PCB Embedded 2.4GHz Compact Bandpass Filter with Two Finite Transmission Zeros

In this paper, fully embedded 2.4 GHz WLAN band pass filter (BPF) is investigated into a multi-layered organic package substrate using high Q spiral stacked inductors and high Dk MIM capacitors for low cost RF system on package (SOP) applications. The proposed 2.4 GHz WLAN BPF is designed by modifying Chebyshev second order filter circuit topology. It is comprised of two parallel LC resonators for obtaining two transmission zeros. It is designed by using 2D circuit and 3D EM simulators for finding out optimal geometries and verifying their applicability. It exhibits an insertion loss of max -1.7dB and return loss of min -17dB. The two transmission zeros are observed at 1.85 and 6.7 GHz, respectively. In the low frequency band of 1.8 GHz - 1.9 GHz, the stop band suppression of min -23dB is achieved. In the high frequency band of 4.1 GHz - 5.4 GHz, the stop band suppression of min -18dB is obtained. It is the first embedded and the smallest one of the filters formed into the organic package substrate. It has a size of 2.2 x 1.8 x 0.77mm3.