Generation of Millimeter-Wave Ultra-Wideband Pulses Free of Strong Local Oscillation and Background

A novel scheme of generating millimeter-wave (MMW) ultra-wideband (UWB) pulses free of strong local oscillation (LO) and background is proposed and demonstrated. The frequency of the optical Gaussian pulses is first up-converted by a Mach-Zehnder modulator, which is biased at its minimum transmission point to achieve carrier suppression modulation. Then, the up-converted Gaussian pulses are equally split into two parts with a relative time delay. At last, the two parts are injected into the two arms of a balanced photodetector (BPD) respectively. After the BPD, the low-frequency components are effectively suppressed and MMW-UWB pulses free of background and strong LO are generated. The polarity of generated MMW-UWB can be converted by adjusting the relative time delay between the two parts. In the experiment, a pair of polarity-reversed background-free UWB pulses centered at 25 GHz is successfully generated. The 10-dB bandwidth of the MMW-UWB spectra is 4.14 and 4.05 GHz, respectively.