| Summary: | 碩士 === 國立高雄應用科技大學 === 電子工程系碩士班 === 103 === In this thesis, five filters or multiplexers based on several kinds of commonly used resonators are designed for the front-end module of the wireless communication system. These five circuits include a single-band bandpass filter with a wide stopband, a triplexer, a dual-band bandpass filter with a wide stopband, a tri-band duplexer, and a coplanar waveguide bandpass filter employing graphene material.
A single-band bandpass filter with a wide stopband is proposed. A pair of uniform impedance resonators is employed as the main structure of the filter. Moreover, the special cross-coupling design used to minimize the size of the filter. The microstrip structure is further bended to suppress second harmonic response. According to the experimental result, the proposed bandpass filter has a center frequency located at 0.8 GHz with an insertion loss of 2.20 dB, and a return loss of 17.36 dB. The stopband of the filter is extended up to 4.5 f0 with a rejection level better than 15 dB. The resultant filter meets the 3rd Generation Partnership Project (3GPP) standards or the LTE standards.
A triplexer with compact size is proposed. Three pairs of uniform impedance resonators and a long feed line are employed as the main structure of the filter. Moreover, the special cross-coupling design used to minimize the size of the filter. The long feed line to suppress harmonic response. According to the experimental result, the proposed triplexer has center frequencies located at 0.82/1.85/2.73 GHz with insertion losses of 2.24/1.85/2.75 dB, and return losses of 13.8/12.4/22 dB. The isolation between passbands is about 25 dB. The resultant filter meets the 3GPP standards or the LTE standard.
A dual-band bandpass filter with a wide stopband is proposed. A pair of uniform impedance resonators as well as open stubs are employed as the main structure of the filter. The T-shaped structure using the open stubs is designed to generate transmission zeros. Thus, a filter with better selectivity and suppression of spurious frequencies is achieved. According to the experimental result, the proposed dual-band bandpass filter has center frequencies located at 2.52/4.87 GHz with insertion losses of 1.26/2.53 dB, and return losses of 17.98/11.55 dB. The stopband of the filter is extended up to 3.9 f0 with a rejection level better than 25 dB. The resultant filter meets the IEEE 802.11ac standards or the WLAN standards.
A tri-band duplexer with high rejection level is proposed. Two pairs of uniform impedance resonators and open stubs are employed as the main structure of the filter. Moreover, the duplexer using dual-band bandpass filter is to minimize the size of the filter. The covering coupled-fed is used to improve the coupling capacity and to reduce the insertion losses of the passbands. According to the experimental result, the proposed bandpass filter has center frequencies located at 2.55/2.79/4.87 GHz with insertion losses of 2.14/2.4/2.3 dB, and return losses of 10.7/21.4/14.9 dB. The stopband of the filter is extended up to 3.9 f0 with a rejection level better than 25 dB. The isolation between passband is about 25 dB. The resultant filter meets the WLAN and the WiMAX standards.
Here, we are the first to propose a coplanar waveguide bandpass filter using printed graphene film. According to the experimental result, the frequency response illustrates that the filter is actually a bandpass filter, however, the response shows a poor insertion loss in the passband, which means we are not fully understand the electric properties of the graphene material. There is a lot more work that needs to be done in the future.
|
|---|
