The multi-band, multi-pitch antenna

A new design of multi-band, broadband multiple pitch helical antenna is presented. The proposed antenna is applicable for the use of portable transceivers to cover two bands of operating frequencies. The first band covers 150 MHz to 174 MHz. The second band covers 764 to 870 MHz. Dividing the helix into multiple segments with different pitches and number of turns to create multiple, overlapping resonances, a VSWR of better than 2:1 is achieved from 764 to 870 MHz. Also, by using a simple, two-element high-pass matching circuit, the antenna is matched to 50 ohms from 150 to 174 MHz without affecting the response in the second band. The radiation patterns of the antenna mounted on a portable radio chassis exhibit the characteristics of a dipole in both bands. The helical antenna remains as a single feeding, single element antenna.