Research On Weak Signals Measurement Based On Phase Lock Loop

The measurement of satellite weak signals based on a tracking loop with third-order phase lock loop is studied under the background of two-dimension course correction.During the rotation of the projectile,the energy of the satellite signal received by the single-patch antenna fluctuates and it is modulated by the rotation angle of the projectile.Therefore,we can utilizing a single-patch antenna mounted on the projectile to complete the rotation angle measurement.With the roll of the projectile,receiving of the satellite signal is quite frequent,while the traditional signal detection methods has higher computational complexity,resulting in poor real-time performance which cannot meet the application requirements.Since the satellite signal reaching the ground is weak and the signal strength is much lower than the base noise,we are faced with a problem that the useful signal extraction is difficult.Therefore,this paper mainly studies the following two aspects:first,the useful signal extraction when the directional antenna receives weak satellite signal;second,the problem of improving the real-time performance in the weak signal detection.In this paper,we firstly analyze the characteristics of directional antenna receiving satellite signals under rotating condition and compare various weak signal detection methods.The basic principle of phase-locked tracking is studied,and the scheme of detecting weak signals by phase-lock loop is proposed.Third-order phase lock loop is designed and the tracking performance of the phase lock loop under different parameters is analyzed in detail.The design principles of the phase lock loop parameters are obtained.The third-order phase lock loop design is verified through simulation.Aiming at the design of the third-order phase lock loop,we carry out a half-physical simulation and a real scene experiment of rotary table.The experimental results show that the rotation speed that we get is normal,which verifies the feasibility of the proposed weak signal detection method based on the principle of phase-locked tracking.