Design and Realization of Organic LC Band Pass Filters

Band pass filters (BPF) using LC components, i.e. inductors and capacitors are widely used in radio frequency applications. These filters enable a band of frequencies to be passed through the filter, while those in the stop band of the band pass filter are rejected. In this study, a one-order chebyshev BPF with center frequency of 2.34GHz was designed in a four layer organic substrate with size of 1.5mm×0.86mm×0.25mm. The film type capacitor material was applied to fabricate the capacitor and the winding copper trace was applied to form the inductors. Based on the center frequency formula, the embedded capacitor value and inductor trace width were simulated and optimized by Ansoft HFSS. According to the model and the simulation results, the organic filters were fabricated at three different etching parameters to form three types of filters. Three typical filters with three different center frequencies of 1.6GHz, 1.9GHz, and 2.35GHz were tested, repectively. For the filter with center frequency of 2.35GHz meets the designed value of 2.34GHz. The maximum return loss is -26dB. The insertion loss is max. -1.07dB. In the lower frequency band of 1.0GHz-2.0GHz, the stop band suppression of -13.6dB to -18.1dB achieved. These results can meet the requirements of some low-end radio frequency device with frequency of 2.4GHz, so it is the potential technology to integrate the BPF in organic package substrate and PCB mother board for some specific application.