Design of Dual-Band Bandpass Filters for Cognitive Radio Application of TVWS Band

• Published in: Journal of Electromagnetic Engineering and Science Vol. 16; no. 1; pp. 19 - 23
• Main Authors: Kwon, Kun-An, Kim, Hyun-Keun, Yun, Sang-Won
• Format: Journal Article
• Language: Korean
• Published: 2016
• Subjects: Cognitive Radio; Cross Coupling; Dual-Band BPF; TV White Space
• ISSN: 2671-7255; 2671-7263

This paper presents a novel design for dual-band bandpass filters. The proposed filters are applicable to the carrier aggregation of the TV white space (TVWS) band and long-term evolution (LTE) band for cognitive radio applications. The lower passband is the TVWS band (470-698 MHz) whose fractional bandwidth is 40 %, while the higher passband is the LTE band (824-894 MHz) with 8 % fractional bandwidth. Since the two passbands are located very close to each other, a transmission zero is inserted to enhance the rejection level between the two passbands. The TVWS band filter is designed using magnetic coupling to obtain a wide bandwidth, and the LTE band filter is designed using dielectric resonators to achieve good insertion loss characteristics. In addition, in the proposed design, a transmission zero is placed with cross-coupling. The proposed dual-band bandpass filter is designed as a two-port filter (one input/one output) as well as a three-port filter (one common input/two outputs). The measured performances show good agreement with the simulated performances.