Substrate Integrated Waveguide Frequency Reconflgurable Filter Controlled by Magnetic Field

In this work, a novel upper and lower sideband tunable SIW bandpass ferrite fllter is presented. With the application of an external magnetic bias on the ferrite slabs, the lower sideband of the fllter can be adjusted from 8.8GHz to 10.7GHz and the upper sideband can be tuned from 9.3GHz to 12.0GHz. Compared to previously reported frequency tunable SIW fllters, the proposed fllter ofiers a relatively wide tuning range and ∞exibly reconflgurable abilities while dramatically reducing the complexity of external control circuit. Frequency tunable/reconflgurable fllters have special signiflcance in future smart and miniaturized wireless systems (1,2). The currently popular substrate integrated waveguide (SIW) technique (3) combines the best and complementary features of both planar transmission lines and non-planar waveguides. Thus it is found very appropriate in microwave and millimeter-wave tunable fllter applications. Researchers try to realize some SIW reconflgurable fllters by use of PIN diodes (4,5) and varactors (6,7). Unlike those conventional planar transmission lines, such as the microstrip line, the SIW is a uniconductor guided-wave structure and has the same electric potential for each metallic surface. Therefore, some di-culties exist in electronically tunable SIW designs. Besides, complex DC bias circuits may lead to unwanted leakage and interference. Tuning operation characteristics of SIW components by magnetic fleld is another possible way of avoiding these problems. In this paper, a tunable bandpass fllter is designed with YIG ferrite employed in. Both lower sideband and upper sideband of the fllter can be adjusted separately. This ferrite-loaded SIW fllter can be considered as two sub-components. Design principles of these two sub-components are based on isolator and switch respectively. Up to now most reconflgurable SIW bandpass fllters are achieved by resonant cavity (8{11). In (12) circulators/isolators are used as tunable bandpass fllter. However no publication is found to use isolator and switch to achieve reconflgurable bandpass fllter. 2. FILTER IMPLEMENTATION This ferrite bandpass fllter is proposed of a reconflgurable highpass fllter, which is based upon ferrite switches, and a tunable broadband isolator can be viewed as a bandstop fllter. In this section, these two sub-components are designed respectively. At last, the SIW frequency reconflgurable fllter is proposed. The substrate used is 0.508mm thick Rogers6010 substrate. Its permittivity and loss tangent are 10.2 and 0.0023, respectively. YIG ferrite is employed in this design. Its saturation magnetization value is 1850Gs, relative dielectric constant is 14.5, and 3dB line width is 20Oe. All ferrite slabs used in this design is as thick as the substrate.