A compact fifth‐order bandpass filter (BPF) with high stopband rejection level is proposed using a coupled‐line‐stub cascaded structure (CLS‐CS). Based on transversal signal‐interference technique, the CLS‐CS is introduced to improve… Click to show full abstract
A compact fifth‐order bandpass filter (BPF) with high stopband rejection level is proposed using a coupled‐line‐stub cascaded structure (CLS‐CS). Based on transversal signal‐interference technique, the CLS‐CS is introduced to improve the characteristics of the filter, generating four new transmission zeros (TZs) close to band edge. The positions of all TZs are calculated through input impedance deduction. For demonstration, a BPF prototype centered at 2.1 GHz is designed with measured 3‐dB fractional bandwidth of 39% (1.68‐2.50 GHz) and stopband rejection levels of over 28.9 dB, which validates the proposed idea.
               
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