Choke ring antenna

What is a Choke Ring Antenna?

A choke ring antenna is designed specifically for GNSS applications, featuring a central antenna element encircled by multiple concentric conductive rings. These antennas excel in rejecting multipath signals, which occur when satellite signals are reflected off obstacles such as buildings, topography, and water surfaces. Each groove in the choke ring antenna includes specialized filters that minimize multipath signals across both the L1 and L2 frequency bands, all within a single antenna structure.

The ability to accurately measure the distance from the transmitter to the receiver makes choke ring antennas ideal for applications like GPS surveying and geological measurements, particularly in forestry. By effectively reducing multipath interference, these antennas can significantly improve the precision of GPS data, potentially achieving centimeter-level accuracy when paired with high-quality mapping-grade GPS receivers.

Construction

Typically crafted from a single aluminum billet, choke ring antennas consist of several concentric rings, usually ranging from three to five, each of consistent depth surrounding a central ring that houses the antenna receiver. These choke rings are designed to be a quarter wavelength deep to create a high impedance surface, which minimizes surface wave propagation and prevents the excitation of unwanted modes. This careful construction results in a finely controlled radiation pattern that significantly reduces vulnerability to multipath effects.

The standard dimensions of a choke ring antenna are generally between 300-450 mm in diameter and 60 mm in depth, with a typical weight of approximately 7 kg. While these dimensions are effective for laboratory and survey applications, their physical size can hinder practical use in field studies, especially in dense forest environments. Additionally, choke rings are engineered to mitigate electromagnetic energy that is reflected from the Earth, enhancing signal quality and reliability.

To ensure durability, especially for outdoor applications, the entire apparatus is often housed within a protective cover.

Limitations

Despite their advanced design, choke ring antennas have inherent limitations, particularly concerning antenna gain at low elevation angles (below 20°). This deficiency can diminish signal strength, leading to reduced positional accuracy in scenarios where signals arrive from low angles.

If you seek to discover more about the MINI Choke ring antenna, reach out to us today to arrange an expert consultation!