1. Core Concept of Antenna Gain
Definition: Antenna gain describes an antenna’s ability to focus electromagnetic-wave signals for transmission and reception. Its unit is dBi.
Simplified explanation: An antenna cannot increase signal power out of nowhere. It only concentrates scattered signal energy toward specified directions to achieve longer transmission distance and stronger signal.
Core Rules
- Higher gain → longer transmission distance, stronger directivity, narrower beam width
- Lower gain → wider signal coverage, uniform 360-degree radiation, larger coverage angle
- Lower frequencies are difficult to achieve high gain due to long wavelength and limited antenna size
- Higher frequencies can realize high gain more easily because short wavelengths help focus beams
2. Two Categories of Antenna Gain
2.1 Passive Antenna Gain (General RF Antennas)
It relies purely on physical radiation without circuit-based amplification. Rod, magnetic-mount, fiberglass, FPC and panel antennas are all passive antennas. Typical gain range: 0-15 dBi.
2.2 Active Antenna Gain (GNSS-Only)
Equipped with a built-in LNA (Low-Noise Amplifier). The published gain includes circuit amplification and does not represent pure radiation gain of the antenna element itself. GPS / Beidou dome antennas are active antennas, with gain of 20-28 dBi.
3. Standard Gain for Different Antenna Types
3.1 Internal Antennas (Low Gain, Short–Range)
- FPC flexible antenna: 0-2 dBi
- PCB onboard antenna: -2-1 dBi (lowest gain, for short-range indoor applications)
- Ceramic antenna (2.4G / GNSS): 0-3 dBi
3.2 General External Omnidirectional Antennas (For Common IoT)
- Rod antenna: 2-5 dBi (most widely used, cost-effective)
- Standard small magnetic-mount antenna: 2-5 dBi
- Extended large magnetic-mount antenna: 5-8 dBi (longer transmission distance)
- Blade / flat antenna: 3-6 dBi
3.3 Outdoor High–Gain Omnidirectional Antennas
- Fiberglass omnidirectional antenna: 6-12 dBi (for LoRa base stations and large-area outdoor coverage)
3.4 High-Gain Directional Antennas (Long-Range Point-to-Point)
- Directional panel antenna: 6-15 dBi
- Yagi antenna: 8-15 dBi (long-range narrow-beam scenarios)
3.5 UHF-RFID Dedicated Antennas
- Standard RFID panel antenna: 6-8 dBi
- High-gain RFID antenna: 912 dBi (longer read-write distance, improved multi-tag batch reading performance)
3.6 GNSS Positioning Antennas
- Passive ceramic antenna: 0-3 dBi
- Active dome antenna: 20-28 dBi (built-in amplifier for high positioning sensitivity)
4. Typical Gain Range for IoT Frequency Bands
- 315 MHz / 433 MHz: 2-5 dBi (practical limit for low-frequency bands; ultra-high gain is unachievable)
- LoRa 470-510 MHz: 2-6 dBi; up to 8 dBi for outdoor fiberglass antennas
- NB-IoT / 2G / 4G: 2-5 dBi; 5-8 dBi for extended magnetic-mount antennas
- 2.4 GHz (WiFi / Bluetooth / Zigbee): 2-6 dBi
- 5.8 GHz: 3-8 dBi (high-gain easy to implement for high frequencies, low interference)
- UHF-RFID 902-928 MHz: 6-12 dBi
- GNSS Beidou / GPS: 20-28 dBi (active antenna)
5. Comparison: High Gain vs Low Gain
Low Gain (0-5 dBi)
