Design of Stepped Impedance Microstrip Low-Pass Filter for Coexistence of TV Broadcasting and LTE Mobile System Close to 700 MHz

Abstract

The evolution of mobile networks has demanded more frequency spectrum and in many countries part of UHF band previously allocated to TV broadcasting now is used to broadband mobile networks and is important avoid any interference caused by signals transmitted in adjacent bands.

In the Brazil and in others countries the new spectrum is being assigned to Long Term Evolution (LTE) mobile networks at 700 MHz band that is close to the frequency spectrum used by TV broadcasting. In this context the paper presents a microstrip low-pass filter to be used into television and avoid interferences produced by LTE signals.

The proposed low-pass filter was designed using microstrip step-impedance method, fifth-order Chebyshev with ripple of 0.01 dB and cut-off frequency at 700 MHz. The designed low-pass filter was simulated using full wave simulator Ansoft HFSS. After simulation the low-pass filter was fabricated by photolithographic process in a FR-4 pcb. Finally, it was tested using vector network analyzer and the measured results presented a good agreement with the simulations.