Dual-Functional Transmitter for Simultaneous RF/LFM Signal Using a Monolithic Integrated DFB Array

A photonics-assisted approach to dual-functional analog signal transmitter that can simultaneously generate radio-frequency (RF) signal and linear frequency modulation (LFM) signal is proposed and experimentally demonstrated. Two types of beat notes can be independently generated by heterodyning of two lasers in a photodiode using a 4-channel monolithic integrated distributed feedback (DFB) laser array. In this system, the frequency scanning for the analog signal is achieved by adding a saw-tooth signal modulating on DFB3. To the LFM signal, the center frequency and bandwidth can be tuned only by changing the direct current and the voltage of driving signal, respectively. In the experimental demonstration, the center frequency for the generated analog signal is ranging from 2 GHz to 35 GHz, limited only by the bandwidth of PD. The instantaneous bandwidth reaches to 10 GHz as well as the time-bandwidth product ~ 480,000 at the peak-to-peak voltage ~3.5 V. Dual-functional integration analog signal transmitter is possible to adapt to variable environments, with more flexible frequency tunability for multiple function and broadband bandwidth for high resolution.