Trihedral Corner Reflector

The goal was to build trihedral corner reflectors to be used in a radar training accompanying the lecture "Fundamentals and Systems of Radar Technology". This lecture is offered by the "Radio Technologies for Automated and Connected Vehicles" research group.

1. Analysis

A trihedral corner reflector is basically made of three equal right-angled triangles. The first task was to define the length a of the legs (cathetus).

The reflector shall work in a frequency range of 77 GHz to 81 GHz. This corresponds to wave lengths of approximately 3.7 mm to 3.9 mm. Hence, any leg length a that is significantly larger than 3.9 mm is will be okay. However, the corner reflector shall still be handy and lightweight such that anyone can hold it easily.

If f is the frequency, and c₀ is the speed of light (in vacuum), the radar cross-section (RCS) σ can be computed as follows.

We chose a = 69 mm which results in an RCS σ ≈ 6.6 m² (exact: 6.5932... m²). We chose this value since the rounded RCS (6.6 m²)(rounded to one decimal place after the comma) would require a leg length of 69.017 mm, which is sufficiently close to 69 mm. Additionally, 69 mm is more than 10 times larger than the maximum wavelength of 3.9 mm.

2. Building a jig

The final reflector is made of copper-coated plates that can be used to create PCBs. For each reflectorm, three right-angled triangles are have to be cut out and glued together. To make the glueing process easier, we first designed and 3d-printed a jig.

The jig has several cutouts. These are used to glue the triangles together. The jig is made for plates of 1.6 mm thickness. The FreeCAD files and STL files are attached to this page.

3. Cutting the triangles

ToDo

4. Glueing the triangles

ToDo