Advantages: 360° omnidirectional coverage, uniform signal, few dead zones, suitable for indoor and complex environments Disadvantages: Short transmission distance
High Gain (≥ 6 dBi)
Advantages: Long transmission distance, strong signal, good anti-attenuation performance, ideal for open-air long-range outdoor deployment Disadvantages: Narrow beam and coverage angle, more signal dead zones, performance heavily affected by obstructions
6. General-Purpose Gain Selection Guidelines
- Indoor devices requiring signal from all directions → omnidirectional antenna with low gain of 2-5 dBi
- Long-range outdoor application, base stations, point-to-point links → high-gain antenna ≥ 6 dBi
- Space-constrained built-in device → low-gain internal antenna
- Longer reading distance and more tags for RFID → select higher-gain antenna
- GNSS positioning application → active high-gain antenna is mandatory
7.Antenna Gain Radiation-Pattern
| Frequency ID | Frequency (MHz) | Gain (dBi) | Efficiency (%) |
|---|---|---|---|
| 1 | 800.0 | 4.00 | 36.30 |
| 2 | 810.0 | 3.85 | 37.97 |
| 3 | 820.0 | 3.80 | 33.53 |
| 4 | 830.0 | 3.85 | 35.40 |
| 5 | 840.0 | 3.95 | 32.51 |
| 6 | 850.0 | 3.81 | 34.24 |
| 7 | 860.0 | 3.23 | 38.28 |
| 8 | 870.0 | 4.38 | 40.12 |
| 9 | 880.0 | 4.85 | 42.02 |
| 10 | 890.0 | 4.94 | 40.27 |
| 11 | 900.0 | 4.86 | 42.27 |
| 12 | 910.0 | 4.74 | 38.50 |
| 13 | 920.0 | 4.52 | 39.59 |
| 14 | 930.0 | 4.27 | 41.81 |
| 15 | 940.0 | 4.36 | 39.08 |
| 16 | 950.0 | 4.19 | 36.95 |
| 17 | 960.0 | 4.17 | 40.06 |
| 18 | 1700.0 | 3.99 | 38.79 |
| 19 | 1720.0 | 3.79 | 38.83 |
| 20 | 1740.0 | 3.91 | 37.67 |
| 21 | 1760.0 | 3.79 | 36.57 |
| 22 | 1780.0 | 4.71 | 37.82 |
| 23 | 1800.0 | 4.46 | 35.82 |
| 24 | 1820.0 | 4.26 | 38.05 |
| 25 | 1840.0 | 4.93 | 41.14 |
| 26 | 1860.0 | 4.87 | 42.81 |
| 27 | 1880.0 | 4.84 | 38.98 |
| 28 | 1900.0 | 4.84 | 40.04 |
| 29 | 1920.0 | 4.49 | 43.44 |
| 30 | 1940.0 | 4.21 | 43.92 |
| 31 | 1960.0 | 4.02 | 43.51 |
| 32 | 1980.0 | 4.16 | 44.47 |
| 33 | 2000.0 | 4.08 | 39.78 |
| 34 | 2020.0 | 4.19 | 39.41 |
| 35 | 2040.0 | 3.95 | 36.49 |
| 36 | 2060.0 | 4.05 | 35.80 |
| 37 | 2080.0 | 3.99 | 36.32 |
| 38 | 2100.0 | 4.60 | 39.64 |
| 39 | 2120.0 | 4.29 | 42.33 |
| 40 | 2140.0 | 3.75 | 39.33 |
| 41 | 2160.0 | 3.12 | 38.19 |
| 42 | 2180.0 | 3.40 | 36.21 |
| 43 | 2200.0 | 3.56 | 37.94 |
| 44 | 2220.0 | 3.27 | 36.84 |
| 45 | 2240.0 | 4.02 | 36.54 |
| 46 | 2260.0 | 4.29 | 39.87 |
| 47 | 2280.0 | 3.75 | 39.35 |
| 48 | 2300.0 | 4.12 | 42.87 |
| 49 | 2320.0 | 3.40 | 39.75 |
| 50 | 2340.0 | 4.96 | 40.45 |
| 51 | 2360.0 | 3.68 | 35.89 |
| 52 | 2380.0 | 4.01 | 36.87 |
| 53 | 2400.0 | 3.47 | 41.77 |
| 54 | 2420.0 | 3.60 | 36.47 |
| 55 | 2440.0 | 3.89 | 40.33 |
| 56 | 2460.0 | 3.75 | 42.87 |
| 57 | 2480.0 | 4.12 | 38.18 |
| 58 | 2500.0 | 3.40 | 38.75 |
| 59 | 2520.0 | 3.96 | 36.98 |
| 60 | 2540.0 | 3.27 | 36.41 |
| 61 | 2560.0 | 4.20 | 39.90 |
| 62 | 2580.0 | 4.90 | 39.80 |
| 63 | 2600.0 | 3.96 | 37.54 |
| 64 | 2620.0 | 3.43 | 36.18 |
| 65 | 2640.0 | 4.01 | 36.80 |
| 66 | 2660.0 | 3.81 | 36.91 |
| 67 | 2680.0 | 3.62 | 37.35 |
| 68 | 2700.0 | 4.21 | 35.21 |