Fully-Metallic Additively Manufactured Monolithic Double-Ridged Waveguide Rotman Lens in the K/Ka-Band

Abstract

This paper reports on the design and experimental validation of a fully-metallic double-ridged waveguide 10 × 10 Rotman lens additively manufactured as a single part. The wide band operation of this quasi-optical beamformer enables us to cover the uplink and downlink frequencies allocated to satellite communications in the K/Ka-band, from 17.3 GHz to 30 GHz. The feeding port design was adjusted to enable vertical printing, thus minimizing the use of supporting structures. A prototype was manufactured and tested. The reported results indicate losses in the range of 0.5 dB in the lower-frequency band and 0.8 dB in the upper-frequency band, including the waveguide transitions added for test purposes. The measured reflection and coupling coefficients remain below −11.5 dB over the operating band. The standard deviation of the residual phase error across the array ports is below 5° in simulation and below 10° in measurements. Array factors synthesized using the scattering parameters confirm the good stability of the beamforming functionality over the wide frequency band analyzed. This monolithic design is a promising step toward more integrated antenna systems, such as a compact dual-stack configuration for planar array design.

Design and fabrication of waveguide‐based graded refractive index Rotman lens with an improved insertion loss at Ka‐band

“…Furthermore, it is noteworthy that the dual-ridged waveguide Rotman lens [32], similar to our own work, does not suffer from dielectric losses. However, it does experience power spillover losses, resulting in reduced energy directed towards the array elements.…”

“…Conventional Rotman lenses also face challenges due to inherent power losses, where a considerable amount of power is dissipated in non-radiating ports, especially dummy ports when input ports are excited. To address these issues, various techniques [22][23][24][25][26][27][28][29][30][31][32] have been utilised to suppress these losses. Tekkouk et al [29] have proposed stacking two layers to create a compact lens with suitable insertion loss but limited to a narrow frequency band.…”

“…To eliminate dielectric losses, Fonseca et al [32] have proposed a Monolithic Double-rigged waveguide-based Rotman lens with high power handling capability at K a -band frequencies. However, due to power dissipation in non-radiating ports, there is a significant insertion loss.…”