Design And Direction Finding Algorithm Of Loran-C Miniaturized Magnetic Antenna

The Loran-C navigation system is a land-based medium to long range low-frequency radio navigation system widely used in fields such as positioning,navigation,and timing(PNT).Due to the advantages of strong anti-interference ability and stable signal quality of long wave signals,as well as the drawbacks of low signal transmission power and susceptibility to interference in the Global Navigation Satellite System(GNSS),the Loran-C navigation system has become the main backup and enhancement method for global navigation satellite systems,and has attracted the attention of navigation and time service institutions in various countries in recent years.Antennas are an important component of Loran-C receivers and the main factor affecting their performance.The research on high-performance,highly reliable,and miniaturized antennas is of great significance for improving the performance of Loran-C receivers.The Loran-C receiving antenna is mainly divided into two types:electric antenna and magnetic antenna.Compared to electric antenna,magnetic antenna has advantages such as small size,high sensitivity,strong anti-interference ability,and no need for grounding.It has wider applications and better adaptability,and is also easy to integrate with GNSS antenna design.Based on this,this article focuses on the design and direction finding algorithm of Loran-C miniaturized magnetic antenna.The main work of this article is as follows:(1)This article starts with the selection of magnetic core materials and coil winding methods,and optimizes the design of magnetic rods.Theoretical analysis combined with experimental results shows that using low loss and high permeability magnetic core materials can effectively reduce the size of the antenna;Under the same magnetic core material conditions,the magnetic antenna made of rectangular magnetic cores has better signal-to-noise ratio in receiving signals compared to the magnetic antenna made of cylindrical magnetic cores;For the winding method of the coil,compared to the single-layer coil,the double-layer coil only increases the received signal amplitude and does not significantly improve the signal-to-noise ratio.Based on the performance and ease of production of magnetic antennas,this article adopts a rectangular magnetic core and a single-layer coil structure to develop magnetic antennas.(2)A miniaturized and high signal-to-noise ratio omnidirectional magnetic antenna was designed by optimizing the layout of dual magnetic rods and antenna resonant circuit.The structure of orthogonal arrangement of two magnetic antennas achieves omnidirectional reception of the antenna;By optimizing the capacitance and matching impedance of the resonant circuit,the magnetic antenna can effectively receive signals in the 100kHz±20kHz frequency band while balancing the quality factor and bandwidth of the magnetic antenna;Adapt the received Roland signal to the receiver input through two-stage amplification.Finally,a volume of 110 × 110 × 10 mm3 active omnidirectional magnetic antenna can receive complete Roland signals with a signal-to-noise ratio of up to 20dB in far-field testing at a distance of over 90 kilometers.(3)A magnetic antenna direction finding algorithm based on coupling parameter compensation is proposed.Due to the structural and layout issues of the magnetic antenna itself,there may be mutual coupling between the two magnetic antennas.By fitting a set of coupling parameters through multi angle measurement,the influence of antenna asymmetry and mutual coupling on the measurement results is solved,and the direction finding results are corrected to achieve phase compensation for the signal.The test results show that the magnetic antenna pointing error obtained through the coupling parameter compensation direction finding algorithm is within 10 ° of the actual pointing error,which can provide more accurate directional information.