MINISTRY OF EDUCATION AND TRAINING MINISTRY OF NATIONAL DEFENSE ACADEMY OF MILITARY SCIENCE AND TECHNOLOGY LE VAN SAM DEVELOPMENT A METHOD OF IMPROVING THE INFORMATION QUALITY OF MEASURING AND TRACKING THE TARGET IN A MODERN MISSILE GUIDANCE STATION Major: Control Engineering and Automation Code: 52 02 16 SUMMARY OF PhD THESIS IN ENGINEERING HA NOI – 2019 The thesis was completed at ACADEMY OF MILITARY SCIENCE AND TECHNOLOGY Scientific Supervisors: Assoc Prof Dr Vu Hoa Tien Dr Tran Ngoc Quy Review 1: Assoc Prof Dr Pham Trung Dung Military Technical Academy Review 2: Assoc Prof Dr Tran Duc Thuan Academy of Military Science and Technology Review 3: Dr Tong Xuan Dai Air force – Air defence Technical Institute The thesis was defended in front of the Doctoral Evaluating Committee at Academy level held at Academy of Military Science and Technology at ………/………, 2019 The thesis can be found at: - The Library of Academy of Military Science and Technology - Vietnam National Library THE SCIENTIFIC PUBLICATIONS Vu Hoa Tien, Tran Ngoc Quy, Le Van Sam, 2016, “Study the ability of automatically stabilize the receiver dynamic range of the new-generation fire-control radar systems”, JMST, Academy of Military Science and Technology (Special issue9/2016), Pp 57-66 Vu Hoa Tien, Tran Ngoc Quy, Le Van Sam, 2017, “Studying and proposing solutions to automatically control the receiver’s input dynamic range of the new-generation fire-control radar system”, JMST, Academy of Military Science and Technology (49, 6-2017), Pp 09-17 Vu Hoa Tien, Le Van Sam, Tran Ngoc Quy, 2017, “Development of the software algorithm for automatic detection nonlinear distortions of a useful signal in the receiving path in the fire control radar with a large dynamic range”, “Natural and Engineering Sciences Journal” (ВАКRussian) №10 (112) , 2017, Pp 91-96 Le Van Sam, Vu Hoa Tien, Tran Ngoc Quy, 2018, “Synthesizing the automatic overload prevention transmit receive system in fire-control radar” JMST, Academy of Military Science and Technology (55, 6-2018), Pp 03-15 INTRODUCTION Urgency of the thesis In missile guidance stations, accuracy of measuring coordinates of target and missile is particularly important, which is one of the decisive factors to destroy a target of a missile Input signals of the target and missile tracking systems obtained from the corresponding receivers are video or digital signals If the input signals are distorted or unstable, the performance of the tracking systems will be reduced Studying the ability of automated receiving and processing target signals in front of the coordinates target tracking system based on synthesizing the closed receive-transmit control system is the urgency mater Research results not only improve the input signals quality for target tracking systems, but also upgrade the level of automation for the fire control radar systems, which are particularly important in the modern warfare Purpose of research Research on the ability of enclosing the receive-transmit system of fire - control radar to become the closed-loop control system which automatically eliminating receiver overload problems based on synthesizing the new overload discriminator and transmitter controller Object and scope of research The general object are air defence fire control radar systems and the specific object is the receive-transmit target tracking systems of air defence missile guidance stations The result scope is synthesizing the closed loop receive-transmit control system to automatically eliminating overload receiver problem in the receive-transmit target tracking system of air defence missile guidance stations Method of Research - Theoretical methods: automatic control; modeling system; modern signal processing… - Method of calculating and synthesizing models on digital computers - Verification method; empirical statistics; simulating processes on digital computers; comparative control Practical and scientific significance - The thesis has contributed the results of theoretical research to synthesis the closed loop receive-transmit control system automatically eliminating overload receiver problem for radar systems in general and for the target tracking system of air defence missile guidance stations in particular Structure of thesis The entire of thesis consists of 131 pages, chapters, 55 figures, 11 tables and 11Pps appendice Chapter OVERVIEW OF FACTORS AFFECTING ON THE PERFORMANCE OF TARGET COORDINATE MEASURING TRACKING SYSTEMS IN THE FIRE CONTROL RADAR 1.1 Overview of the air defence missile guidance stations, the role of the tracking channel and the need to maintain the performance of the target coordinates measuring-tracking systems 1.1.1 General overview of air defence missile guidance stations The basic components of general missile control system are shown in the Fig.1.1 Transmitter system Target Receiver for target tracking Missile Receiver for missile tracking Synchronous system (εmt,βmt,rmt) Control command block (εtl,βtl,rtl) Transmit control command (λε,λβ,K3) Radio-frequency transmission line Fig 1.1 The basic components of general missile guidance station In that system, the functions of coordinate-tracking systems are measuring angular, distance coordinates of both objects (targets, missiles) 1.1.2 The role of target tracking chanel in missile guidance stations The target tracking system is