Bandwidth Enhancement of a Series-Fed Microstrip Patch Array Antenna

A design method for wideband series-fed microstrip patch array antenna is proposed. The long-line effect which is the factor of narrowing the bandwidth of the series-feed method is reduced by utilizing the phase change due to the reflection. The line impedance of the series-feed circuit including the element antennas is optimized by the circuit simulator incorporating the automatic convergence calculation function. The designed 18-element array antenna can obtain nearly uniform phase distribution even though the frequency changes. The gain bandwidth of the fabricated antenna is increased compared with the antenna designed by the conventional method.