Investigation Of All-metal Gap Waveguide Technology With Application To Microwave Passive Power Distribution/synthesis Networks

Constrained by the current semiconductor technology,the output power of a single solid-state power amplifier chip is often challenging to meet application requirements.Therefore,employing power combining/synthesis techniques to combine multiple chips has become one of the primary approaches to achieve high-power sources.Among numerous techniques,circuit-based synthesis utilizing metal waveguides stands out due to its advantage of low loss and is a key means of constructing high-power modules.However,traditional single-conductor waveguides only support TE/TM mode transmission,and their strong dispersion characteristics limit the device’s multi-band applications.On the other hand,currently available waveguide power dividers often incur high manufacturing costs and demand precise assembly levels; otherwise,they may result in significant high-frequency energy leakage.Moreover,in cases requiring high isolation power divider networks,complex waveguide matching structures will further increase the assembly difficulty of the device.Therefore,to obtain more advantageous solid-state power amplifier modules,the current pressing need is to achieve passive synthesis networks that simultaneously possess low loss,ultra-wideband,high isolation,and ease of assembly.To address these challenges,this dissertation progressively explores research based on a novel parallel-plate gap waveguide technology,focusing on four aspects: easy-toassemble ultra-wideband power dividers,high isolation power dividers,dual-frequency high isolation power dividers,and waveguide-to-microstrip transition structures,presenting systematic design schemes.Finally,through the development of a broadband highpower solid-state power amplifier module,the advantages and practical value of the proposed approach are validated.The specific contents are as follows:1.To overcome the limited bandwidth of conventional waveguide power dividers,a ridge gap waveguide ultra-wideband T-junction power divider was designed,achieving over 15 d B return loss simultaneously in three bands(relative bandwidth of 100%).Furthermore,to enhance the bandwidth stability of the device,an embedded pin bed artificial magnetic conductor loading scheme with high assembly robustness was proposed.Experimental results demonstrated significant application advantages of this technique in ultra-wideband power dividers,substantially improving device assembly tolerance to air gaps.2.Addressing the poor isolation of typical T-junction power dividers,two high isolation power divider structures were proposed.Firstly,a ridge gap waveguide T-junction power divider was designed,treating the radiation slot as a matching load,achieving over15 d B isolation without using any physical loads.This compact structure,almost unrestricted by system spatial layout considerations,can accommodate large feed networks.Secondly,a novel waveguide Magic-T encapsulated with a pin bed EBG structure was designed.Tests indicated that this structure can achieve over 15 d B output isolation across the entire band(relative bandwidth of approximately 40%)and 0.7 d B low insertion loss.3.To combine the advantages of high isolation and broadband,a dual-band high isolation power divider investigation has been performed.Initially,a four-port hybrid MagicT was designed,utilizing dual ridge gap waveguides as differential ports and employing microstrip probes for construction and porting.This structure obtained high isolation between power divider output arms and low reflection at each port.Subsequently,to extend the device’s isolation bandwidth,a dual-input impedance loading method was proposed.Finally,by serially connecting T-type microstrips to the sum port of the Magic-T,a fiveport power divider with wideband high isolation(exceeding 15 d B)was achieved,capable of operating in two adjacent bands(relative bandwidth of approximately 75%).4.To enable interconnection between power dividers and solid-state chips for constructing solid-state power amplifier modules,three passive waveguide-to-microstrip transition technologies emphasizing different performance aspects were studied.Firstly,by combining the characteristics of power dividers and probe transitions,a waveguide-MSL dual-probe hybrid Magic-T transition scheme was proposed.When applied in tree-type synthesis networks,it saves half the space for the feeding structure.Secondly,based on the similarity between suspended lines,microstrips,and ridge gap waveguide modes,an efficient interconnection scheme with over 107% bandwidth was proposed.By loading capacitor films,it can also serve as a bandwidth-adjustable reconfigurable transition to adapt to applications in different bands.Thirdly,a ridge gap waveguide-to-microstrip transition based on probe current coupling was introduced,achieving approximately 0.25 d B low loss across a wide frequency range of triple bandwidth.The current coupling mechanism renders this transition highly robust in PCB assembly.5.Development of high-power solid-state power amplifier modules.Based on the aforementioned passive devices combined with active chips,a set of solid-state synthesized amplifier modules was developed for technical validation.Firstly,a group of 16-channel power distribution/synthesis networks was constructed,achieving insertion loss below 1.5 d B in the 6 to 18 GHz(relative bandwidth of 100%)frequency range.Subsequently,detailed descriptions were provided for the assembly of 16 MMICs power amplifier chips and bias circuits,along with active testing of the overall module.Experimental results demonstrated that the module achieved over 120 W continuous wave output power across the C,X,and Ku bands,with a maximum power reaching 160 W.Calculations revealed the synthesis efficiency of the mentioned passive network exceeded 80%,nearing a maximum of 90%.