Compact Microstrip Branch-line Coupler with Wideband Harmonic Suppression

摘要

One compact microstrip branch-line coupler with wideband harmonic suppression is presented in this letter. The new structure has two significant advantages, which not only effectively reduces the occupied area to 26.5% of the conventional branch-line coupler at 0.96 GHz, but also has high 6th harmonic suppression performance. The measured results indicate that a bandwidth of more than 120 MHz has been achieved while the phase difference between S_(21) and S_(31) is within 90° ± 1°. The measured bandwidth of |S_(21)| and |S_(31)| within 3 ± 0.5 dB are 145 MHz and 150MHz, respectively. Furthermore, the measured insertion loss is comparable to that of a conventional branch-line coupler. The new coupler can be easily implemented by using the standard printed-circuit-board etching processes and is very useful for wireless communication systems.