Neural networks recently gained attention as fast and flexible vehicles to
microwave modeling, simulation, and optimization. After learning and abstra
cting from micron ave data, through a process called training, neural netwo
rk models are used during microwave design to provide instant answers to th
e task learned. Appropriate neural network structure and suitable training
algorithm are two of the major issues in developing neural network models f
or microwave applications. Together. they decide amount of training data re
quired, accuracy that could possibly be achieved, and more importantly deve
lopmental cost of neural models. A review of the current status of this eme
rging technology is presented, with emphasis on neural network structures a
nd training algorithms suitable for micron ave applications. Present challe
nges and future directions of the area are discussed. (C) 1999 John Wiley &
Sons, Inc.