A digital discrete-time non-Foster approach to broadband fast-wave microstrip lines

The design of a fast-wave microstrip line is presented, where analog negative capacitance circuits are replaced by digital discrete-time non-Foster circuits. Building upon recent results for a wideband three-section fast-wave microstrip line using three negative capacitors, the proposed digital approach is shown to exhibit fast-wave characteristics over wide bandwidth with phase velocity greater than the speed of light in vacuum. Quality factor of negative capacitors is known to limit bandwidth of analog non-Foster fast-wave lines, and similar behavior is observed in the digital non-Foster simulations. Nevertheless, the proposed digital non-Foster approach is shown to offer broadband fast-wave performance, even with limited quality factor.