A.1/2波長(zhǎng)的整數(shù)倍 B.1/4波長(zhǎng)的奇數(shù)倍 C.1/4波長(zhǎng)的整數(shù)倍 D.1/2波長(zhǎng)的奇數(shù)倍
A.3dB B.6dB C.9dB D.12dB