GNSS Antenna Types Explained: A Guide to Choosing the Right Antenna

What is a GNSS antenna? Selecting the right GNSS antenna type is the first step in building any positioning system. GNSS antennas are responsible for receiving signals from satellites, and the choice of different GNSS antennas types directly affects the accuracy, reliability, and cost of the system. This article will take an in-depth look at different GNSS antenna types to help you make the best choice for your application.

Table of Contents

What are GNSS antennas?

Frequency bands used by GNSS antennas

GNSS Antenna Types

Key Characteristics of GNSS Antennas and Their Impact on Performance

What are GNSS antennas?

GNSS stands for Global Navigation Satellite System, which refers to all satellite navigation systems, including global, regional, and enhanced systems. These systems include the US GPS, Russia’s Glonass, Europe’s Galileo, China’s BDS (BeiDou Navigation Satellite System), and related enhanced systems such as the US WAAS, Europe’s EGNOS, and Japan’s MSAS.

After capturing satellite signals, the GNSS antenna first removes unwanted noise and then amplifies the signal to a level that the receiver can process. The receiver uses timing data from these signals to calculate the distance to each satellite. By combining data from at least four satellites, the receiver can determine the user’s precise location using a method called trilateration.

Frequency bands used by GNSS antennas

GNSS antennas operate on specific frequency bands, which correspond to the signals transmitted by different satellite navigation systems (such as GPS (US), GLONASS (Russia), BDS (China), and Galileo (EU)).

Each satellite constellation also operates across multiple frequency bands.Each band enables GNSS antennas to receive a specific set of critical timing and positioning data from satellites, supporting a wide range of applications from basic navigation to high-precision measurements.

Key GNSS frequency bands include:

GPS (Global Positioning System)

L1 frequency: 1575.42 MHz, used for both civilian and military applications.

L2 frequency: 1227.6 MHz, primarily used for military applications but also provides civilian signals.

L5 frequency: 1176.45 MHz, used for civilian aviation and other safety-critical applications.

GLONASS (Russian Global Navigation Satellite System)

L1 frequency: 1602 MHz, using FDMA (Frequency Division Multiple Access) technology.

L2 frequency: 1246 MHz, also using FDMA technology.

L3 frequency: 1207.14 MHz, used for military signals.

Galileo (European Global Navigation Satellite System)

E1 frequency: 1575.42 MHz, the same as GPS’s L1 frequency, used for civilian purposes.

E5a frequency: 1176.45 MHz, identical to GPS’s L5 frequency, used for civil aviation.

E5b frequency: 1207.14 MHz, used for security applications.

E6 frequency: 1278.75 MHz, used for future civil and commercial services.

BDS (China's Beidou Satellite Navigation System)

B1 frequency: 1561.098 MHz, similar to GPS L1 and Galileo E1 frequencies.

B2 frequency: 1207.14 MHz, same as Galileo E5b frequency.

B3 frequency: 1268.52 MHz, used for civilian purposes.

There are also other frequencies such as E5 and E6.

Some may ask, does frequency overlap have any impact?

Different GNSS systems maintain compatibility and interoperability by sharing central frequencies and overlapping spectrum, enabling interoperability. This reduces the burden on receivers to provide reference frequency signals for different central frequencies, thereby lowering the power consumption, cost, and weight of multi-system GNSS receivers.

Therefore, multiple GNSS systems can be used simultaneously, especially dual-frequency or tri-frequency receivers, which enhance positioning accuracy and reliability, reduce sensitivity to signal errors, and improve interference resistance, making GNSS antennas versatile in various harsh environments.

This is particularly useful in environments where satellite signals may be weak or obstructed.

GNSS Antenna Types

There are two main GNSS antenna types: active antennas and passive antennas.We will also discuss these two GNSS antenna types based on their characteristics.

Active GNSS Antennas

Active GNSS antennas are equipped with integrated low-noise amplifiers (LNAs) that amplify weak satellite signals before they reach the receiver.

This amplification is critical in environments where satellite signals may be weak or obstructed, such as urban canyons, inside vehicles, or in high-precision applications like surveying. By improving signal quality, active antennas enhance reliability and accuracy, making them suitable for applications requiring robust performance in challenging conditions.

These antennas can also compensate for signal loss caused by long cable transmission, ensuring the receiver receives a strong and clear signal. As a result, active GNSS antennas are typically used in fixed installations, high-precision applications, and scenarios where environmental factors may interfere with satellite signals.

Passive GNSS Antennas

In contrast, passive GNSS antennas do not include any amplification functionality; they simply deliver satellite signals directly to the receiver. This design relies on the receiver’s inherent processing capabilities to handle the input signals.

