| In recent years,with the rapid development of military and civilian wireless communication technology,the available spectrum resources have become increasingly tight,at the same time,the wireless communication technology has developed from traditional microwave communication to higher frequency millimeter wave communication.As one of the millimeter-wave frequency bands,the W-band has been widely used in radar and guidance,electronic countermeasures,automobile collision avoidance and other systems due to its short wavelength,wide frequency band,and rich spectrum resources.As an important part of the W-band radar system,the W-band RF front-end passive circuit directly determines the performance of the entire radar system.Therefore,it is of great significance to develop high-performance and low-cost W-band RF front-end passive circuits for national defense,economy and people’s livelihood.In this dissertation,on the basis of the traditional rectangular metal waveguide structure,the design and realization method of the miniaturized and low-cost W-band filtering single-pole double-throw(SPDT)switch,W-band E-plane waveguide filters and W-band waveguide filtering power divider are discussed under the application background of modern W-band radar RF front-end system with low insertion loss and low-cost.The main work can be summarized as follows:1.In order to realize the miniaturization,low cost and filtering characteristics of the W-band SPDT switches,the improved SPDT switchs and the filtering SPDT switches are designed in this paper.Firstly,the improved PIN diode SPDT switch is designed based on the hybrid integration process.Secondly,the improved SPDT switch is fabricated and measured.The measurement results verifies the feasibility of the improved SPDT switch.At the same time,the accurate forward and reverse bias impedance parameters of PIN diode are extracted according to the measurement results.Finally,on this basis,the W-band SPDT switch with filtering characteristics is designed by combining the main circuit of the improved SPDT switch and the double-ridged fin line filtering transition structure in this paper.2.To solve the problems of large volume,poor shape factor,high cost and difficulty in mass production of the traditional W-band E-plane waveguide filter,the novel structure of E-plane waveguide bandpass filter is proposed.The proposed method utilizes the high-pass characteristic of the rectangular waveguide,at the same time,the multiple transmission zeros are introduced because the dielectric substrate with different resonant cells is inserted into the E-plane of the waveguide.Moreover,this zeors are appropriately set in the upper and lower stopbands to achieve the effect of a band-pass filter.The transmission zeros can be independently controlled by the corresponding resonant cell.Therefore,changing the size of the resonant cell can flexibly adjust the bandwidth of the E-plane waveguide bandpass filter.Due to the introduction of the transmission zeros in the upper and lower stopbands,the out-of-band suppression and shape factor of the bandpass filter has been effectively improved.In order to verify the flexible and controllable bandwidth of the proposed W-band E-plane waveguide bandpass filter with high-performance,the different bandwidth and center frequency of the bandpass filters were designed,and the processing consistency measurement was carried out.When the center frequency is 96.75GHz,the measured minimum insertion loss of the filter is 1.02dB,the 3dB bandwidth is 6.5%,the in-band return loss is greater than 14dB,and the shape factor is 1.51;its volume is 3.21×1.27×0.127mm~3.The measured results show that the relative bandwidth and center frequency of the proposed E-plane waveguide bandpass filter can be adjusted flexibly without increasing the overall volume of the circuit structure,and it can meet the requirements of low cost and miniaturization.3.The novel structure of the W-band E-plane waveguide single-pass bandpass filter based on a single beeline resonator is proposed.According to the principle of using the transmission zero to design the bandpass filter,the multiple transmission zeros are generated because the dielectric substrate with a single compact beeline resonator(CBR)is inserted into the E-plane of a standard rectangular waveguide.Therefore,the miniaturized W-band single-pass bandpass filter with high-performance is designed based on the single CBR.The center frequency,bandwidth and return loss of the proposed single-pass bandpass filter can be independently adjusted by simply changing the size of the CBR.In addition,due to the introduction of the transmission zeros,the designed bandpass filter has high out-of-band rejection and good shape factor.The proposed single-pass bandpass filter realizes compact size and high performance,while its center frequency,bandwidth and return loss can be controlled independently.When the center frequency is 88.55GHz,the measured minimum insertion loss of the filter is1.2dB,the 3dB bandwidth is 3.6%,the in-band return loss is greater than 18dB,and its volume is 3.21×1.27×0.127mm~3.Based on the single-pass bandpass filter,the W-band E-plane waveguide double-pass bandpass filter is designed by using the CBR and uniform impedance resonant cell(UIRC),its volume is 3.21×1.27×0.127mm3.The bandwidth of each passband of the proposed dual-pass bandpass filter can be adjusted independently.The dual-pass bandpass filter realizes compact size and easy processing,while its structural design is very flexible.4.To solve the problems of poor isolation and difficulty in connecting with the plane of the traditional W-band waveguide power divider,the improved W-band waveguide power divider is proposed.Combining the traditional waveguide-to-microstrip transition structure theory with the principle of using the transmission zeros to design the bandpass filter,the design method of the waveguide-to-microstrip probe transition structure with filtering function is proposed.Compared with the traditional waveguide-to-microstrip probe transition structure,the proposed filtering transition structure not only keeps the size basically unchanged,but also realizes the dual functions of filtering and transition.Due to the introduction of the transmission zeros,the proposed transition structure has good filtering characteristics and out-of-band suppression characteristics,which opens up a new design idea for realizing the waveguide-to-microstrip filtering transition structure with highly selectivity.Based on the experimental verification of the characteristics of the W-band transition structure with filtering function,the W-band waveguide filtering power divider is designed by combining the power divider with the transition structure.In the frequency range of 88.3 to 94.4 GHz,the measured insertion losses of the waveguide filtering power divider are less than 1.6 dB,and its return losses are greater than13dB.The proposed waveguide filtering power divider realizes the dual functions of power division and filtering,while it broadens a new technical approach for the design of multiple functions in a single waveguide device.The filtering power divider not only has good application prospects in the modern W-band radar RF front-end system,but also verifies that the filtering transition structure has good engineering application value in practical circuit design. |
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