# Research on the Positioning Performance of GNSS with a Low-Cost Choke Ring Antenna
## 1 Introduction
The subject of research is also antennas of a different shape, such as trapezoidal [19]. The time and frequency-domain responses of various choke ring shielding structures are also investigated [20; 21; 22]. Choke ring antennas can also be used for low-cost GNSS receivers in static measurements [23]. Positioning accuracy tests were also the subject of research in the context of using smartphones as GNSS antennas placed in a choke ring [24]. In the discussed research, it was shown that the use of a choke ring type cover improves the accuracy of localization in the X, Y, and Z coordinate systems. A choke ring antenna can also be an effective tool for establishing a baseline of possible multipath error as compared to a standard beacon antenna configuration under forest canopies [25]. However, other studies have shown that the precision of GNSS signals in static measurements within typical forest stands for Central Europe with the use of a choke ring antenna is greater than the sub-meter level [26]. The influence of GNSS antenna height on pseudorange multipath was analyzed in the article [27]. Three antennas in total were analyzed: a choke ring antenna, a geodetic microstrip patch, and an antenna used for Real Time Kinematic (RTK) measurements. Multipath signals reflected from the ground were mitigated most effectively by the choke ring antenna [27]. In conclusion, no works related to the performance tests of a dedicated GNSS antenna in a version without/with a low-cost choke ring cover have been found. One of the possible uses of choke ring antennas is the positioning of Unmanned Ground Vehicles (UGVs). Localization problems, including the application of GNSS in UGVs, are the subject of many scientific articles [28; 29; 30]. GNSS is used mostly as a system for determining a reference position with high accuracy. In most cases, it is important to ensure the long-term and stable operation of the GNSS signals. Mentioned high accuracy of positioning is also required, which is most often provided by the RTK mode. It is especially critical when GNSS is the only UGV location system. This technology is often used in the field, but it has several limitations related to the need for an open horizon or satellite signal interference. In a lot of cases, the use of GNSS is simply impossible, e.g., due to environmental factors (independent of humans), while the goal is to protect GNSS antennas against the phenomenon of signal multipath or simply against external interference under good visibility. The solution in such cases could be choke ring antennas; however, their use is associated with reduced visibility of the horizon, which may affect the accuracy of the system. The positioning accuracy of GNSS is the subject of scientific articles [31; 32; 33; 34; 35]. In the case of stationary tests, long-term measurements are most often used to eliminate the occurrence of random errors. In conclusion, no works related to the positioning accuracy of the GNSS with the choke ring antennas working in RTK mode on UGVs have been found. Accordingly, the purpose of the article is to determine the influence of the low-cost choke ring antenna on the GNSS receiver positioning accuracy working in RTK mode in the environment with possible multipath effects. For comparison, the article specifies positioning errors for two types of antennas: the aforementioned choke ring antenna and the dedicated GNSS antenna supplied by the manufacturer. In this way, the possibility of using the choke ring antenna in RTK measurements was also analyzed. The positive results of the experiment will determine the possibility of using the designed antenna on UGVs.