Wideband multi-section quadrupled inductive-compensated parallel-coupled lines

A high directivity wideband planar coupler based on multi-section inductive-compensated parallel- coupled lines is proposed. The technique is simply achieved by connecting the optimum inductors at all coupler´s ports of parallel-coupled lines. The inductors function as directivity compensating elements. Also, the proposed coupler is excellently matched at all ports. The technique is verified by the experimental results of 10-dB three-section microstrip couplers. Comparison of the performances of the proposed technique with the uncompensated and two previously inductive-compensated techniques are discussed. Good results of the coupling bandwidth, return loss, and the directivity are obtained from the proposed multi-section coupled lines.