Study And Design Of Loran-C Magnetic Antenna

Loran-C system,one of most widely used ground-based navigation system,has often been employed in positioning,navigation and timing(PNT)field.The Loran-C receiver is a terminal device to carry out the Loran-C navigation.Its performance improvement is informative to the promotion and application of the whole system.Antennas play an important role in the Loran-C receiver,which the magnetic antenna becomes the mainstream of the Loran-C receiver antenna because of its compact volume,high sensitivity and broadband width.The high sensitivity,high signal-to-noise ratio and broadening bandwidth of the Loran-C magnetic antenna are focused in this thesis.The main contents of the work are as follows.(1)According to the theory of magnetic antenna,the best magnetic core applied to Loran-C signal frequency and bandwidth is picked up.The Mn-Zn ferrite is chosen as the core of the Loran-C magnetic antenna by comparing the curie temperature,magnetization characteristics and frequency application range of the magnetic materials.The loss of the magnetic core and the effective permeability of the cylindrical core are simulated and analyzed.It is finally determined that the effective permeability and length-to-diameter ratio range of the magnetic core of Loran-C magnetic antenna.(2)Field patterns of magnetic antennas with different structures are simulated.The results demonstrate that the field pattern of cross-loop magnetic antenna is greater single magnetic antenna.The parameters and performance of the magnetic antenna are studied.A series-connected multi-layer coils magnetic antenna is proposed,which improves the sensitivity of the magnetic antenna by 2?3 dB,the signal-to-noise ratio by 2?6dB.A magnetic negative feedback magnetic antenna is proposed,which makes the bandwidth of the magnetic antenna expand to 90?110 kHz,without reducing the inductive voltage.The linear range of the phase of the Loran-C magnetic antenna at the resonant frequency is remarkably increased.(3)The hardware circuit of signal conditioning circuit applied to Loran-C magnetic antenna are designed.The effect of gain resistances on output noise of low noise amplifier circuit are simulated.To reduce output noise,two-stage low-noise amplifier circuits with gain of 40 dB and 20 dB are designed.The system characteristic curves of band-pass filter circuit with Q value of 5,8 and 10 are simulated.The band-pass filter circuit with Q value of 5 and pass-frequency band width of 90?110 kHz is designed according to the simulated results.The signal conditioning circuit is debugged and realized.(4)Loran-C magnetic antenna with a volume of 200×200×100mm3 is manufactured and tuned.The Loran-C magnetic antenna is experimented in far field.The received Loran-C signals have clear pulse groups and high signal integrity.The maximum output voltage of the signal is 1.96V,the sensitivity is increased by 2.32dB,the SNR is 29.76 dB,the SNR is increased by 4.26dB,the bandwidth is 90?110kHz,which meets the bandwidth of Loran-C signal.