Passive antennas are best suited for environments with strong satellite reception, such as open fields or rural areas with minimal interference. They are simple and require no electronic components, enabling a lightweight and compact form factor, making them an ideal choice for handheld devices and applications prioritizing low power consumption.

While passive GNSS antennas can sometimes be paired with external low-noise amplifiers to enhance signals when needed, they typically perform best under conditions where satellite signals are strong and stable, enabling efficient operation without adding the complexity of active components.

The decisive factor for GNSS antennas is their operating frequency range. However, certain GNSS antenna types are typically used for GNSS applications due to their specific characteristics. We discuss five of them below:

Patch Antennas

Patch antennas are compact, flat, rectangular, or circular antennas.
They are directional antennas that typically support RHCP (right-hand circular polarization) to match the polarization of GNSS satellite signals, thereby enhancing reception performance.However, if not installed correctly, they are often susceptible to multipath interference.
Patch antennas rely on a ground plane to reflect signals, making them suitable for both fixed and portable devices.They are ideal for fixed installations such as vehicle navigation, drones, and fixed sensors.

Helical Antennas

Helical antennas use helical coils to enable omnidirectional reception even without a large ground plane, making them highly versatile.
They provide high gain through circular polarization and help suppress multipath signals. They perform well in challenging environments but may be larger than patch antennas.
Helical antennas are suitable for low-profile applications such as handheld devices, portable GNSS devices, and wearable devices.

Choke Ring Antennas

Choke ring antennas feature a ring around the central radiating element, which helps mitigate multipath interference by suppressing ground reflections.
These antennas offer high multipath suppression, stable phase center, and robust performance, making them particularly suitable for professional high-precision applications.
They are typically used in high-precision applications, including geodesy, meteorology, and static GNSS stations.

Chip antennas

Chip antennas are miniaturized, low-profile antennas designed to fit into constrained form factors.
Chip antennas have low gain and are more susceptible to interference, making them primarily suitable for devices where size is the primary constraint.
These antennas are primarily used in small, lightweight devices such as wearable devices and IoT sensors. They are best suited for applications where size and cost take precedence over high-precision signal accuracy.

Multi-element and Cross-Dipole Arrays

Multi-element arrays and cross-dipole antennas provide enhanced directional capability and stronger signal suppression for unwanted polarization.
They offer high gain, excellent multipath suppression, and support for multiple GNSS frequency bands.
These antennas are used in advanced applications requiring multi-frequency or high-precision GNSS, such as drones or automotive applications with real-time kinematic (RTK) functionality.

Each of these antennas has unique advantages, making them suitable for a wide range of GNSS applications, from handheld devices to high-precision measurement instruments.

Key Characteristics of GNSS Antenna and Their Impact on Performance

Several key characteristics of GNSS antennas significantly influence their functionality and overall performance.

Frequency Coverage Range

GNSS antennas must cover the frequency ranges of multiple satellite navigation systems, such as the L1, L2, and L5 bands of GPS, the L1 and L2 bands of GLONASS, and the corresponding bands of systems like Beidou and Galileo. These bands span the frequency ranges of 1559–1606 MHz (L1 band) and 1166–1187 MHz (L5 band). The coverage of the operating frequency range directly affects the antenna’s ability to receive signals.

Gain

The gain of a GNSS antenna indicates its ability to amplify signals in a specific direction. Higher gain enhances the antenna’s signal reception capability, improving positioning accuracy and stability. For example, some GNSS antennas can achieve a gain of up to 5 dBi.

Circular polarization

GNSS antennas must have circular polarization functionality. Antennas with circular polarization can receive signals from satellites regardless of their direction. This feature helps improve signal integrity and reduce the impact of multipath interference, which is critical in urban and densely populated environments.

Multipath Suppression

This attribute involves techniques to minimize the impact of reflected signals, which can distort received signals. Effective multipath suppression is critical for improving accuracy and reliability, especially in complex environments.

Axis Ratio

The axis ratio is a metric for evaluating an antenna’s circular polarization performance, describing its ability to receive signals in different directions. A lower axis ratio indicates better circular polarization performance and stronger suppression of cross-polarized signals, thereby providing higher accuracy.

Impact on Receiver Sensitivity

The design and characteristics of an antenna directly influence the sensitivity of a GNSS receiver. Antennas with high gain and low noise characteristics enhance receiver sensitivity, enabling better performance under challenging conditions.

Interference handling

The antenna’s ability to manage and mitigate interference from other electronic devices is critical for maintaining signal quality. Robust interference handling capabilities ensure that GNSS systems can operate reliably in various environments. Understanding these characteristics is essential for selecting the appropriate GNSS antenna for specific applications, ensuring optimal performance and accuracy. GNSS plays a critical role in modern positioning and navigation systems, impacting a wide range of applications from precision agriculture to autonomous vehicles.