Question
What is the purpose of the series capacitor in a gamma match?
Answer Options
- A) To provide DC isolation between the feed line and the antenna
- B) To cancel unwanted inductive reactance
- C) To provide a rejection notch that prevents the radiation of harmonics
- D) To transform the antenna impedance to a higher value
Correct Answer: B
Explanation
The Gamma match uses a matching rod placed parallel to the driven element and connects the feed line conductor via a series capacitor. This mechanical structure, combined with the slight lengthening of the driven element needed for the match, introduces a degree of unwanted inductance into the feed system.
To ensure a purely resistive match, this unwanted inductance must be cancelled. The purpose of the series capacitor in a gamma match is to cancel unwanted inductive reactance. The capacitor’s value is chosen to resonate the overall structure back to a purely resistive impedance at the operating frequency, providing a clean 50Ω match.
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