The relationship between low-frequency dispersion and the intermodulation performance of AlGaAs/GaAs HBTs has been demonstrated for thc first time. The theoretical analysis and experimenf a1 results indicate that IM3 wil I depend strongly on the frequency spacing (Af = j 2 -f i ) in the two-tone measurement.

A novel fractal structure using Koch and Sierpinski fractalshapes is proposed. By inserting the Sierpinski carpets into the single patch and etching the inner and outer patch edges according to Koch curves, the resonant frequency of the patch antenna can be lowered significantly. And the higher of the iteration order of the fractal shapes, the lower the resonant frequency becomes. In this paper, a novel smallsize single patch microstrip antenna based on the proposed fractalshapes is designed, fabricated and measured. It is experimentally found that the size reduction can reach 80.3%. Compared to the conventional square single patch antenna, the proposed antenna maintains comparable radiation patterns. Therefore, the small-size single patch microstrip antenna considered here can be applied to portable wireless communication systems requiring small devices.

In this paper, on the basis of proposing a novel complementary split-ring resonator (CSRR) using Koch fractal curve, a bandpass filter based on such a new structure is designed To validate the designing method. Transmission characteristics and reflection characteristics of the presented filter are given by both software simulation and experiment measurement. Consistent results have confirmed the design concept and excellent performance of the new structure and indicated that the proposed filter has a low insertion loss a high selectivity and small size.

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