  This paper experimentally evaluates the Generalized Sinusoidal Frequency
Modulated (GSFM) waveform, a generalization of the Sinusoidal Frequency
Modulated (SFM) waveform. The Instantaneous Frequency (IF) of the GSFM
resembles the time/voltage characteristic of a Linear FM (LFM) chirp waveform.
Consequently, the GSFM possesses an Ambiguity Function (AF) that resembles a
thumbtack shape. Practical sonar system design must consider two factors beyond
the AF. The spectral efficiency (SE), defined as the ratio of energy in an
operational frequency band to the total waveform energy, is another important
metric for waveform design. The Peak-to-Average-Power Ratio (PAPR) quantifies
how close the waveform is to constant amplitude. These measures predict a
waveform's energy efficiency and ability to be accurately replicated on
practical piezoelectric transducers, which have limits on both their bandwidth
and maximum transmit power. This paper explores these design considerations for
the GSFM waveform and evaluates its performance against a host of other well
established waveforms using simulated and experimental acoustic data. The GSFM
possesses superior SE, PAPR, and overall energy efficiency when compared to
thumbtack waveforms.
