This paper presents a technique for extending the bandwidth of chirped active sonar signals. Bandwidth synthesis (BWS) results in improved range resolution, increased signal-to-noise ratio (SNR) and reduced fading due to delay-spread multipath. The approach demonstrated uses a low-order autoregressive (AR) process to model de-chirped segments of the received signal, which are then extrapolated using linear prediction (LP). Both simulated results and an initial sea trial result confirms BWS performance.