Highly miniaturized wideband 3‐dB branch‐line hybrid with second harmonic‐suppression

Abstract

AbstractIn this article, a highly miniaturized second harmonic suppressed 3‐dB branch‐line hybrid (BLH) with wideband performance is developed by employing a novel transmission‐line architecture (TLA). The proposed architecture consists of a coupled‐line, a series microstrip‐line and two open‐ended stubs. The even‐odd mode technique is used to formulate the required design equations. In order to reduce the size of the BLH, the internal areas between the branches are properly utilized for accommodating the proposed TLA structures with parameter values calculated using the derived formulas. To demonstrate this technique, a wideband three‐section BLH operating at 0.9 GHz is designed and fabricated. The measurement results show the proposed technique reduces the total circuit‐area of the BLH by 90.24% compared to the traditional three‐section hybrid while maintaining a fractional bandwidth greater than 53%. In addition, the second harmonic is eliminated utilizing the spurious response produced by the open‐ended stubs.