Researches On Planar Spatial Power-combining Technology

The broad-band, high efficiency and high-power amplifier is an important component of the wireless communication system. But the output power from a single solid-state device is limited and do not meet the requirement of the communication system. Therefore, the high power is obtained through combining output power from many solid-state devices. Among various power combining schemes, the quasi-optical power combining and waveguide-based spatial power combining techniques have developed rapidly recently. They have the advantages of low insertion loss and high combining efficiency and their combining efficiency is roughly independent of the number of amplifier elements. But a majority of spatial and quasi-optical power combiners developed thus far involve three-dimensional circuits that are not easy to handle with respect to both mechanical and electrical aspects. The research for the two-dimensional counterparts of the spatial and quasi-optical combiners has been an important aspect of research on power combining techniques. Based on previous works, several novel planar power combining structures have been presented in this dissertation, and detailed theoretical study, circuit design, electromagnetic simulation and experiment study have been made. The major achievements are listed as the followings:1. The parametric analysis of the power divide-amplify-combine network is performed. The signal in each path can be solved, which allow the failure analysis, combining efficiency analysis et al. Based on the parametric analysis, two kind of symmetrical power dividers are analyzed about their failure performance and the two-path chain power divide-amplify-combine network is analyzed. The failure performance of the single-layer chain power combining amplifier is analyzed and the simulated results can approximately predict the measured results.2. A double-layer planar spatial power divider/combiner is presented. It integrates two single-layer planar spatial power combiners through introducing the transition from the parallel double-strip line to two microstrip lines with the common ground, consequently, and doubles the number of amplifier elements in the roughly equal circuit volume. More amplifier elements can been integrated and higher output power can been obtained. Additionally, employing the double-layer structure makes the characteristic impedance ratio of two ends of the microstrip tapered line halved and a better match can been predicted. The double-layer planar spatial power divider/combiner supports a TEM mode that has no lower frequency cutoff and it can be applied to broad-band power combining.3. A planar chain power divider/combiner is presented. The amplifier chips and their biasing elements can be placed on the side of the circuit through employing right-angle microstrip bend, which makes the space between each signal path can be adjusted according to the size of the amplifier chip. The microstrip-type power dividers with different power dividing ratio are used as the power dividers of the chain power divider. The power dividing ratio is adjusted through changing the characteristic impedance of the microstrip lines. Based on the above works, several improved structures are presented, which have lower insertion loss, excellent heating sinking of the power amplifiers and more uniform power dividing.4. The design method based on the transmission line equivalent model and electromagnetic simulation soft is introduced, emphasizing on the method of optimizing the power dividing and adjusting the phase. The single- and double-layer power divider/combiner and the power combining amplifier constructed on them are designed, fabricated and measured. The measured results demonstrate that the presented structure can combine the output power from amplifier elements efficiently and the design method is effective.5. Two kinds of rectangular-waveguide spatial power divider/combiner with simpler structure are presented. One is basen on the finline-type transition between the rectangular waveguide and the microstrip line. It introduces the two-layer planar chain power divider/combiner into the rectangular waveguide environment,which has a more simple cavity structure and larger number of amplifier elements over the conventional tray-type rectangular-waveguide-based spatial power combiner. Efficient heat sinking of the power amplifiers can be achieved by mounting the devices out of the waveguide. The design method of the transition from the rectangular waveguide to parallel double-strip lines is presented. The total structure is simulated and simulated results are presented. The other is based on the probe-type transition between the rectangular waveguide and the microstrip line. The output microstrip line of the probe-based waveguide-to-microstrip transition is designed having 25-Ohm characteristic impedance, following which a two-path power divider is. Therefore, the number of the signal paths is doubled, but, the volume is not increased remarkably. The total structure is simulated and simulated results are presented.