What is meant by “direct sampling” in software defined radios?
The correct answer is C: Incoming RF is digitized by an analog-to-digital converter without being mixed with a local oscillator signal. What is meant by 'direct sampling' in software defined radios is that incoming RF is digitized by an analog-to-digital converter without being mixed with a local oscillator signal. Direct sampling digitizes RF directly. For amateur radio operators, this is important for SDR technology. Understanding this helps when working with SDRs.
Exam Tip
Direct sampling in SDR = incoming RF digitized by ADC without being mixed with LO signal. Think 'D'irect 'S'ampling = 'D'irectly 'S'amples RF (no mixing). Direct sampling digitizes RF directly. Not software conversion, not I/Q generation, not switching mixer - just direct RF digitization.
Memory Aid
"Direct sampling in SDR = incoming RF digitized by ADC without being mixed with LO signal. Think 'D'irect 'S'ampling = 'D'irect RF digitization. Direct sampling digitizes RF directly. Important for SDR technology."
Real-World Application
Direct sampling in software defined radios: It means incoming RF is digitized by an analog-to-digital converter without being mixed with a local oscillator signal. The RF is sampled directly at the antenna. This is what direct sampling means - direct RF digitization.
Key Concepts
Why Other Options Are Wrong
Option A: Incorrect. Software converted from source to object code during operation isn't direct sampling - direct sampling digitizes RF directly. Software conversion isn't direct sampling.
Option B: Incorrect. I and Q signals generated by digital processing without RF amplification isn't direct sampling - direct sampling digitizes RF directly. I/Q generation isn't direct sampling.
Option D: Incorrect. Switching mixer generating I and Q directly isn't direct sampling - direct sampling digitizes RF directly without mixing. Switching mixer isn't direct sampling.
题目解析
The correct answer is C: Incoming RF is digitized by an analog-to-digital converter without being mixed with a local oscillator signal. What is meant by 'direct sampling' in software defined radios is that incoming RF is digitized by an analog-to-digital converter without being mixed with a local oscillator signal. Direct sampling digitizes RF directly. For amateur radio operators, this is important for SDR technology. Understanding this helps when working with SDRs.
考试技巧
Direct sampling in SDR = incoming RF digitized by ADC without being mixed with LO signal. Think 'D'irect 'S'ampling = 'D'irectly 'S'amples RF (no mixing). Direct sampling digitizes RF directly. Not software conversion, not I/Q generation, not switching mixer - just direct RF digitization.
记忆口诀
Direct sampling in SDR = incoming RF digitized by ADC without being mixed with LO signal. Think 'D'irect 'S'ampling = 'D'irect RF digitization. Direct sampling digitizes RF directly. Important for SDR technology.
实际应用示例
Direct sampling in software defined radios: It means incoming RF is digitized by an analog-to-digital converter without being mixed with a local oscillator signal. The RF is sampled directly at the antenna. This is what direct sampling means - direct RF digitization.
错误选项分析
Option A: Incorrect. Software converted from source to object code during operation isn't direct sampling - direct sampling digitizes RF directly. Software conversion isn't direct sampling. Option B: Incorrect. I and Q signals generated by digital processing without RF amplification isn't direct sampling - direct sampling digitizes RF directly. I/Q generation isn't direct sampling. Option D: Incorrect. Switching mixer generating I and Q directly isn't direct sampling - direct sampling digitizes RF directly without mixing. Switching mixer isn't direct sampling.
知识点
Direct sampling, Software defined radios, Incoming RF digitized, Analog-to-digital converter, Without being mixed with local oscillator signal
Verified Content
Question from official FCC Extra Class question pool. Explanation reviewed by licensed amateur radio operators.