Practical considerations in the design of pager loop antennas

Frequently, a loop antenna is mounted on a printed circuit board, which functions as a small ground plane, and placed in proximity to electronic devices (receiver, transmitter, amplifier, etc.), batteries and possibly other components such as a vibrator. Consequently, it is important to know how the packaging environment influences antenna performance. This paper presents moment method calculations for a model of a typical pager unit. The wire-and-surface computer model used for the calculations is illustrated. Results are presented which show the effect the ground plane and components have on the antenna performance characteristics such as gain, input impedance, polarization and pattern coverage. In addition, we discuss various loop design alternatives, including bent loops, "half loops" which are terminated on the ground plane, and multi-turn loops.