3D Rotman Lens
Page data
Keywords 3D printing, lens
Authors Sabin Karki
Published 2017
License CC BY-SA 4.0
Page views 518

Basic idea of this project is to design 3D Rotman lens with 3D printing technology that is capable of steering antenna beams in both planes.

Designer[edit | edit source]

Sabin Karki' Aalto University, Department of Electronics and Nanoengineering

Project[edit | edit source]

Planar Rotman lens is a beamforming network commonly used in high frequency. The design equation of the planar Rotman lens can be be easily found in the literature. The lens allows multiple antenna beams to be formed. However, the planar nature of the Rotman Lens limits beam steering in one plane.

Model[edit | edit source]

The 3D Rotman lens consists of three parts: feed ports, lens body and the receiving port.

The planar Rotman lens structure is designed using the design equations from the literature. The design equation gives the shape of the lens body and the position of the feeding and receiving ports, and the length of the receiving port. 3D lens body is generated by rotating the lens curve around the axis. Then the feed and receiving feed lines are designed based on the operating frequency and lens body. Thus, generated feed and receiving ports are positioned on the correct points on the lens surface.

The scad file is well parameterized for frequency, alpha, beta .. etc. except number of feed and receiving ports.

Currently, the PLA material has a dielectric constant of 3. Due to the low dielectric constant, the feed structure itself is radiating. Therefore, printing material of high dielectric constant is desired. Metallization of the feed and receiving port can also solve the problem.

3D Rotman Lens.

Planned upgrades[edit | edit source]

In the design, the receiving antennas are placed based on the planar design principle. Additional, receiving ports needs to be added to make the structure more effective. However, the structure is ready for measurement and simulation purpose.

Bill of Materials[edit | edit source]

The manufacturing cost of 3D Rotman lens is determined by its size. And size is dependent on the material used and operation frequency.

Weight of the 3D Rotman Lens printed with PLA material at various frequencies are:

10 GHz = 45 gram = 1.125 € (PLA price 25€/kg)

30 GHz = 2 gram = 0.05 €(PLA price 25€/kg)

50 GHz = 1 gram = 0.025 € (PLA price 25€/kg)

Additional metallization costs might be required for operation.

Estimated Cost[edit | edit source]

N/A since similar products are not commercially available.

Directions[edit | edit source]

Good understanding of Rotman Lens is preferred for efficient design.

1. Download the OPENscad files from [1] .

2. Parameters can be changed according to requirements.

3. Print 3D Rotman Lens.

Final Prints[edit | edit source]

10 GHz and 50 GHz lens were printed using Lulzbot mini whereas 30 GHz prototype was printed using Formlabs SLA printer. The print speed was set to 50 mm/s, and a layer height of 0.25 mm was used. For a 50 GHz prototype, the surface roughness is high therefore SLA printer is recommended at high frequency.

CAD model, printed part and results[edit | edit source]

<gallery> File:OpenSCAD_model.png|OpenSCAD model of at 10 GHz File:10GHz_30GHz_50GHz.jpg|Printed 3D Rotman Lens at 10 GHz (left), 30 GHz and 50 GHz (right). File:50GHz_Rotman.jpg|Printed 3D Rotman Lens at 50 GHz File:Array_port_phase_3D.png|Numerically calculated phase performance of the 3D Rotamn Lens at 50 GHz <gallery>