Towards a design of the ultra-wideband microwave devices using the non-foster negative reactances

A novel simple and efficient approach to a design of the ultra-wideband (UWB) microwave devices using the non-Foster negative reactances implemented as the transistor negative impedance converters is presented. Series as well as parallel connection of the positive inductance and negative capacitance (or vice versa) allows providing the sum reactance with only a small variation over a wide frequency band. The beneficial applications of such quasi-constant reactances to a design of the UWB directional coupler and bandpass filter as well as the triple-bandpass filter for WLAN are demonstrated.