Receiving device, receiving method, and receiving system

A receiving device includes: a frequency mixer that converts a frequency of a reception signal to a baseband; an envelope demodulator; an upper sideband demodulator; and a lower sideband demodulator. Each of the envelope demodulator, the upper sideband demodulator and the lower sideband demodulator demodulates an output from the frequency mixer. The receiving device further includes: a first adder that adds an output from the envelope demodulator and an inverted output obtained by inverting an output from the upper sideband demodulator; a second adder that adds the output from the envelope demodulator and an inverted output obtained by inverting an output from the lower sideband demodulator; and a third adder that adds the output from the envelope demodulator, an inverted output obtained by inverting an output from the first adder, and an inverted output obtained by inverting an output from the second adder, to output a demodulation signal.