Measurement of a fast-wave line using digital non-Foster circuits for software-adjustable delay

Measured results are compared to simulation results for a wideband software-adjustable fast-wave line using coaxial line sections loaded with digital discrete-time non-Foster circuit elements. In the proposed approach, the negative capacitance of non-Foster circuit elements is varied by changing the signal processing in the digital non-Foster circuit. For the purposes of demonstration and comparison with analog non-Foster approaches, a prototype three-stage fast-wave coaxial line is implemented using three digital negative capacitors. Group delay is shown to be less than in corresponding vacuum propagation, and group delay is shown to be adjustable in software with varied negative capacitance. Measured and simulated results are in good agreement, and closely resemble a frequency-scaled version of prior fast-wave results for analog non-Foster loaded waveguide at higher frequency.