The megawatt pulsed power magnetron operating in the L-band was designed based on magnetrons produced in the past at Kubara Lamina. Unlike its predecessors, it is characterized by much higher operating parameters: supply voltage and anode current, which translates into an increase in the obtained output power. The magnetron was designed using software for numerical simulations of the interaction of an electric charge with an alternating electromagnetic field (Particle in Cell - PiC). Aspects such as microwave matching of individual components of the device and thermal resistance of the entire system, including the appropriate type of cooling, have also been subjected to numerical analysis. In order to obtain the proper parameters of power supply of the tube, a dedicated impulse modulator powered by supercapacitors was build. The modifications allowed to obtain a power signal with a sharp and stable edge and a pulse length of the length of single microseconds. Obtaining the optimal power source had a key impact on the tube’s operation. The measurements of tube output power in the waveguide system with dummy load were carried out, during which the output power of the megawatts range was obtained. This magnetron is a tube with the highest output power among the microwave tubes ever designed in the Kubara Lamina Company and probably throughout Poland.
Kubara Lamina is working on the development of a new type of pulsed-power magnetron with megawatts output power operating in the L-band. An important part of the design work are computer simulations of electromagnetic interactions with an electric charge. In order to get the most reliable results, the task was carried out with the help of specialized calculation software from two independent producers - CST Studio Suite and MAGIC Tool Suite. The results obtained with the help of both programs were similar, but there were differences between them resulting from the specific features of the software. The differences concerned the time needed to create an electron spokes in the interaction area between the cathode and anode of the tube as well as the threshold voltage at which the generation of high frequency oscillation began. On the basis of numerical simulations, the optimal geometrical dimensions of individual details were obtained and the magnetron prototype was created. The tube was subjected to laboratory tests under dynamic conditions. To ensure proper input power parameters, a dedicated impulse modulator powered from supercapacitors batteries was constructed. The energy of the electromagnetic wave generated during the dynamic operation of the device was absorbed in the waveguide ended with high power load. The test results obtained under the experimental conditions allowed to verify the structure of the model designed using simulation software. Tests in the available power range of the power supply confirmed very good compatibility of the tube parameters with the results of electromagnetic simulations. An additional advantage of carrying out the simulation was the shortening of the design process, because the first model of the device already worked in accordance with the technical assumptions.
A magnetron as a generation lamp is a groundbreaking invention. Magnetrons can achieve high power in both continuous and impulse mode. In addition, their characteristic feature and at the same time a great advantage is the high efficiency in the decimeter frequency range. Moreover, they have a very good ratio of power generated to mass compared to semiconductor solutions. The purpose of this study was to investigate the stability of the oven magnetron in terms of emission of undesirable signals. The aim of magnetrons of this type is to produce a continuous electromagnetic wave with stable oscillations of 2.45 GHz. During experimental research, additional spurious frequency of 4.3 GHz was observed in some cycles. Such spuria adversely affect the stability of the generated signal and disturb the surroundings. To find out why the signal is generated, the oven magnetron is examined. After that the numerical analysis was performed on this basis. The analysis shows that the magnetron operates in a different mode than the basic mode π. Numerical studies in the form of computer simulations were carried out in the CST program. To do this magnetron geometry was implemented in to the program. For experimental measurements, a commercially available oven magnetron was used. During the tests, the operation of a continuous wave generator with a frequency of 2.45 GHz and operating in the power range of 200-800W.
One of the most important parameters that characterize microwave tubes with crossed fields, both amplifiers (CFA), and generating tubes like magnetrons is the noise level. This type of tubes are characterized by relatively high noise levels, which is the main factor limiting their current use in radar transmitters. The main source of noise in microwave tubes of this type is the dispersion of the energy of electrons that are in phase with the spatial wave of the electromagnetic field propagating in the delay line (in case of an amplitron) or in the resonant structure (in case of a magnetron).The results of the research presented in the article concern the technique of determination of Signal to Noise Ratio (SNR) based on the analysis of results obtained during the numerical simulations of the effect of electric charge on a high frequency electromagnetic field. Signal to noise ratio was determined by analysing in-phase and quadrature data recorded in the high frequency simulation. In order to assess the accuracy of the method under investigation, the results from the noise analysis obtained from numerical calculations were compared with the results obtained from real tube measurements performed by a spectrum analyser. On the basis of the research, it appears that performing analysis of noise generated in the interaction area may be useful for preliminary evaluation of the tube at the design stage.