---
title: "Types of antenna diversity compared"
subject: "Wireless Communication"
chapter: 5
key: "semester_7/wireless_communication:antenna-diversity-comparison"
source: https://www.bctengineer.com/q/semester_7/wireless_communication/antenna-diversity-comparison
site: BCT Engineering
---

# Types of antenna diversity compared

Wireless Communication · Chapter 5: Equalization and Diversity

- Asked in: 2071 Magh, 4 marks
- Video: [Diversity Techniques in Antennas / Wireless Communication | Antenna and Wave Propagation Module - 6](https://www.youtube.com/watch?v=jJhxMI3jvi0) — THE BACKBENCH ENGINEERING COMMUNITY
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_7/wireless_communication/antenna-diversity-comparison
- Whole chapter: https://www.bctengineer.com/md/semester_7/wireless_communication/chapter-5

## Question

Discuss and compare different types of antenna diversity technique.

## Short answer

Space diversity uses separated antennas, offering lowest correlation and highest gain but needs physical spacing. Polarization diversity uses co-located orthogonal polarizations, compact with slight gain reduction. Angle diversity employs directional beams, useful indoors. Space gives best performance; polarization is common at base stations due to compactness.

## Answer

**Antenna diversity** uses more than one antenna to obtain independently faded copies of the signal. The main kinds are:

1. **Space diversity** – identical antennas physically separated (≈ λ/2 at the mobile, 10λ or more at the base station) so fading is uncorrelated.
2. **Polarization diversity** – two co-located antennas with orthogonal polarizations (V/H or ±45°); multipath scattering makes the two polarizations fade differently.
3. **Angle (pattern) diversity** – directional antennas or beams pointing in different directions, receiving different groups of multipath waves.

Space diversity outputs are combined by selection, feedback, maximal ratio or equal gain combining.

| Feature | Space | Polarization | Angle/pattern |
|---|---|---|---|
| Basis | Different location | Orthogonal polarization | Different direction |
| Antenna size | Large (separation) | Compact, one mast | Moderate |
| Correlation | Lowest | Low–moderate | Moderate |
| Diversity gain | Highest | Slightly lower | Depends on angular spread |
| Branches | Any number | Usually 2 | Several beams |
| Main use | BS and mobile | BS (cross-pol panels) | Indoor, smart antennas |

**Summary:** space diversity gives the best gain but needs room; polarization diversity gives most of the gain with a single compact antenna, so it is common on modern base stations.

## Check yourself

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

1. Which are the antenna diversity types?
   A. Time, frequency, code
   B. Selection, MRC, EGC
   C. Space, polarization, angle (pattern)
   D. LMS, RLS, ZF
   Answer: C. All obtain independently faded copies with antennas. (Key point: Antenna diversity kinds)

2. Polarization diversity uses...
   A. Widely separated identical antennas
   B. Beams in different directions
   C. Different carriers
   D. Co-located antennas with orthogonal polarizations
   Answer: D. V/H or +-45 degrees. (Key point: Polarization)

3. Which gives highest diversity gain?
   A. Space diversity
   B. Polarization diversity
   C. Angle diversity
   D. All equal
   Answer: A. But it needs room for antenna separation. (Key point: Best gain)

4. Why is polarization diversity common on modern base stations?
   A. Highest gain of all
   B. Most of the gain from one compact antenna
   C. No cost
   D. Needs 10 lambda
   Answer: B. Cross-pol panels save space. (Key point: Why polarization common at BS)

## Related in Wireless Communication

- [Feedback vs maximum ratio combining diversity](https://www.bctengineer.com/question.md?key=semester_7%2Fwireless_communication%3Afeedback-vs-mrc-diversity) — Wireless Communication, chapter 5
- [Need for diversity; maximum ratio combining](https://www.bctengineer.com/question.md?key=semester_7%2Fwireless_communication%3Adiversity-need-mrc) — Wireless Communication, chapter 5

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