A slot-fed U-slotted patch antenna is developed as an aperture-coupling structure, and is compared to the existing feed types. Its wideband mechanism is explained, and its samples for Ku- and S-bands are designed, simulated, and tested. A bandwidth of about 42% for VSWR less than 2:1; and 30.1% for -3 dB peak gain are obtained (C) 1999 John Wiley & Sons, Inc.