Short note: Corner reflector antenna

A corner reflector antenna consists of a half-wave dipole (driven element) placed on the bisector of two flat conducting sheets that meet at an angle, usually 90°. The corner reflects the dipole's backward radiation forward, giving a directive beam.

     \  sheet / grid
      \
       \   S
  apex  >-----o dipole  ====> beam
       /
      /   corner angle 90°
     /  sheet / grid

Construction

• Corner angle α: 90° most common (also 60°, 45°).
• Dipole spacing from apex S ≈ 0.25λ–0.7λ (≈ 0.5λ typical).
• Each sheet length ≥ 2S (≈ 1–2λ); sheets are often grids of parallel rods spaced < 0.1λ to reduce weight and wind load.

Working (image theory): for a 90° corner, the two sheets create three images of the dipole (two with opposite current, one with the same). The dipole and its images form a 4-element array whose fields add along the bisector. For α = 180°/n, the number of images is 2n − 1.

Characteristics

• Gain ≈ 10–12 dB over a λ/2 dipole (90° corner, S ≈ 0.5λ); higher for smaller angles.
• Front-to-back ratio high; beamwidth ≈ 40°–60°.
• Input impedance depends on S (≈ 70–150 Ω for S ≈ 0.5λ).
• Linear polarization, moderate bandwidth.

Applications: UHF TV reception, point-to-point VHF/UHF links, radar.