Design And Implementation Of ELoran Omnidirectional H-field Antenna

With the wide application of high-precision satellite navigation and timing,the fields of surveying and mapping,military,and transportation all rely heavily on satellite-based systems.However,due to the low signal transmission power of the satellite-based system,the signal is fragile and susceptible to interference,and the enhanced Loran(e Loran)system,which is more secure and reliable in anti-jamming,has become the main method for backup and enhancement of satellite navigation timing.The receiving antenna is an important part of the Loran receiver,mainly including E-field antenna and H-field antenna.Compared with E-field antennas,H-field antennas have the advantages of no grounding requirement,insensitivity to deposition electrostatic interference,easy miniaturization and integration with GNSS,etc.,and Hfield antennas have become the trend of Roland receivers.Based on this,this paper conducts related research on the e Loran omnidirectional H-field antenna.The main contents are as follows:(1)Analyze the resonant circuit of the H-field antenna,determine its electrical parameters,and select an appropriate magnetic material as the magnetic core to provide a basis for the design and implementation of the H-field antenna.Starting from the receiving principle of the H-field antenna,the equivalent circuit of the H-field antenna and its resonant circuit are analyzed,and the inductance value of the H-field antenna is calculated according to the relevant formula of resonance;the magnetic material in the H-field antenna is discussed to select the magnetic core of the H-field antenna.(2)Design the array mode and coil specifications of the omnidirectional H-field antenna,and simulate the designed H-field antenna.The two common array formation methods are compared and analyzed,the design of the cross-shaped H-field antenna is selected,and the influence of the shape of the magnetic rod on the magnetic field and coil inductance is analyzed.On the basis of the design of the cross-shaped H-field antenna,the coil is designed,based on the determined inductance value,shape and permeability and other parameters,and according to the relevant formula and derivation,find the number of turns and the winding method suitable for it.The H-field antenna designed in this chapter is simulated and analyzed by FEKO,and the results show that the cross-shaped H-field antenna has omnidirectionality.(3)The power of the Loran signal received by the miniaturized H-field antenna is low.Design the active circuit part of the H-field antenna,and study its low-noise amplification and differential driving front-end technology to further process the signal.Based on the theoretical values calculated,a amplifier circuit module with dual common emitters is designed;and the designed circuit is simulated and analyzed by LT spice software to verify its voltage amplification and input and output impedance characteristics.The analysis results show that the voltage is amplified by 77 times;and a differential drive amplifier circuit is designed in the latter stage,which can drive and load the circuit and has a certain voltage amplifying effect;the overall circuit is simulated,analyzed and tested,and the results show that its total gain is 38 d B.(4)The fabricated active magnetic antenna was tested,and the performance of the e Loran omnidirectional magnetic antenna was verified by near-field and far-field tests.The actual measurement results show that the performance indicators of the H-field antenna are in line with expectations,and it can receive the e Loran signal of the transmitting station omnidirectionally.The flatness in the frequency range of 90-110 k Hz is ≤1.35 d B,and the 3d B bandwidth is between 32-38 kHz.