Low-OSR asynchronous Σ-Δ modulation high-order buck converter for efficient wideband switching amplification

This work explores two methods to time-encode continuous- time wideband signals, namely asynchronous Sigma-Delta and PWM, targeting modulating methods for buck-based switching power converters operating as wideband power amplifiers. In applications such as polar transmitters or line drivers for Power Line Communications, whose aim is bounding the overall losses, there exists a trade-off involving tracking error and OverSampling Ratio (OSR). This work characterises and compares, in terms of tracking error, the complete design space of modulation depth, OSR and filter cutoff frequency for each encoding method. Moreover, it also characterises an additional dimension in the design space, the effect of using a high-order buck converter. The results from this comparison point-out that low-OSR combined with high-order buck converters, are good candidates to address the challenge of wideband high-efficiency amplifiers.