THE LOGARITHMICALLY PERIODIC RHOMBIC ANTENNA.
STANFORD RESEARCH INST MENLO PARK CALIF
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The possibility of using a logarithmically periodic, concentric, rhombic antenna array for ionospheric sounding in the HF region is considered, both theoretically and experimentally. In particular, the feasibility of simultaneous excitation of n elements within a larger, m-element array is examined in detail. For a logarithmically periodic array, the group of any n neighboring elements forms a module whose properties are identical with those of any other similar module, except for a scale factor in frequency. A mathematical representation is developed which describes the behavior of such an n-element module independently of rhombic angle and height-to-leg length ratio. The important parameters of the calculation are the number and relative sizes of the elements within the module. It is shown, on the basis of the theory, that a module of three elements having a size ratio of 1.5 to 1 between successive elements should give a considerably lower side -lobe level over a larger frequency range than is typical of the single-element rhombic antenna. A design procedure is described for arrays intended for operation over large frequency ranges. This procedure is applied to a specific case, leading to a five-element, three-module array for operation over the range 4-36 Mc. The results of radiation pattern measurements on two different antenna models are presented. Author
- Atmospheric Physics
- Electrical and Electronic Equipment
- Test Facilities, Equipment and Methods