MATHEMATICAL MIXER MODEL WITH FORMATION OF HETERODYNE ANTIPHASE SIGNAL

Objectives To carry out calculations involved in the design of a microwave mixer with a diplexer with the formation of the antiphase heterodyne signal using a slot resonator.Method In order to calculate and optimise the characteristics, design and topological parameters of microwave mixers, the results of the design bandpass filter  PF and low-pass filter (LPF) mixers of through-feed type were used. The characteristics of mixers and their structural elements were calculated using the Serenade software package intended for the automated calculation of microwave devices. A distinct feature of designing mixers (with a diplexer) involves the need to optimise the topology of the diplexer before optimising the mixer characteristics.Results The characteristics of nonlinear distortions show that the maximum power level at the mixer inlet should not exceed -15 – -20 dBm. In order to attenuate the intermodulation distortions of the 3rd order, this level should be higher that 50 dBs. The relatively low level of compression and suppression of harmonic and intermodulation distortions associated with the minimisation of the heterodyne power level at the calculation of characteristics of mixers of the required heterodyne power level (Rh ~ 5-7 dBm) is due to the minimum expenses at the realisation of sources of heterodyne signals. A noticeable improvement in the characteristics of mixers by nonlinear distortions can be achieved by shifting the operating point at the points on the current-voltage characteristic (VAC) diodes by an external voltage source with a simultaneous increase in Ph by several dB (up to Ph = 10 dBm).Conclusion A mode of increased nonlinear distortion suppression can be practically realised by switching on diodes through resistive-capacitive circuits (auto-shift) or using diodes with an increased potential barrier. The calculation shows that it is possible to realise sufficiently small conversion losses of 6.6-8.0 dB at low levels of Rh ~ 5-7 dBm

IDENTIFICATION OF AIR RADAR TARGETS USING THE DOPPLER EFFECT FROM A HEATED JET ENGINE

Objectives The aim of the study is to develop a methodology for identifyingaircraft by the deflections of an electromagnetic radar beam by a heated jet engine. Methods Atoms of the crystal lattice of the metallic parts of the operating jet engine will be in a state of chaotic Brownian motion due to heating. The electromagnetic beam, falling on these atoms, will change its frequency in accordance with the Doppler effect, by means of which the spectral electromagnetic radiation component will expand in direct proportion to the magnitude of the engine temperature. When determining the width of the spectral line of the direction-finding radio emission, it is possible to accurately identify the temperature of the aircraft in order to avoid false targets.Results When locating aircraft having a working jet engine, it is possible not only to determine the coordinates of the target, but also to identify the heated engine. Due to the use of high-precision methods for identifying heated sections, the direction-finding targets may be classified, the spatial orientation of both the aircraft itself and its control planes to be determinedand the direction of the thrust vector control of the jet engine calculated.Conclusion The application of an innovative technique for direction-finding air targets will allow the radar targets to be identified with high accuracy against the background of active and passive interferences. In addition, when analysing the information on the magnitude and direction of the jet engine thrust and the position of the aircraft controls, it is possible to determine not only the coordinates of the direction-finding object, but also to proactively identify the manoeuvres to be performed