one of the main compornents of the missile control system Improving performance of processing the target signal is directly related to improving the input signal of coordinate tracking systems and the quality of control information in the missile control system 1.1.3 Influence of input signal quality to the precision of determining the target coordinates of the tracking systems in a missile guidance stations Distortion and instability of input signals will directly decrease the performance of the target tracking system 1.1.3.1 Effect of unstable amplitude and distortion of input signal to the performance of the range and speed target tracking system in missile guidance stations Acccuracy of tracking a target is mainly dependent on perfomrmance of range and speed discriminators From analyzing the effects of amplitude instability and distortion of the input signal on accuracy of tracking target can draw the following comments: - Comment 1.1: If the amplitude of the Uv signal changes, it will lead to a change of transmission coefficient (K ± ΔK) in discriminator If the signal is distorted, its center of energy is shifted (∆’τ) and delay error is: ∆τ=∆τ0±∆’τ In order to measure the Doppler frequency, a two-channel frequency-difference discriminator (BPB-Vmt) is used Comment 1.2: Distortion and amplitude instability of input signal can lead to distort the frequency characteristic of speed discriminator The distortion of discriminator characteristic depends on the distortion of input signals 1.1.3.2 Effect of unstable amplitude and distortion of input signal to the performance of angle target tracking system From the expressions of measuring angle errors, can draw the comment: the distortion and unstable amplitude of input signal will reduces the quality of the angle-tracking system 1.2 Overview of the methods to stabilize amplitude and shape of input signal of the target measuring – tracking system in the fire control radar systems 1.2.1 Factors affecting on the instability and distortion of input signal of the target coordinate tracking system in the fire control radar Two main factors are concerned: - Amplitude of input signal is too large - Distortion of the output signal induced by receiver overload problem To visually display the signal distortion caused by overloading the receiver, we consider the amplifier’characteristics of the receiver (Fig 1.10) Nonlinear Uout amplitude Uout Uin Uout t Nonlinear distort signal Linear amplitude range t Fig 1.10 Amplifier’ characteristics of the receiver over signal distortion phenomenon 1.2.2 Overview of the methods to improve stability and decrease distortion of input signals of the target coordinates measuringtracking system 1.2.2.1 Overview of methods to stabilize the amplitude, decrease distortion of the input signal of the target coordinates measuringtracking system The Receive-transmit system in target tracking chanel of fire control radar is usually not a closed loop control system (Fig 1.11) To adjust K, use a combination of methods [25], [47] including: Decrease the input signal (attenuator); automatic gain adjustment (AGC); manual amplitude adjustment; switching power transmission AT RF transmitter Impulse modulator Synchrounous IF receiver Video processing MT RF receiver AT Target tracking systems Fig 1.11 The transmit/receive system as a opened loop control system 1.2.2.2 Some comments on methods of stabilizing the output amplitude and eliminating overload receiver problem - Use of both manual and automatic methods: AGC; MGC; ATT; change the transmit power to stabilize and prevent signal distortion - The timing and magnitude of manual adjustments are subjective, which causes an undesirable delay and signal distortion Those directly reduce the signal quality of input signal of the target coordinate measuring- tracking system 1.3 Determining the research problems of the thesis Synthesizing algorithms and structure of the closed-loop transmit/receive control system automatically eliminating overload receiver problem in fire control radar system Four problems have been identified: Surveying and building the power characteristic and amplitude characteristic of reflected signal at the input of receiver over distance and radar cross section (RCS) of the target Building the amplitude characteristic of receiver in terms of target’distance and RCS changing in all its range Synthesizing the detection algorithm, control algorithm and suitable structure for closed loop transmit/receive control system Simulating, surveying, evaluating the effectiveness of the system Antenna Target Antenna RF transmitter RF receiver Impulse modulator Controller Receiver Overload discriminator Tracking systems Fig 1.16 The structure of a transmit/receive automatically eliminating the overload receiver problem 1.4 Conclusion of chapter Stabilizing the input information of the tracking systems is directly improving perfomance of the tracking systems The automatically preventing distortion and stabilizing amplitude of input signal based on synthesizing the closed loop transmit/receive control system is the effective method to improve the quality of input signal of the target tracking system in the fire control radar system Chapter PROPOSING A METHOD OF PREVENTING THE RECEIVER OVERLOAD PROBLEM BASED ON ANALYSING SIGNAL CHARACTERISTICS 2.1 Choosing the object and model