Solution:

Verification / Alternative check: Examples include modem standards where bitstreams are conveyed via PSK/QAM over telephone lines and radio links, confirming the digital-to-analog classification.

Why Other Options Are Wrong:

Common Pitfalls: Mixing up line coding with modulation; forgetting that “keying” implies digital symbol control of a continuous carrier.

Final Answer: digital-to-analog.