---
title: "Short note: Corner reflector antenna"
subject: "Propagation and Antenna"
chapter: 3
key: "semester_6/propagation_and_antenna:corner-reflector-short-note"
source: https://www.bctengineer.com/q/semester_6/propagation_and_antenna/corner-reflector-short-note
site: BCT Engineering
---

# Short note: Corner reflector antenna

Propagation and Antenna · Chapter 3: Antenna Classification

- Asked in: 2076 Baisakh, 4 marks
- Video: [Reflector Antenna and its Types - Corner Reflector](https://www.youtube.com/watch?v=BdYp7FdJpyU) — Padmasri Naban
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_6/propagation_and_antenna/corner-reflector-short-note
- Whole chapter: https://www.bctengineer.com/md/semester_6/propagation_and_antenna/chapter-3

## Question

Write a short note on corner reflector antenna.

## Short answer

A corner reflector antenna places a half-wave dipole at the bisector of two conducting sheets forming a 90° corner. Image theory creates three images, yielding a 4-element array with high directivity along the bisector. Typical gain 10–12 dB over dipole, beamwidth 40°–60°, used for UHF TV and point-to-point links.

## Answer

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.

```text
     \  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.

## Check yourself

The answer's key points as multiple-choice questions, with the correct option and why.

1. What does a corner reflector consist of?
   A. A helix on a plate
   B. A loop in a box
   C. A horn and lens
   D. A half-wave dipole on the bisector of two conducting sheets meeting at an angle
   Answer: D. A dipole sits on the bisector of two flat sheets, commonly at 90 degrees. (Key point: Construction)

2. For a 90 degree corner, how many images of the dipole form?
   A. Three
   B. One
   C. Two
   D. Four
   Answer: A. Number of images is 2n-1 with alpha = 180/n; n = 2 gives 3. (Key point: Images)

3. What gain over a dipole does a 90 degree corner give?
   A. About 0 dB
   B. About 10-12 dB
   C. About 30 dB
   D. Less than a dipole
   Answer: B. Fields of dipole and images add along the bisector. (Key point: Gain)

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