K-band Mixerless Transmitter Using a Graphene MMIC Process on Flexible Substrate

A <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$K$</tex>-band mixerless transmitter (Tx) on flexible substrate using a graphene MMIC process has been designed and presented in this paper. The novel mixerless transmitter configuration has to be employed to support complex modulated signal, i.e. QAM, due to the limitation of the current graphene process. The Tx is composed of an input phase distribution network, an impedance modulation network, and a power combiner network. It means that branch-line couplers, Wilkinson power dividers, and Metal-insulator-graphene (MIG) diodes as a voltage-controlled impedance modulation network are used. The <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$S$</tex>-parameters of the MIG diodes with different biasing voltages have been measured and used for the Tx simulation. Simulated <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\text{EVM}_{\mathrm{r}\mathrm{m}\mathrm{s}}$</tex> of 4.3% and <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\text{EVM}_{\text{peak}}$</tex> of 7.7% are observed for 16-QAM signal at 18 GHz.