New dual-mode microstrip bandpass Filter with a Square Notch

A new planar dual-mode microstrip bandpass filter with a square notch is proposed. The proposed filter structure uses a single patch without coupling gaps. This filter has two transmission zeros on both sides of the passband. The insertion loss is <; 1dB and return loss is >; 10dB within 1.96-2.13GHz, and the minimum insertion loss is 0.07dB at about 2.05GHz. The 3dB fractional bandwidth is 12.73%. The effect on the filter´s performance by changing filter parameters is studied. The results show that this new filter can provide a low insertion loss and reduce uncertainty in fabrication. It also makes miniaturization easy.