What is the phase difference between the I and Q RF signals that software-defined radio (SDR) equipment uses for modulation and demodulation?
The correct answer is B: 90 degrees. The phase difference between the I and Q RF signals that software-defined radio (SDR) equipment uses for modulation and demodulation is 90 degrees. I (In-phase) and Q (Quadrature) signals are 90° apart, allowing complete signal representation. For amateur radio operators, this is fundamental SDR operation. Understanding this helps when using SDR equipment.
Exam Tip
I and Q phase difference = 90 degrees. Think 'I' and 'Q' = 'I'n-phase and 'Q'uadrature = '9'0 degrees apart. I and Q signals are 90° apart, allowing complete signal representation. Not zero, not 180°, not 45° - just 90°.
Memory Aid
"I and Q phase difference = 90 degrees. Think 'I' and 'Q' = '9'0 degrees apart. I and Q signals are 90° apart, allowing complete signal representation. Fundamental SDR operation requirement."
Real-World Application
SDR equipment uses I (In-phase) and Q (Quadrature) signals for modulation and demodulation. The I and Q signals are 90 degrees apart in phase. This quadrature relationship allows the SDR to represent any signal (amplitude and phase) using just I and Q. 90 degrees is the required phase difference.
Key Concepts
Why Other Options Are Wrong
Option A (Zero): Incorrect. Zero degrees would mean I and Q are in phase - they need to be 90° apart for quadrature operation. Zero degrees doesn't work.
Option C (180 degrees): Incorrect. 180 degrees would mean I and Q are opposite phase - they need to be 90° apart for quadrature operation. 180 degrees doesn't work.
Option D (45 degrees): Incorrect. 45 degrees is too small - I and Q need to be 90° apart for quadrature operation. 45 degrees doesn't work.
题目解析
The correct answer is B: 90 degrees. The phase difference between the I and Q RF signals that software-defined radio (SDR) equipment uses for modulation and demodulation is 90 degrees. I (In-phase) and Q (Quadrature) signals are 90° apart, allowing complete signal representation. For amateur radio operators, this is fundamental SDR operation. Understanding this helps when using SDR equipment.
考试技巧
I and Q phase difference = 90 degrees. Think 'I' and 'Q' = 'I'n-phase and 'Q'uadrature = '9'0 degrees apart. I and Q signals are 90° apart, allowing complete signal representation. Not zero, not 180°, not 45° - just 90°.
记忆口诀
I and Q phase difference = 90 degrees. Think 'I' and 'Q' = '9'0 degrees apart. I and Q signals are 90° apart, allowing complete signal representation. Fundamental SDR operation requirement.
实际应用示例
SDR equipment uses I (In-phase) and Q (Quadrature) signals for modulation and demodulation. The I and Q signals are 90 degrees apart in phase. This quadrature relationship allows the SDR to represent any signal (amplitude and phase) using just I and Q. 90 degrees is the required phase difference.
错误选项分析
Option A (Zero): Incorrect. Zero degrees would mean I and Q are in phase - they need to be 90° apart for quadrature operation. Zero degrees doesn't work. Option C (180 degrees): Incorrect. 180 degrees would mean I and Q are opposite phase - they need to be 90° apart for quadrature operation. 180 degrees doesn't work. Option D (45 degrees): Incorrect. 45 degrees is too small - I and Q need to be 90° apart for quadrature operation. 45 degrees doesn't work.
知识点
I and Q signals, 90 degrees, Phase difference, SDR
Verified Content
Question from official FCC General Class question pool. Explanation reviewed by licensed amateur radio operators.