Research And Design On Multiple-band Microstrip Filtering Fusion Circuits

With the rapid expansion of the Internet and wireless communication,microwave circuits and systems have been paid more and more attention by researchers from all walks of life.Facing more and more finely divided frequency spectrum,the design of multi-frequency components and circuits become a research hotspot.Multi-passband filtering functional device is a device that integrates multi-band filtering function simultaneously,which can filter interference signals as well as inter-modulated or harmonic signals generated by nonlinear devices at several key nodes in the front end of RF circuits.This thesis mainly studies and designs high-selectivity multi-band filter,high-isolation multi-band filter power splitter and multi-band switchable active cold and hot noise source.The main contents of the thesis are:1.A novel octo-band bandpass filter utilizing an unequal-width cruciform connected resonator with open-and short-stub is proposed.In addition,the short-stub is constructed by Yshaped short-stubs with unequal characteristic admittances connected in parallel,which enhances pole and zero tunability further.The octo-band bandpass filter,utilizing a simple structure,obtains a low insertion-loss,and also features sharp skirt and deep isolation between passbands.2.Based on the novel symmetrical X-shaped resonators,combining coupling feeder and two isolation resistances,a quad-band filtering power divider is implemented with highisolation and low insertion-loss.Each X-shaped resonator adopts four alternately arranged open-and short-stub,which makes each passband achieves two poles and zeros,so the passband is characterized by high selectivity and low insertion loss.Due to the addition of coupling feeder,better suppression at stopband and isolation is obtained.3.Employing only one single broadband active cold load based on a heterojunction bipolar transistor and two switches,a switchable cold and hot noise temperature output is obtained.With a connected microstrip,each switch also introduces one transmission zero between two passbands,which improves the passband selectivity and stopband suppression.Thus,a dualband switchable cold and hot noise source is implemented.The high-performance multi-band filter,high-selectivity multi-band filter power divider and multi-band switchable active cold and hot noise source are particularly suitable for applications in multi-service and multi-band communication systems.