Research On SLF H-Field Towed Antenna Techniques

By means of attaching a H-field loop antenna to the cable of electrode-pair antenna, we can achieve omni-directional reception in the SLF communication to the submarine. The noise of loop antenna is higher in voltage level and more complex than that of electrode-pair antenna. This dissertation studies theoretically various noise sources in the H-field antenna, finds the expressions of thermal noise, motion-induced noise, magnetostrictive noise and barkhausen noise ENF, analyzes the contributing of key factors as cable vibration, cable electricity characteristic, cable mechanical characteristic and geomagnetic field, provides the way to reduce these noises. To reduce the thermal noise ENF, high reversible permeability core material should be used; To minimize the motion–induced noise, the antenna sensitivity profile should take parabola type. To reduce magnetostrictive noise, sensitivity profile should be more smooth, core should take"zero-strain"structure. To reduce barkhausen noise, SLF receiver should include degaussing control circuit. There is conflict between these requirements and we should provide a total optimize configuration. Antenna winding should be dense winded in single tier with aluminium material, use pre-programmed winding machine to achieve a parabola turn density, the core should form"zero-strain"structure with 4-79 permalloy tape. The best winding/core radius ratio can obtained from the known electrode pair antenna parameters and buoyant condition, while the core reversible permeability and relative density are realizable, antenna resistance, inductance and effective length are in a suitable range, thus the design to reduce thermal noise and motion-induced noise is feasible,besides, the noise figure satisfies the design requirement. The degaussing circuit can keep zero level axis direction flux to decrease magnetostrictive noise and barkhausen noise, the dissertation discusses the principle and scheme of degaussing control circuit.