UA92 | Choke Ring Antenna

Powerful Satellite Tracking Capacity

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Access reliable and comprehensive data sources, encompassing all channels and signals such as GPS, BDS, GLONASS, GALILEO, IRNSS, QZSS, and SBAS for GNSS tracking.

High Gain ('5.5 dBi)

Benefit from robust GNSS satellite tracking capabilities, enhancing your measurement reliability due to the impressive antenna gain.

High Phase Center Accuracy

Experience sub-millimeter phase center accuracy with enhanced stability.

Rugged Design for Harsh Environments

Designed to last, the IP67 rating protects 95% against solid particles such as dust and sand, and it's proven to function for at least 30 minutes submerged in water between 15 cm to 1 m deep.

Exceptional Multipath Suppression Effect

Don’t be concerned about multipath interference thanks to its unique choke coil construction.

Multiple Applications

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The compact size and lightweight structure of the UA92 make it suitable for various applications, including mechanical control, deformation monitoring, and marine mapping.

1. Introduction

The accuracy of measurement systems like GNSS (Global Navigation Satellite Systems) hinges on their ability to operate reliably. This reliability can be assessed through analysis of measurement inaccuracies, which may manifest as systematic errors—consistent across measurements—or random varieties affecting individual readings. Manufacturers work diligently to curtail systematic inaccuracies during design phases, addressing factors like receiver clock errors effectively through compensation methodologies. However, most discrepancies observed in GNSS readings arise from random factors, warranting mathematical statistical approaches for their description.

Analyzing the performance of satellite systems underscores the significance of radio signal propagation conditions. These conditions are influenced by various phenomena such as obstructions from buildings or foliage, signals reflecting off different surfaces, and multipath wave propagation.

Obstructions like buildings block radio waves and reduce their energy levels. Reflected signals and multipath phenomena lead to radio wave fading, a frequent occurrence that can be alleviated through diverse frequency transmission in receivers, specialized antenna designs, or sophisticated data processing algorithms.

Modern GNSS receivers typically utilize at least dual transmission frequencies and come equipped with comprehensive signal processing capabilities. The evolution of antenna design has emerged as a primary strategy for mitigating reflection and multipath effects.

A diverse array of antennas are deployed in GNSS applications—from compact patch antennas for navigation purposes to intricate geodetic antennas used in specialized assignments. Choke ring antennas are notable among these; they are designed to dampen signals arriving at lower or negative elevation angles efficiently, employing coaxial rings or quarter-wave chokes of carefully selected depth, generally equating to one-quarter of the antenna’s operating frequency wavelength. A key benefit of such configurations includes the prevention of transverse electric current flow, effectively electrically isolating the active antenna component from surrounding structures. Additionally, these antennas offer heightened protection against jamming and interference from proximate radio devices. Still, their considerable weight, often resulting from metal (commonly steel) used in constructing the rings, can be a drawback.

Localized effects, like multipath, also originate from the vicinity around receiving antennas, contributing to errors in position fixes, predominantly through multipath signal propagation. The primary purpose of any antenna is to furnish clear, precise signals to a GNSS receiver, and integrated choke ring antennas—though commercially available—are often priced at a premium.

Notable studies, such as those by Leica on the AR25 choke ring antenna, report minimal standard deviations for localization scatter, signifying the antenna's high positioning repeatability. Ongoing research aims at the design of more compact and lighter antenna versions, often structured from deep concentric rings set on flat circular metal planes, while investigating diverse configurations, such as trapezoidal shapes.

Further explorations delve into the time and frequency-domain responses of various choke ring shielding setups. Such antennas promise effective application within low-cost GNSS receiver frameworks for static measurements, and research has also scrutinized smartphone integrations as GNSS antennas placed within choke ring configurations, revealing substantial enhancements in localization accuracy across X, Y, and Z coordinates. Comparative studies showcased choke ring antennas as proficient in establishing multipath error baselines compared to standard beacon antenna setups, particularly under forest canopies.

Nevertheless, it has been observed that standard GNSS signals within typical Central European forest stands paired with choke ring antennas yield precision exceeding a sub-meter level. The analysis of GNSS antenna altitudes on pseudorange multipath illustrates the choke ring antenna as the most effective in mitigating multipath reflections.

Choke ring antennas find practical applications in the positioning of Unmanned Ground Vehicles (UGVs). The challenges of localization with GNSS in UGV contexts have inspired considerable scholarly discourse. GNSS frequently operates as the reference positioning system of choice, necessitating prolonged and dependable GNSS signal functionality, especially under RTK mode to achieve the desired precision. However, this method encounters obstacles due to natural conditions impacting satellite visibility.

This article aims to outline the impact of cost-effective choke ring antennas on GNSS receiver positioning accuracy in RTK mode, particularly amidst potential multipath disturbances. The positioning inaccuracies of two antenna types—the choke ring and a dedicated GNSS antenna from the manufacturer—will be critically evaluated, assessing the feasibility of utilizing choke ring antennas in RTK measurements.

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