Realistic Performance of Tightly-Integrated 2.4 GHz Antennas for Minimum-size PCB-based Wireless Sensor Systems

This paper presents simulation and measurement results from a variety of compact PCBbased antenna designs suitable for wireless systems operating at 2.4 GHz using realistic implementation conditions in contrast to idealized, best-case, configurations. In particular, the input impedance, radiation pattern, and radiation efficiency were measured using a variety of simulated and physically constructed prototypes and test fixtures. The results were compared with published application notes and manufacturer specifications to obtain better estimates of antenna performance in implementations, such as centimeterscale wireless sensor nodes with size and/or weight constraints. Notable deviations from published expectations of performance were exhibited in both simulation and measurement, including absolute gain, input impedance, and radiation pattern. Reasonably high radiation efficiency was also demonstrated. Significant deviations from both simulation and manufacturer-published results were observed in all investigated parameters. Differences from datasheet values of as much as 11 dB in antenna match and 12 dBi in maximum gain are reported. These results indicate a number of important considerations for a wireless sensor system designer, including that chip antennas are highly preferable to PCB trace antennas if cost is not a concern, implementations of designs tend to decrease directivity, and as much as half the efficiency expected from simulation is seen in realistic implementation.