Study On Guidance Technique Of Phased Array Radar Seeker On Platform

For the risk of the positive feedback characteristic of the strapdown phased array radar seeker isolation leading to the serious instability of guidance loop, the thought of platform-based phased array radar seeker is put proposed. By studying on structure design, performance analysis, error sources and guidance performance impact, the feasibility analysis of the plan and technology which extract the line of sight of the platform-based phased array radar seeker is carried out. The method can avoid the effect of the whole strapdown phased array radar seeker positive feedback isolation by obtaining isolation performance of projectile swinging interference and decreasing amplitude seeker disturbance rejection rate, but at the expense of increasing the frame structure. Research results show that the extraction principle of line of sight, the level of error sources influence and the application on roll projectile can provide the theory reference for the phased array radar for to-air missile engineering application.The discussion on the principle of whole strapdown phased array radar seeker tracking the line of sight, the mechanism of traditional platform seeker extracting the line of sight, and the selection of the framework build a preliminary design scheme of the platform-based phased array radar seeker. The analysis on the influence due to load, frame angle, antenna array surface area and weapon system combat closed-loop are given. Using the frame to replace the original body of the whole strapdown phased array radar seeker, the detailed design of the platform-based phased array radar seeker model is completed. The design results show that the scheme is feasible. The platform-based phased array radar seeker has both the phased array radar’s advantage of rapid scanning and tracking and the platform-based seeker’s ’s advantage of isolation projectile swinging.The four scheme of seeker tracking the line of sight and guidance signal extraction are built according to the difference between the phased array radar’s and platform framework’s tracking loop and the points of extracting the angular velocity of the line of sight. The Reasonable parameters are introduced through model simplification and researching the influence on the step response of angular velocity of the line of sight, the track of different frequency band of the guidance signal and the effect of rapidity for the performance of the guidance. The most rational scheme of seeker signal output is concluded. Taking advantage of ability that the platform-based phased array radar seeker can track the fast target, the application technology on the two-box platform-based phased array seeker rotary projectile is studied. The change rule of the beam angle, the frame angle and the single pulse measuring angle in the different rotary frequency is analyzed. Results show that the seeker can well track the guidance high frequency signal, and can be applied to terminal guidance of the roll missile with high frequency.By introducing different error source models, Effects of single pulse measuring angle error, phase shift caliber error, calibration error of radar beam, angular rate gyro dynamics, radome error, single pulse measuring angle pure delay, wave control pure time delay, probe installation zero and angular velocity zero error on the disturbance rejection rate and the guidance loop are analyzed. On the condition of a same error source, the difference on extracting the angular velocity of the line of sight and the influence on guidance performance are compared among the whole strapdown phased array radar seeker, the platform parabolic radar seeker and the platform-based phased array radar seeker. Results show that the beam calibration error and radome error are the main reason impact disturbance rejection rate positive feedback, and platform-based phased array radar seeker can significantly reduce the influence of beam calibration error.To explain better the risk of the whole strapdown phased array radar seeker positive feedback instability, and aiming at the limitations of calculation method for isolation, a seeker isolation index calculation method which introduced guidance loop and the mapping of disturbance rejection rate and miss distance is proposed. A typical radar seeker error source of to-air combat is established to analyze its impact on miss distance with different disturbance rejection rates. On the consideration that disturbance rejection rate amplitude fluctuations may occur in practical engineering situation, isolation amplitude index is judged synthetically in four aspects, including miss time, miss distance divergence speed values, disturbance rejection rate amplitude margin and dimensional miss distance threshold. Based on the index calculation, the segregation index and the corresponding error precision are distributed between the whole strapdown phased array radar seeker and platform-based phased array radar seeker. Results show that the index of disturbance rejection rate positive feedback on the typical surface-to-air condition is strict, and platform-based phased array radar seeker can eliminate the influence of beam control error compared with the whole strapdown phased array radar seeker.Under the condition that the level of seeker isolation is determined, Seekers with different nature on disturbance rejection rate and amplitude have different effects on the guidance control circuit. The disturbance rejection rate formation mechanism is analyzed for this. Based on the guidance control circuit, an analysis method in the frequency domain with more intuition is introduced. Main reasons causing the seeker isolation involve platform isolation performance, radome slope error, probe scale, dynamic inconsistency, signal delay inconsistent and so on. Considering influence of the disturbance rejection rate positive feedback, proportional navigation coefficient, simulation order number, angle of attack time constant and terminal guidance time constant design all have effect on the disturbance rejection rate. Finally, the parasitic loop is introduced to analyze frequency domain of guidance commanding to overload response for the seekers with different structures. Analysis results are shown as follows: Only the platform-based seeker isolation property is the negative feedback; The influence of other factors will greatly increase the probability of positive feedback; Navigation ratio coefficient should be designed to be small and angle of attack time constant should be designed as small as possible; The terminal guidance time constant need to be designed properly; The effect of positive feedback mainly concentrates in low frequency band; The influence of negative feedback mainly concentrates in high frequency band.