The Research Of Miniaturized High-performance Filters Based On Metamaterials

As engineered artificial materials, electromagnetic metamaterials thatexhibitsunusual properties which are not available in natural materials. Recent researchanddevelopment have shown promising optical and microwave applications ofmetamaterials. With the ability to manipulate electromagnetic waves propagatingthrough its medium, electromagnetic metamaterials are believed to hold an importantkey to many future optical and microwave devices and systems. As one of the necessarypassive elements in wireless communication and Radar systems, miniaturized andhighly integrated filters are believed as the key part in the design of modern microwaveand millimeter-wave systems. This dissertation aims at the high-performanceminiaturized metamaterials filters utilizing the conventional or improved unit cell ofmetamaterials. The major contributions are listed as following:Firstly, the basic principles and the theories of CRLH-type and resonantmetamaterials are introduced. The equivalent circuits of ordinary CRLH TL areextracted, and the advantages of balanced CRLH circuits are analyzed. What is more,different kinds of SRR-type resonance are specifically discussed and the uniqueproperties of various SRR-type resonances are summarized.Then, on the basis of conventional cell of CRLH transmission line, aultra-wide-band filter is realized. In addition, one cell high-quality CRLH filter andtwo-cell cascaded narrow-band CRLH filters are proposed. By introducing microstripstubs and magnetic coupling to the common CRLH unit cell, the out-of-band selectivityis improved obviously without scaling up the filter size. The equivalent circuits of themicrostrip stubs and the magnetic coupling are extracted, which makes convenient forthe fast and accurate modeling and simulation. The odd-even mode networks are alsoapplied to the novel filters, which theoretically justified the way of design is effective.At last, on the basis of SRR loaded to the conventional transmission line,short-end-TL and open-end-TL filters are proposed, which makes the properties of thepass bands optimized. Besides, the SRRs are introduced to the classical cross coupledfilters, which creates four transmission zeros in the rejection band. By introducing and strengthening the coupling effects between the host transmission line ends and the splitring resonances, the properties of the filters improved obviously. What’s more, thisstructure is convenient for the implemtentation of dual-band filters. Meanwhile theintroduction of cross coupling and0°feed structure guarantees the good out-of-bandperformance of the SRR-type filter.