This article proposes a ray-tracing and physical-optics (RT-PO) model that allows for an accurate and time-efficient evaluation of planar Mikaelian lens antennas implemented by parallel plate waveguides (PPWs). With an intrinsic flat shape and axis-symmetry of refractive-index distribution characteristics, the planar Mikaelian lens antennas are easy to fabricate and integrate into standard planar feeds. A numerical computation of the ray paths based on Snell's law describes the phase of the electric field in the lens aperture, while the ray-tube power conservation theory is employed to evaluate the amplitude. The field equivalence principle is then used to calculate the far-field of the lens antenna. The information on far-field directivity, gain, and dielectric efficiency is further obtained, considering a small loss in the dielectric materials. Our approach is validated by comparing the results of a particular Mikaelian lens antenna with those computed using a commercial full-wave simulator, demonstrating high accuracy and a significant reduction in computation resources and times.

The Physical Optics (PO) method is used to derive simplified expressions to compute the radiation electric fields of planar graded-index and geodesic lenses based on a parallel-plate waveguide (PPW) implementation. If the PO method is combined with ray-tracing (RT) techniques, the resulting RT-PO procedure is capable of computing radiation patterns and gain of the PPW-based lens antennas when their apertures have a general shape and the electric field is vertically polarized. The RT-PO method is validated by comparing it with the full-wave simulation results of the commercial software ANSYS HFSS for three application cases. The results show that the RT-PO approach is not only very efficient from a computational point of view but also accurate, thus being a very convenient analysis/design tool for this kind of antenna.

This article describes a detailed procedure that allows for a time-efficient design of fully metallic geodesic H-plane horn antennas using an in-house ray-tracing method together with an optimization algorithm. With all the propagation in the air, geodesic H-plane horn antennas are of low loss and highly efficient. The proposed geodesic H-plane horn antennas provide a new degree of freedom, the height profile, to alleviate phase errors, realizing high gains and aperture efficiencies. Optimizations are implemented to design the height profile for a given target, enabled by the highly accurate and time-efficient in-house ray-tracing model. To demonstrate the correctness and versatility of the proposed design procedure, two prototypes are manufactured with computerized numerical control (CNC) machining and compared to their planar counterparts, with the aim of a high increased gain and aperture efficiency, respectively. The prototypes maintain good frequency stability from 26 to 33GHz, with sidelobe levels lower than -15dB and return loss better than 15dB. The first prototype improves the realized gain by over 5dB compared to the reference horn, while the second prototype achieves an aperture efficiency of around 65% within the operating frequency band.

In this contribution, we provide an experimental validation of a ray-tracing and physical-optics model for geodesic horn antennas. The proposed model employs a ray-tracing technique to obtain electric fields in the horn aperture and applies the field equivalence principle in physical optics to evaluate the three-dimensional radiation characteristics of the geodesic horn antennas. The numerical results agree well with the measurements in terms of radiation patterns in the uv-plane, the principal E- and H-plane patterns, and directivities.

Additive manufacturing (AM) is growing as a key technology for the miniaturization and integration of microwave components. Among several AM processes, laser powder-bed fusion (LPBF) is especially convenient for waveguides and horns because it allows for 3-D printing of metal-only parts with high accuracy and low surface roughness. During the 3-D printing process, metallic powder materials are selectively consolidated by melting layer by layer together using a heat source, that is, a laser, allowing for adaptation to complex and shaped structures. The present study investigates the feasibility of using LPBF-AM to fabricate waveguides and geodesic $H$ -plane horns in $V$ -band. Geodesic $H$ -plane horns comprise two parallel curved metallic plates to reduce phase errors and achieve high gain and aperture efficiency, and are particularly suited to be fabricated using LPBF. The monolithic waveguides demonstrate significantly better performance than their two-piece counterparts, achieving an average attenuation coefficient of 5.3 dB/m for the straight waveguide and 8 dB/m for the 90 $^\circ$ $E$ -plane waveguide bend at 50-70 GHz. Similarly, the monolithic geodesic $H$ -plane horn has higher realized gains and radiation efficiencies with only a sixth of the weight compared to the two-piece version at 52-68 GHz. The results demonstrate that the LPBF-AM technique is a promising candidate to produce monolithic metal-only microwave components in $V$ -band.

A compact and lightweight geodesic H-plane horn antenna is designed and experimentally validated in the W-band. Two corners in the aperture of the horn are truncated to increase aperture efficiency and reduce the weight and volume of the antenna. The prototype was monolithically printed in AlSi10Mg through laser powder-bed fusion additive manufacturing, resulting in a weight of only 14 g. The prototype maintains good frequency stability from 75 to 110 GHz, with sidelobe levels lower than −25 dB and return loss better than 15 dB. The measured data show a realized gain of 20 dBi with an aperture efficiency of around 60% (calculated using realized gain) and an estimated radiation efficiency of better than 70%.