專利摘要：
A reflective modulator comprises a coupler, two diodes and two DC block units. The coupler has an input end used to output an output signal, an output end used to output an output signal, a first load end connected to one of the diodes and a second load end connected to another one of the diodes. The DC block units connect between the diodes and the coupler for DC blocking. A message signal is selectively inputted to both of the two DC block units for operating the state of the two diodes. A BPSK modulator using the reflective modulator and a quadrature modulator using the BPSK modulator are also introduced.