Research On Explosive Magnetic Generators Of Frequency And Its Measurement Method Of Radiation Characteristic

With rapid development of electromagnetic pulse (EMP) technology in field ofscience research and military affairs, the EMP generation technology by nonnuclearmeans becomes one of the hot domains home and abroad. Helical ExplosiveMagnetic Generators of Frequency (EMGF) is miniaturization equipment whichgenerates and radiates EMP using magnetic flux compression theory. Based onequivalent circuit, EMGF is designed and optimized through method of theoreticalresearch, simulation calculation and experimental measurement, and a novelmulti-pulse generator is proposed. EMP radiation field measurement method whichis fit for output characteristic of EMGF is researched, and especially each frequencyband of the receiving antenna is optimizational designed. This work will explodenew thinking and method in the field of EMP generation and its radiation filedmeasurement.EMGF researched in this thesis develops from Magnetic Flux CompressionGenerator (MFCG). Based on magnetic flux compression theory, the basic theoryand classification of MFCG are introduced. According to structure characteristic ofEMGF, theoretical calculation method of circuit resistance is analyzed consideringthe ohm loss in almost ideal status. The calculation model of coil inductance whichconsidering the effect of armature shield on stator coil is proposed which make thefoundation of equivalent circuit calculation. The EMGF equivalent circuit is a RLCseries circuit. The effect of each parameter in the circuit on operation current isanalyzed by numerical method. It contains influence of parameters of changing rateof inductance, inductance initial value and exploded time on generator current, andit is proposed that when the coil inductance decreases by the rate of fast followed byslow, the load current is fit for electromagnetic radiation; to connect with highresistance load, the model connected load with transformer is proposed, and theinfluence of transformer parameter on output energy and current is analyzed toimprove transform efficiency; the influence of situation, manner and value ofcapacitor connected to circuit on output current is analyzed, and connecting way ofcapacitor in the circuit to get magnified current or energy is proposed. Thesemethods and models are the consultation for EMGF design.To generate multi-pulse with same frequency and broaden the EMP workingfrequency band, a novel switch-type multi-pulse generator model is proposed basedon helical EMGF model. This generator consists of armature, pin switch, storagecapacitor and load resistance. Some pins are located in the direction of armature axis.The pulse wide and distance between pulses are controlled by the parameters of explosion velocity and pins distance. The multi-current pulses are generated by thestorage capacitor discharging in the circuit. The current output characteristic in theload is controlled by structure parameter of the generator. This designed model doesnot have the function of energy amplification, but can produce high power pulse andhave the merit of simple structure and miniaturization.EMP measurement method is designed for accurately measuring radiationcharacteristic of EMGF, including output current and EMP radiation field. Currentin load is measured by Rogowski coil and a self-integral Rogowski coil is developed.For the EMP radiation field measurement, as the generator covers1MHz to tens ofGHz frequency band, segment measurement scheme according to differentfrequency band is proposed, and the receiving measurement antennas are simulatedand optimized. For the radiation field measurement in1MHz~50MHz frequencyband, an experiment method is designed which includes using small loop antenna tocouple magnetic field in space, and deducing radiation power of generator in eachfrequency. For the antenna operated in50MHz~2GHz frequency band, to realizedminiaturization design, metal ridge loaded and lossy medium distributing loadedTEM horn antenna model is proposed, and its impedance and radiating character aresimulated and experiment validated. For the antenna operated in2GHz~25GHzfrequency band, to realized high gain character, dielectric lens loaded TEM hornantenna model is proposed, and its impedance and radiation character are simulatedand optimized; otherwise, small angle TEM horn antenna which increases utilizationcoefficient of aperture is proposed, and its impedance and radiation character aresimulated. The results show that the two improvement methods both can realize highgain design.Operation characteristic and radiation characteristic measurement method ofhelical EMGF are researched in detail. The effect rules of inductance and capacitorin equivalent circuit and resistance parameter of load on improving outputcharacteristic of system are proposed, which provides theoretical consultation forgenerator design. A novel switch-type multi-pulse generator is proposed which canproduce multi-pulse in the same frequency. A frequency division radiation fieldmeasurement method for output characteristic is proposed, which is the consultationfor radiation characteristic measurement of EMP generator.