Isolator

An isolator, comprising:

• a first frequency mixer;
• a second frequency mixer;
• a local oscillator;
• a phase delayer;
• and
• a phase shifter, wherein
• the first frequency mixer and the second frequency mixer are connected in series,
• the local oscillator is connected to the first frequency mixer and the second frequency mixer and is configured to input a local signal with a same frequency to the first frequency mixer and the second frequency mixer,
• a signal targeted for isolation is input to the first frequency mixer,
• a frequency of the signal input to the first frequency mixer is up-converted by the local signal,
• the second frequency mixer receives the up-converted signal via the phase delayer, a frequency of the up-converted signal is down-converted, and the down-converted signal is output from the second frequency mixer,
• the phase delayer is configured to delay a phase of the up-converted signal,
• the phase shifter is configured to convert a phase of the local signal received from a divider to cause a phase difference between the first frequency mixer and the second frequency mixer,
• an amount of phase delay of the signal with the delayed phase and the phase difference is defined by the following equations (A) and (B), and
• wherein further ϕup0 (degree) in the equation (A) and ϕLO0 (degree) in the equation (B) is set so as a gain of a progressive wave that moves in a direction of a signal transmission to be larger than a gain of a regressive wave that moves in an opposite direction to the direction of the signal transmission,
• ϕup (degree)=ϕup0 (degree)+180 (degree)×n Equation (A)
• ϕup (degree):
• amount of phase delay
• n:
• integer
• ϕLO (degree)=ϕLO0 (degree)+180 (degree)×m Equation:
• (B)
• ϕLO (degree):
• phase difference
• m:
• integer.