Development History of GNSS High Precision Antennas

With the continuous development and improvement of satellite positioning technology, high-precision positioning technology has been applied to all walks of life in modern life. For example, in surveying and mapping, precision agriculture, drones, unmanned driving and other fields, high-precision positioning technology can be seen everywhere. In particular, with the completion of the networking of the new generation of Beidou satellite navigation system and the advent of the 5G era, the continuous development of Beidou + 5G is expected to promote the application of high-precision positioning technology in airport dispatching, robot inspection, vehicle monitoring, logistics management and other fields. The realization of high-precision positioning technology is inseparable from the support of high-precision antennas, high-precision algorithms and high-precision boards. This article mainly introduces the development and application of high-precision antennas and the current status of technology.

1. Development and application of GNSS high-precision antennas

1.1 Introduction to high-precision antennas

In the GNSS field, high-precision antennas are a type of antenna that has special requirements for the stability of the antenna phase center. They are usually used in conjunction with high-precision boards to achieve centimeter-level or millimeter-level high-precision positioning. In the design of high-precision antennas, there are usually special requirements for the following antenna indicators: antenna beam width, low elevation gain, non-circularity, roll-off coefficient, front-to-back ratio, anti-multipath capability, etc. These indicators will directly or indirectly affect the stability of the antenna phase center, and thus affect the positioning accuracy.

1.2 Application and classification of high-precision antennas

High-precision GNSS antennas were initially used in the field of surveying and mapping, and were used to achieve static millimeter-level positioning accuracy in engineering layout, topographic mapping, and various control measurements. With the increasing maturity of high-precision positioning technology, high-precision antennas are gradually being used in more and more fields, including continuously operating reference stations, deformation monitoring, earthquake monitoring, surveying and mapping, drones, precision agriculture, autonomous driving, driving tests and training, engineering machinery and other industrial fields. The requirements for antenna indicators in different applications are also significantly different.

1.2.1 CORS system, deformation monitoring, earthquake monitoring - reference station antenna

When high-precision antennas are used in continuously operating reference stations, accurate position information is obtained through long-term observations, and the observation data is transmitted to the control center in real time through the data communication system. The control center calculates the error correction parameters in the area and then sends the error information to the mobile station (user end) through the ground-based augmentation system, wide-area augmentation system, satellite-based augmentation system, etc., ultimately enabling the user to obtain accurate coordinate information [1].

In applications such as deformation monitoring and earthquake monitoring, it is necessary to accurately monitor the deformation and detect tiny deformations to predict the occurrence of natural disasters.

Therefore, in the design of high-precision antennas in applications such as continuously operating reference stations, deformation monitoring, and earthquake monitoring, the first thing that must be considered is its excellent phase center stability and anti-multipath interference capabilities, so that accurate position information can be provided in real time for various enhancement systems. In addition, in order to provide as many satellite correction parameters as possible, the antenna must receive as many satellites as possible, and the four-system full-band has become a standard configuration. In such applications, a reference station antenna (base station antenna) covering the four-system full-band is usually used as the observation antenna of the system.

1.2.2 Surveying and Mapping - Built-in Surveying Antenna

In the field of surveying and mapping, it is necessary to design a built-in measurement antenna that is easy to integrate. The antenna is usually built into the top of the RTK receiver to achieve real-time high-precision positioning in the field of surveying and mapping.

The main considerations in the design of built-in measurement antennas include frequency band coverage, beam coverage, phase center stability, antenna size, etc. In particular, with the popularization of network RTK applications, all-network built-in measurement antennas integrating 4G, Bluetooth, and WiFi have gradually occupied a major market share. Since their launch in 2016, they have been favored by the majority of RTK receiver manufacturers and have been widely used and promoted.

1.2.3 Driving test, driving training, unmanned driving - external measurement antenna

The traditional driving test system has many drawbacks, such as high investment cost, high operation and maintenance cost, great environmental impact, low accuracy, etc. After the high-precision antenna is applied to the driving test system, the driving test system is transformed from manual judgment to intelligent judgment with high judgment accuracy, which greatly reduces the manpower and material costs of the driving test.

In recent years, unmanned driving systems have developed rapidly. In unmanned driving, the positioning technology of RTK high-precision positioning and inertial navigation combined positioning is usually used, which can achieve very high positioning accuracy in most environments.

In driving tests, driving training, unmanned driving and other systems, external measurement antennas are often used. The antenna is required to have multi-system and multi-frequency working bands, be able to achieve higher positioning accuracy, have a certain degree of suppression ability for multipath signals, and have good environmental adaptability, and be able to be used for a long time in outdoor environments without failure.

1.2.4 UAV-High Precision UAV Antenna

In recent years, the UAV industry has developed rapidly. UAVs have been widely used in agricultural plant protection, surveying and mapping, power line inspection and other scenarios. In such scenarios, only high-precision antennas can ensure the accuracy, efficiency and safety of various operations. Due to the characteristics of UAVs such as high speed, light load and short endurance, the design of UAV high-precision antennas mainly focuses on factors such as weight, size and power consumption, and realizes the widest possible design while ensuring weight and size.

