Compact Dual-band Branch-Line Coupler with Short-ended Stubs

Abstract

A novel compact dual-band branch line coupler with arbitrary power division is proposed. A conventional coupler loaded with half-wavelength short-ended stubs is adopted to realize the dual-band operations. Moreover, the frequency is tunable by changing the characteristic impedance of the transmission line. For practical verification, a branch line coupler ($\varepsilon_{\mathrm{r}}=2.65,\ h=0.5 \text{mm}$) operation at 0.9/1.8GHz is constructed in microstrip technology and tested. The measured results are in good agreement with the simulated ones.