Diversity antenna design for use in UMTS/high-speed packet access-based data cards

This study theoretically analyses the envelope correlation coefficient of diversity antennae by adopting field analysis of two infinitesimal dipoles. To validate the proposed model, the theoretical results for the simulated correlation coefficient of two antennae with the same orientation are then plotted for comparison with those obtained using Clark´s approach and those computed using measured far-field patterns of two identical meander-line folded monopole antennae, showing well agreement. Thereby, by employing the proposed approach, the assessment of the envelope correlation coefficient can be done quickly to determine diversity antenna´s configuration when designing an embedded diversity antenna on a compact flash data card. Two antenna configurations (type-l and -II) are proposed for experimental study. Measurement results of the experimental study indicate that the envelope correlation coefficient is less than 0.1, the isolation is below -17 dB, and the average gain in the primary/auxiliary antennae exceed -3.5/-8.4 dBi, respectively. Antenna performance is acceptable, validating this design approach with a highly compact size (primary antenna, 5 × 34 × 5 mm³; auxiliary antenna, 9×4×1 mm³ for type-ll configuration) experimentally.