Two-Dimensional Beamforming with Nonsinusoidal Signals

A two-dimensional beamforming technique is presented for two-dimensional arrays of (N × N) sensors receiving plane wavefronts with nonsinusoidal time variations in the form of a single rectangular pulse of duration T or in the form of a coded sequence of rectangular pulses with nominal time duration T. The three-dimensional energy pattern has a main beam for small angles of incidence and a number of sidelobes for large angles of incidence. For wavefronts with rectangular time variations, the maximum sidelobe has the magnitude 1/N and, for coded time variations, the maximum sidelobe exceeds 1/N. The magnitude of the sidelobes of the energy pattern can be decreased by increasing the number of sensors in the array. The resolution angle can be decreased by the ratio (N1/N2) when the number of sensors is increased from (N1 × N1) to (N2 × N2) and it can be decreased by the ratio (T1/T2) when the nominal time duration is decreased from T2 to T1. Waveform distortion results in a degradation of the resolution angle.