A Digitized IF-Over-Fiber Transmission Based on Low-Pass Delta-Sigma Modulation

In this letter, we propose and demonstrate a digitized intermediate frequency (IF)-over-fiber transmission system based on the delta-sigma modulation technique as a means of digitizing an analog IF signal. Using a realized 130-nm CMOS, two-level third-order low-pass delta-sigma modulator (DSM) chip operating at 622.08 MHz, a 64-Quadrature Amplitude Modulation long-term evolution (LTE) 10-MHz signal at a 10-MHz IF frequency was successfully digitized, transported over an emulated digital fiber-optic link, and analyzed in terms of signal spectra, error vector magnitude (EVM), and constellations. The difference between power levels of the received LTE IF signal and quantization noise due to the developed DSM was larger than 45 dB, and an EVM value of 2.48% for the received LTE signal was obtained.