5-way radial power combiner at W-band by stacked waveguide micromachining

Highlights: • Radial power combiner in W-band with high-performance based on the TE₀₁ circular waveguide mode. • Systematic design process of both components of the combiner: the transducer and the N-way radial divider. • The manufacturing process using high precision micromachining with stacked waveguides has led to the excellent performance. • Experimental results validate the state-of-art electrical response of the 5-way power combiner in W-band. This work presents a 5-way radial power combiner using the very low loss TE₀₁ circular waveguide mode with a performance in the state of art for W-band. The accomplished design shows excellent characteristics: the experimental prototype has a return loss better than 20 dB, with a balance for the amplitudes of ($\pm$0.4 dB) and ($\pm 3.5^o$) for the phases, in a 12.8% fractional bandwidth (12 GHz centered at 94 GHz). In order to obtain these specifications, required for instance in plasma diagnosis systems or in power amplifiers, a meticulous step-by-step procedure is developed for both, the design and the challenging manufacture at W-band by stacked waveguide micromachining. The first step involves the design of a mode transducer, from the TE₁₀ mode in the rectangular waveguide to the low-loss TE₀₁ mode in the circular waveguide, with very high purity. In the second step, a 5-way radial power divider is designed. These designs, in order to be successful, have incorporated all the constrains for the manufacturing at W-band, using an E-plane stacked waveguide arrangement for low losses. The power combiner, made up by the transducer and the divider, has been manufactured with great accuracy using a very challenging assembly process, providing experimental results in very good agreement with the theoretical results.