Balanced filter with wide stopband using asymmetrical coupled lines

A novel wideband balanced filter with wide stopband using asymmetrical coupled lines and stubs are proposed in this paper. Wide passband for the differential mode and wideband common mode suppression can be realized due to the asymmetric circuits. Stepped coupled lines are used to replace the coupled lines to extend the upper stopband. A planar wideband balanced filter with 3-dB bandwidth over 80% is designed for the 4-Genertion Long-Term-Evolution bands. The upper stopband for the balanced filter can be extended up to four octaves.