A K-band low-pass filtering power divider with two transmission zeros base on four-line interdigitated coupling structure

In this paper, a K-band low-pass filtering power divider (FPD) based on four-line interdigital coupling structure is proposed. There are four LC series resonators in parallel at the input and output ports, which can generate two transmission zeros at Ka band. The RLC is connected in series between two output ports to form an isolation network for better in-band isolation. The length of the transmission line can be reduced effectively by compensating the imaginary part of the input admittance. The two transmission lines have positive mutual inductance, making them less than 1/4 λ0 which helps to reduce the size of the devices. The EM simulation of the low-pass FPD designed in this paper shows that the 10-dB return-loss bandwidth is range from 13.42 to 28.14 GHz, the 10-dB isolation bandwidth is from 18.13 to 30.74 GHz. |S22| is smaller than -10 dB for 12.67-29.78 GHz, |S33| is smaller than -10 dB for 13.79-28.63 GHz. Each of the four identical coupling lines has a length of 0.058 λ0.The low-pass FPD occupies an area of $8.7 \times {10^{ - 3}}{\lambda _0}^2$.