to survey 2.1.1 The object for surveying, analysing The object studied in this chapter is an transmit/receive system of the fire control radar Serveying is done with a tracking target chanel 10 Fig 2.8 The changing range of the receiver's input signal amplitude according to the target’s distance and target’s RCS 2.3.2 Surveying the changing of amplitude characteristic of input receiver signal over adjusting the transmitter power and attenuator parameters 2.3.2.1 Adjusting the transmit power Following the real parameters of the fire control radar [11], highfrequency generator can work in the following power modes: maximum P0 = 75kW; average P01 = 7.5kW; Low P02 = 750W Thus, the transmitter power can be adjust twice: P0P01 and P01P02 a) First adjusting transmitter power survey: Reduce P0P01 when the receiver overloads, the amplitude of receiver input signal was reduced, as shown in Figure 2.10 b) Second adjusting transmitter power survey: (P01P02) : The results are shown in Fig 2.11) Fig 2.10 The changing of receiver signal amplitude at the first adjusting P ph Fig 2.11 The changing of receiver signal amplitude at the second adjusting Pph 11 2.3.2.2 Using the receiver input attenuator (ATT) The ATT used for the survey has attenuation levels: 8dB; 18dB; 26dB The simulating attenuation levels including: a) 1st level (SG1- point fig 2.12) b) 2nd level (SG2- point fig 2.13) c) 3rd level (SG3 - point fig 2.14) Fig 2.12 The changing of the signal amplitude with SG8dB attenuated Hình 2.14 The changing of the signal amplitude with SG26dB attenuated Fig 2.13 The changing of signal amplitude with SG18dB attenuated Comment 2.6: After times controlling receiver signal amplitude (2 times of reducing the transmitter power, times of increasing the attenuation levels, the receiver can be maintained not overloading, in term of the target’s RCS is 100m2 and target’s range is 300km (Figure 2.14) 2.4 Synthesizing the algorithm to prevent overloading of receiver 2.4.1 Synthesizing the control algorithm (fig 2.15) 2.4.2 Control characteristic to prevent overloading of receiver With schematic diagram 2.15; MATLAB-SIMULINK software; real parameter of fire control system [9], [11] and the target as described in Section 2.3 2.1, the simulating of synthesized control algorithm (Section 2.4.1) was performed The results show that the signal amplitude of receiver input can be automatically controlled into the receiver dynamic 12 Fig 2.15 Flowchart of algorithms to control transmitter power and attenuator Fig 2.16 Characteristic of the signal amplitude applying the control algorithm range, and overloading receiver problem is automatically eliminated (Figure 2.16) This algorithm only applies to a specific target, as shown in the example 2.5 Conclusion of chapter In Chapter 2, essential characteristics were investigated, which are necessary for synthesizing the proposed detectors and controllers However, the synthesized algorithm can only applied to a specific target The algorithm applied to any arbitrary target was synthesized in Chapter Chapter SYNTHESIZING ALGORITHM AND STRUCTURE FOR THE OVERLOAD DISCRIMINATOR AND CONTROLLER OF AUTOMATICALLY PREVENTING RECEIVER OVERLOAD 3.1 Synthesizing algorithm and structure for the receiver overload discriminator 13 3.1.1 Basis for Synthesizing the algorithm for the receiver overload discriminator 3.1.1.1 The nonlinear distortion of signal causes its spectral distortion a) Nonlinear distortion of the signal due to overloading of the receiver If receiver is overloaded, its output signal will be nonlinear distortion [13],[42] (fig 3.1) Fig 3.1 Explain the nonlinear distortion of the signal in a receiver b) Portrait pectrum of a signal before and after nonlinear distorted 3.1.1.2 Surveying spectrum characteristic of receiver output signal Results of survey: Characteristic of the signal spectrum before the overloaded receiver (fig 3.3) Characteristic of the signal spectrum after the overloaded receiver (fig 3.4) Fig 3.3 Spectrum of the receiver output signal when not overloaded Fig 3.4 Spectrum of the receiver output signal when overloaded 3.1.1.3 The evaluating of survey results and comments Evaluate: When the receiver is not overloaded, the amplitude of the spectrum lines far from the center frequency is very low and stable The amplitude of the side lobes will increase corresponding to the level of overload 14 Comment: It is possible to use the feature of changing the amplitude of high frequency spectra lines for detecting the timing when the receiver is overloaded That based on constructing the relationship between the amplitude of the "mth" line and power (Ppx) of the receiver input signal, ie: (3.16) Smt (mf)=G[10log(p px )] 3.1.2 The reliability of the receiver overload detection method based on monitoring the amplitude of a defined spectral line This was evaluated based on the factors influencing the signal spectrum (in the thesis) 3.1.3 Synthesizing the algorithm detecting receiver overload: Including the function of preventing receiver overload and rejecting function * Condition for overload signal "j=1": - The amplitude of "mth" spectrum line is bigger than the threshold level (NG) - Receiver output voltage: Ura>Ungương_max=Ura_0 * Condition for “Q”(Rejecting one level of preventing receiver overload methods which was using): - The AGC voltage decreases down to: UAPY