Fully embedded UWB filter into organic packaging substrate

In this paper, a compact ultra wideband bandpass filter has been newly designed and implemented by embedding all the passive components into an organic packaging substrate for compact 3.1 - 4.75 GHz UWB system applications. In order to reduce a size of the filter and avoid unwanted EM coupling among the embedded filter circuit elements, it was designed by using a modified 3rd cehbyshev circuit topology and J-inverter transformation technology. It was comprised of three shunt-type LC resonators, two capacitance J-inverters, two extra transmission zero inductors, and one extra transmission zero capacitor. The capacitor and inductors generate finite transmission zeros to enhance rejection characteristics at independent proper sides. The measured maximum insertion loss in the passband ranged from 3.1 to 4.75 GHz was better than 1.68 dB, with a minimum value of 0.78 dB at 3.75 GHz. And the return loss was higher than 12 dB in the passband. The transmission zeros of the measured response occurred at 2.2, and 5.15 GHz, and provided suppressions of 31 dB at 2.4 GHz(ISM band) and 20 dB at 5.15 GHz(wireless LAN band), respectively. Group delay was lower than 0.62 ns in the passbnad. The size of the designed bandpass filter was 2.9 mm times 2.8 mm times 0.55 mm which was much smaller than the ones fabricated onto organic substrate.