In this thesis we propose several novel configurations of bandpass filters (BPFs) with two transmission zeros by using the fractal theory. By means of the fractal theory, the dimension of the proposed BPFs can be effectively reduced. Furthermore, the proposed BPFs can be easily fabricated by using multilayer structure based on low-temperature cofired ceramic (LTCC) technology. Under the condition of the same dielectric thickness and coupling coefficient, we compared the conventional square open-loop BPF with the proposed fractal ones. The results show that the reduction in the dimension of the proposed BPFs is evident. Specifically, the dimension of the proposed Koch¡¦s, Minkowski_1st, and Minkowski_2nd filters can be reduced by about 36.5%, 32%, and 51.5%, respectively. Finally, the simulation and measurement results are reported in this thesis.

This thesis proposes methodology to design a balun with imaginary impedance. Under given specification, including center frequency, size, output impedance, our methodology can be used to evaluate its feasibility of implementation using high-DK LTCC(Low Temperature Cofired Ceramic) process. We then extend the design to incorporate a filter, which can simplify the circuit to reduce the required components. An example of our design operating at 2.4 GHz is implemented. Its size is 1600¡Ñ800¡Ñ650 um3, showing significant miniature. The simulation and measurement results are shown to verify the effectiveness of our design.

This thesis proposes an analytical method to synthesize bandpass filter with multiple transmission zeros. By using the six pre-determined parameters including two reflection zeros, two matching quality factors, and two transmission zeros, the method can exactly synthesize the corresponding prototype of second-order coupled-resonator bandpass filter. The synthesized filters not only can provide two pre-determined transmission zeros in the lower and upper side of the passband, but also can generate an extra transmission zero in the stopband. This thesis presents the prototypes of the bandpass filter and the methods of synthesis in detail. Finally this thesis implements compact LTCC bandpass filters by using the proposed synthesis method for 3.5 GHz WiMAX applications.