The global satellite navigation system has the characteristics of full-time, all-weather, high-precision, continuous real-time navigation, positioning and timing, so it plays an increasingly important role in economic development, scientific research, disaster prevention and control and military fields. Major powers are racing to develop independent satellite navigation systems. At present, the global satellite navigation systems include GPS in the United States, GLONASS in Russia, BEIDOU in China, and GALILEO in Europe. In addition to the above-mentioned four global systems and their augmentation systems (WAAS in the United States, EGNOS in Europe, and SDCM in Russia), countries such as Japan and India are also building their own regional systems and augmentation systems (QZSS and MASA in Japan, IRNSS) as well as commercial satellites and STARlink.
The increasingly widespread application of satellite navigation systems will surely play an important role in economic development and informatization construction, and will greatly enhance the comprehensive strength of the corresponding countries.
The phase measurement satellite navigation receiver has high positioning accuracy and is widely used in geographic information mapping, channel surveying and information management, resource exploration, bridge and tunnel construction and deformation monitoring, crustal terrain and landslide monitoring, dock container operations and other civil applications. In the project, there is a huge market demand. At present, the existing handheld phase measurement satellite navigation receivers mostly use single-constellation, multi-constellation, single-frequency, or general multi-constellation dual-frequency antennas, which is not a high-precision satellite navigation antenna for dual-frequency multi-constellation joint navigation in the true sense.
According to the positioning principle and the characteristics of satellite signals, the full use of GPS, Beidou and integrated navigation can greatly increase the number of satellites observed, which will ensure that the receiver has more than one navigation satellite with a large elevation angle anywhere. It is beneficial to reduce the multipath error, improve the positioning accuracy, shorten the positioning time, and improve the reliability of the observation structure, especially in the case of serious occlusion of signals in urban canyons and deep forests. The adoption of dual-frequency navigation can compensate for ionospheric delay and improve positioning measurement accuracy. In addition, it must have the characteristics of high phase center stability, good multipath suppression, and large axial ratio bandwidth of right-handed circular polarization.
It can be seen that the antenna used for high-precision satellite navigation has a high scientific and technological content. The characteristics of dual-band broadband and the ability to cover multiple satellite navigation constellations at the same time are particularly important, and it is also the difficulty in its design. The dual-frequency broadband navigation antenna will be of great significance to promote the development of high-precision satellite navigation terminal equipment.
Advantages: It has the characteristics of high-precision measurement antenna, has low elevation angle, high gain, stable phase center, and is suitable for use in reference stations with choke coils.
Disadvantages: bulky, which limits its application in handheld receivers.
Advantages: It has the advantages of small shape, low cost, easy conformality, easy processing, and can be easily integrated with the feeding network and active amplifier circuit. It is also easy to obtain the circular polarization mode by selecting a specific patch shape and feeding method.
Disadvantages: The microstrip patch antenna has the disadvantage of narrow operating bandwidth, and the typical radiation bandwidth is only a few percent.
By reducing the dielectric constant of the dielectric substrate of the microstrip antenna or increasing the thickness of the substrate, the working bandwidth can be widened, but the widening amount is very limited and the volume increases with the increase of the substrate thickness of the antenna. If a rectangular microstrip patch is opened or multiple short slits parallel to the edge can reduce the size of the antenna, the use of coupled feeding, multi-point feeding, center short-circuit nails or patch corner cutting and other improvement measures can help to properly improve the performance of the patch antenna and greatly improve the radiation bandwidth and axial ratio bandwidth of the antenna.
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