---
title: "Short note: Microstrip (printed) antenna"
subject: "Propagation and Antenna"
chapter: 3
key: "semester_6/propagation_and_antenna:microstrip-antenna"
source: https://www.bctengineer.com/q/semester_6/propagation_and_antenna/microstrip-antenna
site: BCT Engineering
---

# Short note: Microstrip (printed) antenna

Propagation and Antenna · Chapter 3: Antenna Classification

- Asked in: 2079 Chaitra, 3 marks; 2078 Chaitra, 3 marks; 2073 Bhadra, 3 marks (asked 3 times)
- Video: [Microstrip Patch Antenna | Construction and Design |Aperture Antenna Basics](https://www.youtube.com/watch?v=EKOecXPypvw) — Professor Rekt
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_6/propagation_and_antenna/microstrip-antenna
- Whole chapter: https://www.bctengineer.com/md/semester_6/propagation_and_antenna/chapter-3

## Question

Write a short note on microstrip (printed) antenna.

## Short answer

A microstrip antenna is a metal patch on a dielectric substrate above a ground plane. Radiation comes from fringing fields at two edges acting as slots, giving a broadside beam. It is low profile and cheap but has narrow bandwidth and gain of 6–8 dBi.

## Answer

A **microstrip (patch or printed) antenna** is a thin metallic patch etched on one side of a dielectric substrate whose other side is a ground plane. It is made by printed-circuit techniques.

```text
        patch (L x W)
     _______________
    |_______________|___ feed line
 ///////////////////////////  substrate εr, h
 ===========================  ground plane
  fringing fields at the two radiating edges
```

**Construction and working**
- Patch shapes: rectangular, square, circular, triangular. Substrate εr ≈ 2.2–12, height h ≈ 0.003λ–0.05λ.
- The patch behaves as a cavity; for the dominant mode its length is about half a guided wavelength:

```text
L ≈ λ₀ / (2√εr)   (slightly less, due to fringing)
```

- Radiation comes from the **fringing fields** at the two open edges, which act like two slots in phase; the beam is broadside (normal to the patch).

**Feeding methods**: microstrip line (inset), coaxial probe, aperture coupling, proximity coupling.

**Advantages**: low profile, light, cheap, conformal to curved surfaces, easy to integrate with circuits and to form arrays, linear or circular polarization possible.

**Disadvantages**: narrow bandwidth (≈ 1–5 %), low efficiency and gain (≈ 6–8 dBi), low power handling, surface-wave losses.

**Applications**: mobile phones, GPS, Wi-Fi, RFID, aircraft and missile antennas, satellite terminals.

## Check yourself

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

1. Radiation from a microstrip patch comes from
   A. fringing fields at the two open edges
   B. the ground plane current
   C. the substrate itself
   D. the feed line only
   Answer: A. The edges act as two in-phase slots giving a broadside beam. (Key point: Source of radiation)

2. For the dominant mode, patch length is about
   A. lambda0
   B. lambda0 / (2 sqrt(er)), slightly less due to fringing
   C. 2 lambda0
   D. lambda0 sqrt(er)
   Answer: B. The patch is roughly half a guided wavelength long. (Key point: Patch length)

3. A main disadvantage of the microstrip antenna is
   A. heavy weight
   B. very wide bandwidth
   C. narrow bandwidth (about 1-5%)
   D. high power handling
   Answer: C. Narrow bandwidth, low gain and low power handling are its drawbacks. (Key point: Disadvantage)

## Related in other subjects

- [Stub matching for antenna with Γ = 0.33∠66°](https://www.bctengineer.com/question.md?key=semester_7%2Frf_and_microwave_engineering%3Amicrostrip-antenna-stub-matching) — RF and Microwave Engineering, chapter 2