BROADSIDE RADIATION FROM PERIODIC LEAKY-WAVE ANTENNAS

A double-strip grating leaky-wave antenna, consisting of two strips per unit cell, is analyzed. By properly placing the two metal strips within the unit cell, the stop-band behavior exhibited at broadside scan in the single-strip grating antenna may be significantly reduced, and almost eliminated. This stop-band behavior is characteristic of all periodic leaky-wave antennas having a single strip per unit cell, and results in a drastic increase in the attenuation rate of the leaky wave as the beam is scanned to broadside. By nearly eliminating this stop-band behavior, the double-strip leaky-wave antenna is able to scan from backward end fire to forward end fire without any large frequency regions of high attenuation. An approximate design rule for the double-strip antenna is discussed, and results are presented to show how the antenna may be further optimized to achieve the minimum possible variation in attenuation as the beam is scanned through broadside. Although the stop-band behavior is never completely eliminated with the addition of the extra strip, the optimum design shows an almost negligible region of rapidly varying attenuation near broadside.