Compact Wideband Four-coupled-line Based Filtering Directional Coupler with Wide Upper Stopband

Le résumé fourni par la source

A compact wideband filtering directional coupler (FDC) with wide upper stopband is proposed, which consists of a coupler based on unequal-width four-coupled-lines (FCL) and four filtering sections. The filtering section is composed of coupled lines load with open-circuited stubs. The FCL-based coupler has the inherent filtering performance with two transmission zeros. On the basis, the wide upper stopband with more than 20-dB suppression is obtained by connecting four filtering sections to the ports of the coupler. Theoretical analysis is performed and optimization procedures are given. For demonstration, a prototype operating at 2GHz is designed, fabricated and measured. The measurement results show that within the fractional bandwidth of more than 50%, the coupler exhibits more than 10dB return loss, larger than 10dB isolation, less than 0.5dB amplitude imbalance and the phase difference error is within 5°. Besides, the rectangle coefficient of 1.41 is achieved with the 20-dB stopband rejection reaching 4.47f0. The dimension of the fabricated FDC is 0.32λg× 0.17λg, which is the smallest one among FDCs with wide upper stopband. Due to that the proposed coupler has the merits of planar structure, miniaturized size, wide filtering bandwidth, good frequency selectivity, and large upper stopband, it has a potential application in high-integrated wireless communication systems.

Ce résumé expose les affirmations des auteurs. BNTIC ne l’interprète pas comme une validation indépendante des résultats.