Research On Miniaturized Multifunctional Integrated RF Circuits

RF circuits are the key parts of the radar,communications,electronic countermeasures,and remote sensing systems.With these systems having the growing demands of better performance,higher integration and multifunction,higher requirements are put forward for RF circuits.This dissertation targets at achieving the miniaturized multifunctional RF circuits and components,microwave receive modules,and filtering antennas,based on the National Natural Science Foundation Project and pre research projects concerning the digital array and microwave communication systems,etc.A series of key technologies and design techniques have been studied and applied in the development of several systems.The main works of this dissertation are listed as follows:1.The novel filter schematic with the characteristics of wide passband,low insertion loss and high selectivity is proposed,by employing the inductive input/output structure,feedback capacitor and parallel resonator.The working mechanism of the filter schematic is revealed both graphically and mathematically.The three-dimensional physical implementations of the inductors and capacitors in the schematic are studied and accomplished based on Low Temperature Co-fired Ceramic(LTCC)technology.By using the novel filter schematic and LTCC components,a prototype of the compact lumped-element bandpass filter is developed in a multilayer LTCC substrate,showing extremely small size and good electrical properties.The simulated and experimental results demonstrate that the filter achieves a wide fractional bandwidth of 62% with remarkably low insertion loss,when obtains a great selectivity and outof-band performance.2.A miniaturized lumped-element 3 d B quadrature hybrid is proposed based on LTCC technology.The hybrid has a compact structure and good electrical performance.The simulated and experimental results show that,within the 33% operating band,the hybrid achieves good coupling and transmission properties,good phase balance,as well as high isolation.3.The novel compact bandpass filter structure using stub-loaded T-shape resonator with source-load coupling is proposed,having wide passband and controllable transmission zeros.The working mechanism of the structure is revealed by taking the circuit theory analysis and several parametric studies.Based on the proposed filter structure,a prototype of the bandpass filter is implemented in a multilayer LTCC substrate and verified experimentally.The filter achieves a low-loss wide passband,high selectivity and excellent out of band suppression performance simultaneously with an uncomplicated geometry.The filter has also been integrated into our microwave receive module,as the RF front-end bandpass filter.4.An X-band integrated 4-unit microwave receive module based on LTCC technology is presented for the system trend of high-integration and multifunction.A prototype of the module is fabricated,assembled,and tested.The experimental results show that the proposed receive module achieves several functions including X-band space signal receiving,filtering,amplifying and down converting,in a small and highly-integrated structure.Within the promising wide operating frequency band,the proposed receive module exhibits high receiving gain,high image frequency suppression,strong antijamming capability and stable intermediate frequency output.5.In order to meet the system demands on miniaturization,high-integration and low loss,as well as reduce the mutual coupling between different frequency bands,the novel collaborative and multifunctional-fusion design method of dual-polarized filtering antenna is proposed for obtaining the bandpass filtering radiation in a low-profile structure.Comprehensive field and circuit analysis as well as parametric studies are conducted by using the three-dimensional electromagnetic full wave simulator.Based on the proposed design method,three low-profile dual-polarized filtering antenna prototypes with different physical structures are developed.The simulated and experimental results demonstrate that all of these three antennas have a wide operating frequency band,covering the entire 5G Sub-6 GHz N77(3.3-4.2 GHz),N78(3.3-3.8 GHz),and N79(4.4-5.0 GHz)bands.Within the operating band,high gain,good radiation performance,low cross polarization level and high isolation between two polarization ports are obtained.Besides,good out-of-band radiation suppression and high selectivity are realized.