Design and swept-frequency measurement of printed circuit board log-periodic dipole arrays

This paper describes the design and measured performance of printed circuit board (PCB) log-periodic dipole arrays (LPDA's) etched on dielectric substrates. The design method is described in terms of a simplified flow chart for an interactive computer program. Design techniques for conventional LPDA's are modified to take into account the presence of the dielectric layer between the dipole elements by using an effective relative permittivity. The output from the PCB LPDA computer program is used to generate a computer tape to drive an auto-coradograph which scribes a scaled up version of the required artwork onto rubilith. The computer program plus tape relieves the antenna designer from the chore of manual computations and artwork layout. Swept-frequency measurement techniques are used to examine the performance of two PCB LPDA's.