Log periodic dipole arrays

A new class of coplanar dipole arrays is introduced. The antennas described provide unidirectional radiation patterns of constant beamwidth and nearly constant input impedances over any desired bandwidth. The broad-band properties are achieved by making use of the principles of log periodic antenna design. Models are discussed which are capable of providing 8- to 9-db directive gain with an associated input standing wave ratio of 1:2:1 on a 75-ohm feeder, and this performance is independent of frequency. The free-space properties of several of these arrays have been measured and the results are presented. The antenna configuration is simple, permitting practical methods of fabrication, and the design should prove useful in many applications. It makes possible, for example, the construction of "all-wave" rotatable beams of very low cross section for use in the hf to uhf spectrum.