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The fundamental problem of the transmitters protection against microwave energy reflections from aircraft antenna is discussed. The paper presents some applications of active and passive isolators and circulators as a tool for reflections protection. It has been stated that electrical properties of ferrite isolators and circulators grow worse at lower operational frequencies (below 50 MHz) and temperatures (cryogenic). Semiconductor magnetoplasma exhibits gyrotropic effects similar to those of magnetized ferrites and can solve the problem non-reciprocity in the HF range from 3 to 30 MHz, which is important for HF communication. The semiconductor device realization, optimal parameters, and operational temperature range, based on minimum forward loss α and maximum reverse attenuation β, were chosen. Major electromagnetic parameters of semiconductor isolators were determined. Ferrite circulators and isolators are the key elements in modern microwave engineering. Their fundamental property of non-reciprocity is capable of simplifying the construction and improving the stability, efficiency and accuracy of radar, communication and testing systems. The devices contain a core of ferrite biased by a static magnetic field. This field orients the electron spins within the ferrite to produce a gyromagnetic effect. The non-reciprocity occurs when radio frequency (RF) signal interacts with the precessing electrons to set up a standing-wave pattern within the core.

Protection of HF Transmitters from Reflection Failure by Help of Semiconductor Isolators