| Summary: | 博士 === 國立中正大學 === 電機工程研究所 === 102 === Wireless microwave systems have enormous impact on modern society. Moreover, the portable devices nowadays are widely adopted in daily life. Furthermore, small size, lighting weight, multiple functionalities, inexpensive cost, high-speed transmission, and beautiful appearance are the current trend. In addition, the RF passive components with multi-band, multi-functional, high-performance, and low cost have increased dramatically. Therefore, the wide passband and broad stopband performances are the main demanding of the passive components, such as filters, baluns, and couplers. In my dissertation, three key components of filters, baluns, and couplers have been proposed with detailed theory and design procedures.
The wide tuning range bandpass filter with a broad stopband is the first design. This filter is composed of two modified coupled lines and one varactor-loaded stub. In terms of measurement, the tunable bandpass filter with the transmission zero within the higher passband skirt has a very wide tuning range, from 0.95 to 1.55 GHz (48%). Moreover, with the return loss greater than 10 dB, there is a controllable constant passband bandwidth 120 MHz. Furthermore, within the tuning range, the insertion loss is from 2.4 to 2.8 dB and the return loss is greater than 20 dB.
The second design is the broadband 3-dB branch-line couplers. The detailed design equations for the branch-line coupler are provided as well. In order to obtain a wide passband, the multi-section branch-lines are utilizing for the proposed 3-dB microstrip branch-line coupler; in addition, the internal impedance levels of branch-line couplers can be reduced to fit the use of microstrip lines. Further, in terms of measured results, there is a wide bandwidth (greater than 70%). Good agreement between theoretical calculation and measurement validates the proposed method.
The third design is a novel wide stopband microstrip balun. The proposed balun is composed of a pair of stepped coupled line and two impedance transformer. The electrical length of each stepped-coupled-line stage is optimize and cascaded together for harmonic suppression. Moreover, the stepped coupled line with weak–strong– weak coupling results in a wide stopband. The agreement between theoretical prediction and measurement validates the proposed structure.
The forth design is the broadband balun. The broadband balun is composed of a wideband power divider and one 180° phase inverter. In order to obtain a broad operating band, the modified impedance transformers are adopted for balun design. A broadband three-stage balun with the coplanar waveguide (CPW) structure has been developed as design examples. Well-matched results of simulation and measurement can validate the proposed approach.
With the advantages of highly integration, four crucial components fabricated on printed circuit board (PCB) have been provided. The proposed filters, baluns, and couplers with compact size, multifunctional, and high performance have been realized, which are suitable for the integrated circuit of modern wireless communication.
|
|---|
