What is the purpose of using multiple driven elements connected through phasing lines?
The correct answer is A: To control the antenna's radiation pattern. The purpose of using multiple driven elements connected through phasing lines is to control the antenna's radiation pattern. By adjusting the phase relationships between elements, you can steer and shape the radiation pattern.
Multiple driven elements with phasing lines allow you to control the phase of each element relative to the others. By adjusting the phase (through different phasing line lengths or phase shifters), you can steer the main lobe in different directions, create nulls in specific directions, or shape the overall pattern. This is how phased arrays work - multiple elements with controlled phase relationships create steerable, directional patterns. Phasing lines are transmission lines of specific lengths that create the desired phase shifts between elements.
Exam Tip
Multiple driven elements + phasing = Pattern control. Remember: Multiple driven elements connected through phasing lines are used to control the antenna's radiation pattern - steering lobes, creating nulls, and shaping the pattern.
Memory Aid
"**M**ultiple **D**riven + **P**hasing = **P**attern **C**ontrol (think 'MD+P = PC')"
Real-World Application
You build a two-element array with phasing lines. By adjusting the phasing line lengths, you can steer the main lobe - maybe 30 degrees to the left or right. You can also create nulls in specific directions to reject interference. The phasing lines control the phase relationships, which control the radiation pattern.
FCC Part 97.3Key Concepts
Why Other Options Are Wrong
Option B: Incorrect. Phasing lines don't prevent harmonic radiation. Harmonic suppression requires filters, not phasing.
Option C: Incorrect. Phasing lines don't allow single-band antennas to operate on other bands. They control pattern, not frequency response.
Option D: Incorrect. While phasing can affect elevation pattern, the primary purpose is overall radiation pattern control (direction, nulls, lobes), not specifically creating low-angle patterns.
题目解析
The correct answer is A: To control the antenna's radiation pattern. The purpose of using multiple driven elements connected through phasing lines is to control the antenna's radiation pattern. By adjusting the phase relationships between elements, you can steer and shape the radiation pattern. Multiple driven elements with phasing lines allow you to control the phase of each element relative to the others. By adjusting the phase (through different phasing line lengths or phase shifters), you can steer the main lobe in different directions, create nulls in specific directions, or shape the overall pattern. This is how phased arrays work - multiple elements with controlled phase relationships create steerable, directional patterns. Phasing lines are transmission lines of specific lengths that create the desired phase shifts between elements.
考试技巧
Multiple driven elements + phasing = Pattern control. Remember: Multiple driven elements connected through phasing lines are used to control the antenna's radiation pattern - steering lobes, creating nulls, and shaping the pattern.
记忆口诀
**M**ultiple **D**riven + **P**hasing = **P**attern **C**ontrol (think 'MD+P = PC')
实际应用示例
You build a two-element array with phasing lines. By adjusting the phasing line lengths, you can steer the main lobe - maybe 30 degrees to the left or right. You can also create nulls in specific directions to reject interference. The phasing lines control the phase relationships, which control the radiation pattern.
错误选项分析
Option B: Incorrect. Phasing lines don't prevent harmonic radiation. Harmonic suppression requires filters, not phasing. Option C: Incorrect. Phasing lines don't allow single-band antennas to operate on other bands. They control pattern, not frequency response. Option D: Incorrect. While phasing can affect elevation pattern, the primary purpose is overall radiation pattern control (direction, nulls, lobes), not specifically creating low-angle patterns.
知识点
Multiple driven elements, Phasing lines, Radiation pattern control, Phased array
Verified Content
Question from official FCC Extra Class question pool. Explanation reviewed by licensed amateur radio operators.