Millimeter-wave Spatial Power Combining Based On Modified Luneberg Lens

High power source is one of the key components of millimeter-wave system. With the rapid development of various application system, more demands are put forward to force the source to achieve better performance. However, neither traditional vacuum electronic device or single solid-state device can satisfy the application standard, because of large volume and limited output power, respectively. As one of the effective ways to obtain high power source, spatial power combining technology has the advantages of higher combining efficiency and larger output power, which makes it very competitive and attractive for practical applications.Spatial power combining technology based on modified Luneberg lens is proposed in this paper. Using the focusing characteristics of Luneberg lens, power amplification and combining are realized in the waveguide. In this paper, the effect on combining efficiency caused by amplitude and phase errors are studied theoretically. Modified air-filled Luneberg lens is also designed in this paper. Besides, waveguide-to-microstrip transition, one-way and back-to-back combining structures are simulated and measured. The main achievements of this paper is listed below:1) Measured results of the designed power amplifier circuit agree with the requirements, which verify the rationality of bias circuit design.2) Two kinds of waveguide to microstrip transition are designed, and the antipodal finline with excellent broadband performance is manufactured and measured. It has the advantage of simple structure and small size, which has a length of about0.6λg and results in low insertion loss. The measured insertion loss of the manufactured back-to-back finline structure with a length of45mm is lower than1.2dB all over the frequency band from28GHz to32GHz.3) The combining structure based on modified Luneberg lens proposed in this paper solves the problem that feed can not be placed at the lens focus, and also broads the design scope of lens parameters. The lens is air-filled, with no dielectric materials, therefore free of dielectric loss. As a result, the measured insertion loss of manufactured back-to-back structure is relatively low, and the combining efficiency can achieve95.5%at30GHz.4) The finline array is applied to the back-to-back power combining system. The measured2dB insertion loss bandwidth of manufactured back-to-back system is about1GHz, and1.13dB is obtained at30GHz.