Optimal Bandwidth Positions for a Terminal Embedded Antenna: Physical Bounds and Antenna Design

This article considers a small embedded planar antenna in a square-shaped terminal of 25 cm
²
at a frequency band near 900 MHz, intended for long-range communication. This article aims to shows how the Q-factor bounds can be used to predict the performance of such an antenna. Both to determine the optimal bandwidth and the variations in the total efficiency but also to help to inspire the antenna design shape. The choice of shape and position impacts both bandwidth and efficiency. The latter is illustrated by a center-edge positioned folded inverted F-antenna with higher efficiency, as compared to, a more bandwidth optimal meander antenna at the corner. Fabrication and measurements show that the corner positioned antenna is close to bandwidth optimal, and also that it and the associated optimal current have a similar radiation pattern.