Analysis and design of defected ground structure for EMC improvement in mixed‐signal transceiver modules

Abstract

In this research, the return path discontinuity (RPD), located under the power amplifier (PA) substrate, of X-band transceiver module (Base), mounted on a four-layer printed circuit board (PCB), is investigated to improve the signal integrity by reducing the difference in the reference potential. This study is performed by initially employing the wirebond method, through the assessment of both numbers and sizes of bondwires by advanced design system (ADS). Six bondwires of 25 µm are added, producing an improvement of 6.82 dB for the reflection coefficient and 1.19 dB for the isolation and insertion loss. For further improvement, spiral shape defected ground structure (DGS) is implemented in the inner ground layer (layer 2) without using bond wires. The DGS simulation results illustrate an improvement of 3 dB for S 11 and 0.6 dB for S 12. To improve the electromagnetic compatibility (EMC), the authors propose combination and integration of both wirebond and DGS methods, called wirebond-DGS method, which results in an improvement of 11.86 dB for S 11 , 1.34 dB for S 12 and S 21 , and 12.03 dB for S 22. Finally, the wirebond-DGS RF module was fabricated and the measurement results exhibit an improvement of 8.07 dB for S 11 and 9.39 dB for S 22 in comparison with the fabricated Base module. In addition, 0.53 dB improvement for both S 12 and S 21 is also achieved.