Ultra-wideband doublet signal generation with tunable notch band based on delay-line filter

Abstract

ABSTRACT A novel and simple scheme to generate Ultra-wideband (UWB) doublet signal with tunable notch band based on a tunable delay-line filter is presented. The first-order differentiation is realized by a dual-drive Mach–Zehnder modulator (DD-MZM), which differentiates the Gaussian pulses to the monocycle pulses. Subsequently, the UWB monocycle pulses are transmitted to an optical delay-line filter implemented by a balanced photo-detector and a tunable delay line for both differentiation and photodetection. Consequently, the desired UWB doublet signal can be obtained with a 10-dB bandwidth of 8.75 GHz. Besides, the polarity reversibility of the generated doublet signal is demonstrated by changing the bias voltage of the DD-MZM. Moreover, the desired notch can be introduced in the generated frequency spectrum to eliminate the interference between the existing narrowband systems and the UWB systems. And the tunability of the band-notched position is implemented by simply adjusting the delay time of the delay-line filter. The feasibility of the presented scheme is investigated by mathematical models and simulations.