Ultra-Wideband Bandpass Filter Using Solder-Mask-Based Multilayer Technology

This paper presents the design of an Ultra-Wideband (UWB) quasi-lumped elements bandpass filter on multilayer Printed Circuit Board (PCB) technology. The originality of this work relies in the use of a multilayer stack. This technology is based on a PCB with one or several additional layers of solder-mask, used as a dielectric layer in this case. Introduction of solder-mask overcomes some conventional planar limitations like the range of characteristic impedances and couplings. The goal is to improve performances of planar quasi-lumped elements topology such as bandwidth and out-of-band rejection while retaining standard fabrication methods and materials. The advantages of the proposed method are illustrated on two demonstrators by simulations and experimental results. The measured filters exhibit a wide bandwidth with a strong out-of-band rejection in comparison with an UWB filter manufactured through a classical planar technology. The first filter is designed and optimized to operate from 2.6GHz to 11.5GHz with a high rejection level of 38dB, the second filer is designed and optimized to operate from 1.7GHz to 11GHz with a rejection level of 20dB.