The Researches On Compact Power-Combining Technology Based On Waveguide

With the rapid advancements of the wireless communication technologh in recent years, the demand for high-power solid-state power amplifiers with high efficiency and wide bandwidth has geatly inereased. However, due to the restriction of semiconductor manfacture technics and the difficulties of impedance matching and heat sinking, the output power from an individual solid-state device is rather modest at microwave and millimeter-wave frequencies. So, methods for combining outpout powers from a number of solid-state devices have been extensively studied in order to obtain higher and higher output power. In this article, based on the waveguide-based spatial power combining technology and the traditional quasi-optical power combining technology, several novel campact power combining structures based on waveguide (including the substrate integrated waveguide) have been proposed, and detailed theoretical analysis, electromagnetic simulation and experimental testing have also been carried out. The major achievements are listed as the followings:1. A novel probe-type finline-microstrip coupling unit is presented, and based on this type of coupling unit, a single-layer finline combiner and a double-layer one are proposed. Depending on the PCB (Printed Circuit Board) manufacturing process, the finline, the microstrip probes and the microstrips can be made on the same substrate easily, and the structures of these finline combiners with high combining efficiency are simple. The simple structure of the combiner is suitable to produce in batches.2. Based on the probe-type finline-microstrip coupling unit, a novel traveling-wave coupling unit with iris is presented, and using this traveling-wave coupling unit, a broadband traveling-wave power combiner is proposed. The emphasis in the traveling-wave combiner design is the phase adjustment of different branches. By adding extra meander microstrip lines in traveling-wave finline combiner, the phases of different branches can be adjusted to be coherent and a broadband traveling-wave finline combiner can be achieved. The simulated and measured results indicate that this novel combiner has high power combining efficiency over a wide range of frequency.3. Based on a linearly tapered antipodal finline, a novel low-loss wideband transition between waveguide and substrate integrated waveguide (SIW) is presented. For this novel transition, the E-field is rotated by 90°, and the energy can be transfer from waveguide to SIW. Based on this antipodal finline transition, a novel four-way compact combiner is proposed, and the simulated and measured results indicate that this novel combiner has high power combining efficiency over a wide range of frequency.4. A novel transverse slotted-waveguide combiner is proposed. In this new combiner, the bottom copper of the substrate is used as the top wall of the waveguide, and depending on the PCB manufacturing process, the top wall of the waveguide, the transvers slots and the coupling microstrips can be made on the same substrate easily. Campared with the traditional slotted-waveguide combiner, the fabrication and assembly of the new combining structure is much easier. In addition, a novel connector for the broad walls of two waveguides is proposed, and depending on the choke groove on the substrate, the waveguide, whose borad walls are formed by the bottom copper of the substrate, can connect with the stardand waveguide with good electrical contacts.5. A novel transition between SIW and two microstrips is presented. Depending on the taper-waveguide divider and this novel transition, a novel four-way broadband combiner and an eight-way one are proposed. For these novel combiners, the taper-waveguide dividers can divide the input power into multiple ways, and the double-microstrip to SIW transition can double the number of branches. As well as the compact structures of these combiners and efficient heat singking of MMIC devices, high power combining efficiency is also achieved over a wide range of frequency.6. A novel double-ridged waveguide to microstrip transition is presented. Using this novel transition, a single-side double-ridged combiner and a double-side double-ridged one are proposed, and the simulated and measured results indicate that these novel combiners have high power combining efficiency over a wide range of frequency.7. A novel combiner with tranverse slots on two broad walls of the waveguide is proposed. The bottom coppers of two individual substrates are used as the broad walls of the waveguide. Tranverse slots are eroded on the bottom coppers of the two substrates, and each tranverse slot can couple with two microstrip lines. Thus, a compact four-way combiner with high power-combining efficiency can be formed in a single waveguide, and the fabrication and assembly of the combiner are simple. 8. A four-way planar SIW combiner and a eight-way one are proposed, and the simulated and measured results indicate that these novel combiners have high power combining efficiency over a wide range of frequency. The simple structure of the combiner is suitable to produce in batches.9. Based on the double-probe waveguide-microstrip transition, a novel four-way combiner is proposed. The advantages of this combiner are its potential for high power-combining efficiency and efficient heat singking of MMIC devices.