| dc.description.abstract | In this study, two kinds of multi-functional bandpass filter based on multicoupled line are proposed, which are the balun bandpass filter and the bandpass power divider. They are achieved by the proper placements of ground terminations and loaded capacitors of a multicoupled line. The effective length of the multicoupled line can be shorter than λ/20 by attaching loading capacitors, such that compact circuit size and wide stopband can be achieved. In addition, their circuit models can be equivalent to the bandpass filter prototype. Therefore, the proposed multi-functioal filters can be easily designed using the insertion loss method.
The design of balun bandpass filters is first presented. The design methods for higher order filter response and for introducing transmission zero are proposed. Specifically, balun bandpass filters are implemented using the GaAs pHEMT process with a center frequency of 5.5GHz. The chip sizes are less than 1.5×1mm2 (0.098λg×0.065λg). The measurement results show that the in-band amplitude imbalance and phase difference at the balanced ports meet commercial application requirements. In addition, wide stopband and high selectivity are obtained. The upper stpoband rejection is better than 20dB up to 12f0. Moreover, the proposed balun filter can be further integrated with SPDT switch to achieve highly-integrated RF front-end design.
The second part of the thesis is focused on the design of bandpass power divider. The proposed circuit structure provides good in-band matching and isolation by the introduction of additional isolation resistor and admittance inverters. It can be simply designed by the even-odd mode analysis. Specifically, a third-order integrated bandpass power divider with a center frequency of 5.5GHz is implemented in a chip size of only 1.5×1.5mm2 (0.098λg×0.098λg). In addition, wide stopband and high selectivity are obtained. The upper stpoband rejection is better than 30dB up to 10.3f0. Compared to related previous works, the insertion loss and size are similar to conventional integrated bandpass filters, but two functions are included in the proposed design.
The proposed multi-functional bandpass filters have the advantages of compact size, high selectivity, and wide stopband with simple circuit topology. The complete design procedure and design equations are also proposed. It is believed that this will help reduce the size, cost and design steps of RF front-end.
| en_US |