A 10.24GSPS photonic sampled bandpass /spl Delta//spl Sigma/ modulator direct-sampling at 12GHz
A 10.24GSPS photonic sampled DeltaSigma modulator was implemented with HRL laboratories InP HBT process. The 12GHz analog input is sampled by a LiNbO3 optical modulator with a 10.24GHz ultra-low jitter mode-locked laser. The intensity-modulated differential laser pulses are converted into electronic charges by on-chip GaInAs photo diodes and directly integrated into the first stage integrator of a 4th-order continuous-time bandpass DeltaSigma modulator with a passband centered at 1.8GHz. The high notch frequencies of the DeltaSigma ADC are achieved by using a special type of integrator. This ADC achieves 59.9dB SNDR in 1MH bandwidth with 1263 InP HBT transistors