Analysis, Construction and Evaluation of a Radial Power Divider/Combiner

Abstract

Radial N-way combiners and dividers are efficient and compact structures for power combining and dividing, which combines or divides the power of N inputs in one single step. The use of this method results in low losses and therefore presents an interesting alternative to often used combiner and divider networks, such as binary tree structures consisting of 2- or 3-way splitters. In this thesis project, the construction of radial N-way cavity combiners and dividers is analysed and an 8-port TM020 cylindrical cavity combiner/divider with SMA-connector input and output ports is designed and fabricated. The characteristics of the fabricated prototype is evaluated and compared to the simulated design. The average return loss at the peripheral ports is higher than 18.4 dB and the return loss at the centre port is higher than 17.6 dB for a 10 % bandwidth around the centre design frequency of 3.1 GHz. The measured insertion loss is lower than 0.16 dB for the same band. The divider and combiner are used in an active test setup with 8 InGaP HBT amplifiers, by which a study of degradation in the event of amplifier failure is performed. Methods to reach a more graceful degradation are discussed. The thesis report also presents a brief overview of different types of N-way combiners and a comparison between the characteristics of some published designs. In conclusion, radial N-way combiners are a very attractive alternative for combining in high power systems due to their low-loss performance and the gradual loss of power in the event of amplifier failure. If they are used together with solid state power amplifiers, they can be used to replace other high power RF amplifier solutions such as the travelling wave tube amplifier.