Multi-level digital modulation performed directly at carrier frequency

Direct modulation of the carrier signal has been shown to be an attractive means of reducing the complexity of the RF hardware required in a communications transceiver. To this end, a proof-of concept X-band vector modulator, realised using monolithic phase shifters and attenuators, has been used to demonstrate that multi-level digital modulation can be implemented at high data rates and without requiring significant control power. The measured constellations for QPSK, 32-PSK and 16 QAM modulation are presented. This technique is suitable for both microwave and millimetre wave appicatons.