Authors: Theunis S. Beukman , Petrie Meyer , Rob Maaskant, Marianna V. Ivashina
Source: FERMAT, Volume 13, Communication 18, Jan.-Feb., 2017
Abstract: The transition from one guided wave to another is important for the integration of different microwave devices. A quadraxial feeding network was recently proposed by the authors ,  for the quadruple-ridged flared horn (QRFH) antenna. This feeding technique allows the excitation of the two orthogonal TE11 fundamental modes in a circular quadridged waveguide (QRWG), required for the wideband dual-polarisation operation of a QRFH antenna.
The differential excitation of the pin pairs in the quadraxial feed is intended for the integration with differential low-noise amplifiers (LNAs). Such a compact solution is attractive for the next-generation radio telescopes which require ultra-low noise performance, hence the necessity for accurate models of the input impedance of the antenna to enable optimal noise matching with the LNAs.
In this work an equivalent circuit model of the quadraxial feed is presented. The circuit is synthesised by only 3 unknowns and achieves accurate input impedance for a wide range of dimensions. This model gives insight into the operation of a quadraxial feed and allows fast synthesis of optimal feeding designs that would ensure a strong excitation of the desired mode at the input of a QRFH.
Index Terms: Ultra wideband antennas, quadruple-ridged waveguides, waveguide transitions, equivalent circuits.
View PDFEquivalent Circuit of a Quadraxial Feed for Ultra-Wide Bandwidth QuadrupleRidged Flared Horn Antennas