Fast tunable active receiving antennas

Authors

  • J. F. Hopf,

  • H. K. Lindenmeier


Abstract

With mobile RF communication systems, sensitivity and linearity characterized by the dynamic are the main important qualities of the system on the receiving side. Up to now, especially in the low frequency and the short wave frequency range this problem has not been solved satisfactorily with professional passive antenna systems even though heavy filters are used. Considering nonlinear effects and taking the electromagnetic pulse problem (emp) into account, the short selective active receiving antenna is the optimum solution to this problem. A formula is derived for the field strength sensitivity of the selective active rod antenna. Taking the external noise into account, the minimum height of the antenna is evaluated with respect to optimum sensitivity as well as with respect to minimum nonlinear distortion of the amplifier, which means optimum dynamic range. Antenna heights and dynamic range of the selective active antenna are compared to different systems such as active broadband antennas and standard receiving systems with passtive antennas. For sensitivity reasons, capacitive antenna elements must be tuned by inductive means. In combination with a special switching strategy, premagnetized ferrite inductances are appropriate tuning elements. Nonlinear effects in the ferrites, however, are one of the main problems with electrically tuned antennas, which therefore are taken into account as well.

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