A 60GHz 3-dB tandem coupler using offset broadside-coupled lines on a silicon substrate

Abstract

In this letter, a 60GHz tandem coupler using offset broadside-coupled lines is proposed on a silicon-based integrated passive device technology. Over the frequency band of 57-66GHz, the measured insertion loss, amplitude imbalance, input return loss, isolation and phase error of the designed tandem coupler are better than 0.67dB, 0.31dB, 27.9dB, 29.7dB and 3.7° respectively. To the best of our knowledge the proposed coupler achieves the lowest reported insertion loss and amplitude imbalance for a 3-dB coupler on a silicon substrate at 60GHz band. Furthermore using the even- and odd-mode analysis, the reason for a high directivity of edge-coupled lines and a low coupling level of broadside-coupled lines on the adopted technology is investigated and a solution for increasing the coupling level of broadside-coupled lines is proposed.