Design of a SIW based Hybrid Ring Coupler with Arbitrary Power Splitting Ratio using Gaussian Process Regression

In this paper, the design of a Substrate Integrated Waveguide (SIW) based hybrid ring coupler with arbitrary power splitting ratio employing a Gaussian Progress Regression (GPR) approach is proposed. Arbitrary power splitting is achieved by introducing gradients in permittivity across various sections of the coupler. The gradients in permittivity are achieved by introducing a series of air-holes with appropriate radius and gap. A probabilistic hypothesis for the radius of the air-holes as a function of the required effective permittivity, dielectric constant of the substrate and the gap between the air-holes is derived and proposed using GPR. Hybrid ring couplers with a power splitting ratio of unity, two and four operating in the X-band are designed, simulated, fabricated, and tested using the stipulated design procedure. The designed hybrid ring couplers have an operating bandwidth extending from 9.2GHz to 10.2GHz with a matching $> mathbf{10dB}$, isolation $> mathbf{15dB}$ and a phase imbalance of $pm mathbf{15}^{mathrm{o}}$. The measured splitting ratio for the three couplers are 0dB, 3dB and 6dB respectively with an error of $pm mathbf{0.5dB}$. The measured results for the couplers validate the proposed design procedure.

Design of a SIW based Hybrid Ring Coupler with Arbitrary Power Splitting Ratio using Gaussian Process Regression Conference Paper