Nearly all IoT devices require wireless connectivity, and to keep costs down and deployment opportunities up, communication should ideally occur with widely deployed commodity hardware such as WiFi. However, conventional WiFi transceivers (TRXs) require 10s to 100s of mW of active power. As a result, nearly all current WiFi-compatible IoT devices require either wall power, or large/frequently re-charged batteries (Fig. 20.1.1, left). While other standards such as BLE may require less power, very low power (<<1mW) is only achievable at very low throughputs via duty-cycling; and yet, despite low average power, very small coin cell batteries or energy harvesters cannot be used due to still relatively high peak-power requirements (e.g., a few mW for BLE), thereby limiting new products to certain minimum device sizes. More importantly, standards such as BLE do not have widely distributed infrastructure in most homes, offices, or other environments, making rapid low-cost deployment difficult. To enable a new class of miniaturized, battery-powered or energy-harvested IoT devices, backscatter communication, where an incident RF source is reflected via a low-power impedance modulating tag, has been proposed.