Amplifier design using a λ/4 high impedance bias line with a defected ground structure (DGS)

In this article, a new λ/4 bias line, combined with a dumbbell shaped defected ground structure (DGS), is proposed to suppress harmonics in power amplifiers. The proposed bias line maintains the required high impedance after the DGS is inserted, while the width and length of the λ/4 bias line are broader and shorter than those of conventional bias lines in power amplifiers. When the proposed bias line is used in power amplifiers, the third as well as the second harmonics are reduced because of the increased slow-wave effect of the proposed bias line over a wide harmonic frequency band. The proposed bias line is applied to a power amplifier for an IMT-2000 base station. It is shown that the reduction of the third harmonic component and the improvements in the 1 dB power compression point, power-added efficiency and IMD ₃ are 26.5 dB, 0.45 dB, 9.1 percent and 4.4 dB, respectively.