ANTENNA DESIGN ONERS SMALL-SIZE WITH WIDE BANDWIDTH

PATCH antennas formed with high-dielectric-constant (epsilon) thick su bstrates are being used to satisfy the size requirements of portable s ystems such as radio pagers and cellular handsets. The use of a thick substrate reduces the patch dimensions by increasing the effective wid th. However, high-E material also reduces the operating bandwidth whil e the use of thick substrates increases surface-wave effects, which de grades performance. An alternative is to employ a patch antenna that i s short-circuited at one end. This approach results in a patch size th at is half that of an open-ended antenna at the same resonant frequenc y. A simple closed-form equation can be used to calculate the input im pedance of these compact antennas.