Design techniques for dual-passband filters

• Published in: IEEE transactions on microwave theory and techniques 2005-11, Vol.53 (11), p.3265-3271
• Main Authors: Macchiarella, G., Tamiazzo, S.
• Format: Article
• Language: English
• Subjects: Applied sciences; Band pass filters; Chebyshev filters; Circuit properties; circuit synthesis; Communication systems; Design engineering; Design methodology; Electric, optical and optoelectronic circuits; Electronic circuits; Electronics; elliptic filters; Equipments and installations; Exact sciences and technology; Filtering theory; Frequency filters; Frequency synthesizers; GSM; Holes; Microwave circuits, microwave integrated circuits, microwave transmission lines, submillimeter wave circuits; Microwave filters; Microwaves; Mobile radiocommunication systems; Passband; Placing; Prototypes; Radiocommunications; Rejection; Synthesis; System testing; Telecommunications; Telecommunications and information theory; Theoretical study. Circuits analysis and design; Topology; Transformations
• ISSN: 0018-9480; 1557-9670
• DOI: 10.1109/TMTT.2005.855749

This paper introduces two possible approaches to the design of microwave filters presenting two passbands separated by one rejection band, which is created by suitably placing transmission zeros in the stopband. In the first method, the two passbands have almost equal extension and the transmission zeros are symmetrically placed in the stopband; the second method instead allows the synthesis of filters with different passbands width and all the transmission zeros in the stopband placed at the same frequency. Both design methods are based on suitably defined frequency transformations and employ well-established prototype synthesis techniques; the practical implementation is performed through the classical multiple-coupled cavity topology. Two test filters operating in the global system for mobile communication 800-MHz band, designed with the described procedures and actually fabricated, have validated the novel design methods.