Energy optimisation of an On-Off Keying (OOK) transmitter using high-order orthogonal modulation

ABSTRACT In this paper, we show that high-order orthogonal modulation can be used to optimise the power consumption of an energy-efficient On-Off Keying (OOK) transmitter for short-range wireless sensor applications. Our work is based on the characteristics of a high-performance OOK modulator that completely turns off during the transmission of zeros and provides energies per bit in the picojoule range. We take into account the limitations of the circuit in terms of maximum modulation rate and constant output power. Based on a bit error rate performance analysis and a circuit energy model, we propose an original approach to find the energy optimal modulation order for a given range constraint. When considering only the transmitter power consumption, a large improvement in energy per bit can be obtained by using this optimisation. When considering a residual power consumption during the transmitter off state, an improvement is still obtained but is less important.