To maximize performance, GNSS antennas have been optimized to receive signals from multiple satellite systems with different frequencies and modulation schemes. It usually contains radiation elements to capture signals, which are then guided and shaped through feeders and ground layers.

The placement and orientation of the antenna are of vital importance. It must avoid obstacles such as trees and buildings; otherwise, it may cause signal reflection and multipath interference, affecting performance.

The common types of GNSS antennas are as follows:

• Patch antenna: Composed of metal conductive patches on a dielectric substrate, with a ground layer at the bottom. It is compact, thin, performs well and is cost-effective, making it suitable for handheld and wearable devices.
• Helical antenna: It is in the shape of a helical coil, featuring high gain and circular polarization characteristics. It can reduce the influence of multipath interference and receive signals better than patch antennas. It is compact and lightweight, requiring no ground layer, and is used in unmanned aerial vehicles, unmanned ground vehicles, unmanned systems, high-precision navigation, military and security, smart agriculture, and handheld GNSS devices, etc.
• Choke ring antenna: Composed of concentric conductive cylinders surrounding the central antenna, it usually has a protective cover to withstand harsh weather when used outdoors. It has excellent phase center stability and polarization purity, can suppress radiation below the horizon and multipath, and is used in satellite navigation, surveying and geological surveying.

GNSS antennas receive positioning and timing data signals from satellite constellations and are applied in multiple fields such as intelligent transportation, navigation, measurement, and infrastructure inspection. They can receive signals from satellite systems such as the US GPS, the EU Galileo, China's Beidou, and Russia's GLONASS. Its working principle is to convert satellite electromagnetic waves into electrical signals, filter out noise and amplify it to a level that the receiver can handle. The receiver uses timed data to calculate the distance to the satellite and determines the user's precise position (latitude, longitude, altitude) by combining the information of at least four satellites with the trilateration method.

GNSS antennas are classified into active and passive types based on whether an external power supply is required.

• Active GNSS antenna: It requires an external power supply. The built-in electronic device can amplify the signal to overcome signal loss caused by cable attenuation or long cable operation.
• Passive GNSS antennas: Simpler and cheaper, without built-in electronic devices, they require GNSS receivers to amplify signals. They may have higher signal loss due to cable attenuation or being too long. They are used in cost-prioritized applications such as consumer GPS devices.

To ensure positioning accuracy and reliability, GNSS antennas collect signals from multiple frequency bands:

L1 band (~1575.42 MHz) : A major civilian frequency, compatible with most GNSS receivers, and used by GPS, Galileo, and Beidou.

L2 band (~1227.6 MHz) : Mainly used in GPS military applications, when combined with L1, it can enhance the signal robustness of some civilian applications in dual-frequency systems.

L5 band (~1176.45 MHz) : "Life Safety" band, designed for high-reliability applications such as aviation, with strong anti-interference ability.

E6 band (1260-1300 MHz) and B3 band: They help professional applications achieve multi-frequency accuracy and enhanced integrity, and are respectively used by Galileo (E6) and Beidou (B3).

Other frequency bands: including L6 of GPS, E1, E6, E5 of Galileo, G1, G2, G3 of GLONASS, B1, B2, B3 of Beidou, etc.

In terms of design, GNSS antennas have multiple performance requirements:

1. Impedance: 50Ω is the standard configuration for antennas and cables.
2. VSWR (Voltage Standing Wave Ratio) : It is usually less than 3:1 to ensure good impedance matching.
3. Return loss (RL) : A return loss greater than 6.0 dB indicates a low reflected power.
4. Efficiency: Over 50% can effectively receive signals.
5. LNA (Low Noise Amplifier) gain: The gain of an integrated or external LNA should typically be greater than 15 dB.
6. LNA noise figure (NF) : Ideally less than 1.0 dB to reduce the addition of noise.
7. Antenna gain: It measures the degree to which terminal signals are converted into radiated power. The higher the gain, the better the reception effect is usually.
8. Axial ratio: It measures the purity of circular polarization. The axial ratio of perfect circular polarization is 0 dB.
9. Phase center offset/phase center variation (PCO and PCV) : It indicates the precise electrical receiving point on the antenna and its variation with the signal Angle, which is important for high-precision applications.
10. Group delay: Instrument errors in the receiver and antenna can affect signal timing.

Relevant standards for GNSS Antennas Cable:

ETSI EN 303 413: European standard and CE RED requirements ensure that GNSS functionality meets the minimum interference tolerance, especially interference from adjacent frequency bands.

RTCA/DO-228 and RTCA DO-373A: Define the minimum operational performance standards (MOPS) for airborne GNSS antenna equipment, ensuring reliability and addressing spoofing risks for aviation applications.

Connection: A variety of connector types are used in combination with GNSS antennas, including: TNC, N, SMA, BNC, U.F.L and MMCX.

Type:

Microstrip antennas (commonly found in small devices, with small size and low cost);

Helical antenna (with high gain, suitable for complex environments);

Array antenna (multi-unit combination, enhancing anti-interference and directional reception capabilities).

Market and Application

Consumer-grade devices such as in-car navigation systems, drones, and smart phones;

Professional fields such as surveying and mapping, geological exploration, and precision agriculture (requiring high-precision antennas);

Scenarios with extremely high reliability requirements, such as aerospace and maritime navigation.

Intelligent transportation, vehicle testing, autonomous driving, navigation, surveying and geographic information systems, geospatial mapping, bridge and infrastructure inspection, as well as time synchronization.

In conclusion, GNSS antennas serve as the "bridge" connecting satellites and receivers, and their performance directly affects the accuracy, stability and signal capture capability of positioning