2. Current status of GNSS antenna technology at home and abroad

2.1 Current status of foreign high-precision antenna technology

Foreign countries started research on high-precision antennas earlier, and have also developed a series of high-precision antenna products with good performance, such as NoVatel's GNSS 750 series choke antennas, Trimble's Zepryr series antennas, Leica AR25 antennas, etc., many of which have antenna forms with great innovative significance. Therefore, for a long time in the past, my country's high-precision antenna market has been monopolized by foreign products. However, in the past decade, with the rise of a large number of domestic manufacturers, foreign GNSS high-precision antennas have basically no advantages in performance, and domestic high-precision manufacturers have begun to expand their markets abroad.

In addition, some new GNSS antenna manufacturers have developed abroad in recent years, such as Maxtena, Tallysman, etc. Their products are mainly small GNSS antennas for drones, vehicle-mounted systems, etc. The antenna form is usually a high dielectric constant microstrip antenna or a four-arm spiral antenna. Foreign manufacturers no longer have an advantage in the design technology of such antennas, and domestic and foreign products are entering a period of homogeneous competition.

2.2 Current status of domestic high-precision antenna technology

The productization of high-precision antennas in China started late but has developed rapidly. In the past decade, a number of domestic high-precision antenna manufacturers have begun to grow and develop, such as Huaxin Antenna, Zhonghaida, Dingyao, and Jiali Electronics, and have developed a series of high-precision antenna products with independent intellectual property rights.

For example, in the field of base station antennas and built-in measurement antennas, Huaxin's 3D choke antennas, all-network combination antennas, etc., not only have performance that reaches the international leading level, but also have high product reliability, long service life, and extremely low failure rate, which can meet the needs of various environmental applications.

In the automotive, drone and other industries, the design technology of external measurement antennas and four-arm helical antennas has become relatively mature, and has been widely used in driving test systems, unmanned driving, drones and other industry applications, achieving good economic and social benefits.

3. Current status and prospects of GNSS antenna market

In 2018, the total output value of my country's satellite navigation and location services industry reached RMB 301.6 billion, an increase of 18.3% over 2017[2]. It is expected to reach RMB 400 billion in 2020. In 2019, the total output value of the global satellite navigation market was 150 billion euros, and the number of GNSS terminal users reached 6.4 billion. Against the backdrop of the global economic downturn, the GNSS industry is one of the few industries that has bucked the trend. The European Global Navigation Satellite System Agency predicts that in the next decade, the total output value of the global satellite navigation market will double to more than 300 billion euros, and the number of GNSS terminals will increase to 9.5 billion.

In the global satellite navigation market, terminal equipment used in road traffic, drones and other fields is the fastest growing market segment in the next ten years: intelligent and unmanned vehicles are the main development direction of future road vehicles, and cars with autonomous driving capabilities must be equipped with GNSS high-precision antennas. Therefore, the autonomous driving market has a huge demand for GNSS antennas. With the continuous development of my country's agricultural modernization process, the use of drones equipped with high-precision positioning antennas, such as plant protection drones, will continue to grow.

4. Development trend of GNSS high-precision antenna

After years of development, various technologies of GNSS high-precision antennas have become relatively mature, but there are still many areas to be broken through:

1. Miniaturization: The miniaturization of electronic devices is an eternal development trend, especially in applications such as drones and handheld devices, where the demand for small-sized antennas is more urgent. However, antenna performance will decrease after antenna miniaturization. How to reduce the size of the antenna while ensuring comprehensive performance is an important research direction for high-precision antennas.

2. Anti-multipath technology: GNSS antenna anti-multipath technologies mainly include choke technology[3], artificial electromagnetic material technology[4][5], etc. However, they all have disadvantages such as large size, narrow bandwidth, and high cost, and cannot be universally designed. Therefore, it is necessary to study anti-multipath technology with miniaturization and broadband characteristics to meet various application requirements.

3. Multifunctionality: Nowadays, in addition to GNSS antennas, various devices also integrate more than one communication antenna. Different communication systems may cause various signal interferences to GNSS antennas, affecting normal satellite reception. Therefore, the GNSS antenna and the communication antenna are integrated through multifunctional integration. The interference between antennas is taken into consideration during the design, which can improve the electromagnetic compatibility characteristics and the performance of the whole device while increasing the integration degree.

5. Conclusion

This article briefly introduces GNSS high-precision antennas, focusing on their applications in different industries and the technical status of high-precision antennas at home and abroad, and summarizes their market conditions and development trends. With the popularization of 5G technology, Beidou + 5G technology will further promote the application of high-precision positioning technology in more and more fields, and high-precision positioning antennas will also usher in greater development space.

Source: China Satellite Navigation and Positioning Association

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