Influences of defected ground structure on different ground planes in RF power amplifier

This paper presents the effects of defected ground structure (DGS) on different ground planes in RF power amplifiers (PAs). Two DGS patterns etched on the front and back planes of printed circuit board which are named Top-DGS and Bottom-DGS, and a thru microstrip line are manufactured and measured to compare the insert loss at the fundamental and second harmonic frequencies. In order to evaluate the effects of the Top-DGS, Bottom-DGS and without DGS on the PA, three 4 W PA have been designed and measured. Measured results show that the PA with the Top-DGS can reject the second harmonic about 13 dB at Pout 34.76 dBm, and achieve better the output power (Pout) and power added efficiency (PAE) than the one without DGS; the one with the Bottom-DGS has the suppression of about 28dB for the second harmonic at Pout 34.21 dBm, and has less the Pout and PAE for the decreased characteristic impedance (Z₀) of DGS pattern.