Abstract

In this paper, a new defected ground structure (DGS) λ /4 bias line that dumbbell-shaped ground pattern is etched on ground plane of microstrip line is proposed. This DGS λ /4 bias line maintains high impedance, but physical width is wider and length is shorter than that of the conventional bias line. If the proposed bias line is attached on signal transmission line, this bias line can reduces the 3 rd harmonic signal as well as the 2 nd harmonic signal. With harmonic reduction characteristics, efficiency and linearity of amplifier are improved. When the proposed bias line is adopted in power amplifier on IMT-2000 basestation transmitting band, the 3 rd harmonic signal is reduced about 26.5dB and efficiency is improved about 9.1% and IMD3 is improved 4.5dB than the conventional structure.