Ultra-Wideband Bandpass Low-Cost Multilayer Technologies Filter Using Varnish

In this paper, a new method for ultra-wide band (UWB) bandpass filter design is proposed. This new filter is fabricated using varnish to obtain a multilayer technology, which achieves complex filter structures meeting very hard electrical specifications. Moreover, it has a lower production cost compared to classical multilayer technologies like Low Temperature Co-Fired Ceramic (LTCC) and Organic Substrate Technologies (OST). In first, our objective is to improve the wide band performances and rejection with this new technology. In particular, the coupling between the resonators is increased by superposing resonators or floating metallic patches using varnish. The benefits of the proposed method are also illustrated with simulations and experimental results. The fabricated varnish filter reaches an ultra-wide fractional bandwidth of 100 % and a good level of rejection out of the bandwidth. These proposed filters can be used in communication and radar systems.