Various aspects of the present disclosure involve communications, and more specifically wireless communications with modulation. As may be implemented in accordance with one or more embodiments, a rectifier having a plurality of active circuits operates in first and second modes to modulate signals communicated via an antenna as follows. The first mode is at least a half-active mode in which at least one of the active circuits passes the signal, and the second mode consumes less power than the first mode. A modulator modulates a waveform of the signal by selectively operating at least one of the plurality of active circuits, therein setting an impedance of the rectifier and modulating an amplitude of the signal.