An implementation of the chirp transform algorithm for performing a real‐time Fourier transform is described. The implementation is based upon an acousto‐optic convolver with a large time‐bandwidth product An instantaneous bandwidth of about 75 MHz was achieved for the Fourier transformer with a dynamic range in excess of 60 dB for a cw time‐gated waveform. By using an almost‐uniform light‐beam intensity across the device, the measured sidelobe amplitudes were within 0.5 dB of the theoretical values. The corresponding measured phase errors were less than 5°. The adaptability of this acousto‐optic implementation is demonstrated by the ease with which one can vary both the sidelobe weighting function and the time rate of the transform.