  Quadrature amplitude modulation (QAM) exhibits a shaping-loss of $\pi
\mathrm{e}/6$, ($\approx1.53$ dB) compared to the AWGN Shannon capacity. With
inspiration gained from special (leaf, flower petal, and seed) packing
arrangements (spiral phyllotaxis) found among plants, a novel, shape-versatile,
circular symmetric, modulation scheme, the Golden Angle Modulation (GAM) is
introduced. Disc-shaped, and complex Gaussian approximating bell-shaped,
GAM-signal constellations are considered. For bell-GAM, a high-rate
approximation, and a mutual information optimization formulation, are
developed. Bell-GAM overcomes the asymptotic shaping-loss seen in QAM, and
offers Shannon capacity approaching performance. Transmitter resource limited
links, such as space probe-to-earth, and mobile-to-basestation, are cases where
GAM could be particularly valuable.
