The apparatus comprises a first coupler configured to receive two output signals, having 180° phase difference, outputted from a first differential generator as two input signals, and output a first voltage signal generated by adding the two input signals and a second voltage signal corresponding to subtraction of the two input signals, a second coupler configured to receive two output signals, having 180° phase difference, outputted from a second differential generator as two input signals, and output a third voltage signal generated by adding the two input signals and a fourth voltage signal corresponding to subtraction of the two input signals, a coupling network connected to the first differential generator and the second differential generator and a third coupler configured to output a signal generated by adding the voltage signal outputted from the first coupler and corresponding voltage signal outputted from the second coupler.

The apparatus comprises a first coupler configured to receive two output signals, having 180 phase difference, outputted from a first differential generator as two input signals, and output a first voltage signal generated by adding the two input signals and a second voltage signal corresponding to subtraction of the two input signals, a second coupler configured to receive two output signals, having 180 phase difference, outputted from a second differential generator as two input signals, and output a third voltage signal generated by adding the two input signals and a fourth voltage signal corresponding to subtraction of the two input signals, a coupling network connected to the first differential generator and the second differential generator and a third coupler configured to output a signal generated by adding the voltage signal outputted from the first coupler and corresponding voltage signal outputted from the second coupler.

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.

A splitter/combiner having a first port, a second port, and a third port includes a first transmission line coupled between the first port and the second port, a second transmission line coupled between the first port and the third port, a resistor coupled between the second port and the third port, and first and second capacitors each having a first terminal and a second terminal, the first terminal of the first capacitor coupled to the second port, the first terminal of the second capacitor coupled to the third port, the second terminal of each of the first and second capacitors coupled to a common node. At least one of the first capacitor, second capacitor, first transmission line, and second transmission line is adjustable during operation for varying the electrical properties of the splitter/combiner.