A quasi-circulator using an asymmetric directional coupler , wherein the directional coupler includes: a first transmission line disposed to have an impedance value of Z1 in which a transmitter connection terminal is formed at one end and an antenna connection terminal is formed at the other end; a second transmission line disposed to have an impedance value of Z3 disposed to be spaced apart from the first transmission line by a predetermined interval, in which a receiver connection terminal is formed at one end and a high frequency resistor connection terminal is formed at the other end; a first coupling line disposed to have an impedance value of Z2 vertically connected with the first transmission line , in which the second transmission line is configured such that a transmitting signal from the transmitter connection terminal is partially extracted and coupled to the receiver connection terminal ; and a second coupling line disposed to have an impedance value of Z4 vertically connected with the first transmission line and the second transmission line , from which the transmitting signal from the transmitter connection terminal is configured to be electrically isolated, and wherein the impedances of the first transmission line , the second transmission line , the first coupling line , and the second coupling line are arranged to have different values configured to isolate the transmitting signal from a receiving signal such that a quasi-circulator function is implemented, wherein each impedance value is estimated by using a design parameter equation, wherein the design parameter equation is |k • m | = 1, wherein k is the transmittance ratio from the impedance difference between Z1 and Z3 and m is a ratio of the reflection coefficient at the high frequency resistor connection terminal over the reflection coefficient of a matched high frequency resistor. a first transmission line disposed to have an impedance value of Z1 in which a transmitter connection terminal is formed at one end and an antenna connection terminal is formed at the other end; a second transmission line disposed to have an impedance value of Z3 disposed to be spaced apart from the first transmission line by a predetermined interval, in which a receiver connection terminal is formed at one end and a high frequency resistor connection terminal is formed at the other end; a first coupling line disposed to have an impedance value of Z2 vertically connected with the first transmission line , in which the second transmission line is configured such that a transmitting signal from the transmitter connection terminal is partially extracted and coupled to the receiver connection terminal ; and a second coupling line disposed to have an impedance value of Z4 vertically connected with the first transmission line and the second transmission line , from which the transmitting signal from the transmitter connection terminal is configured to be electrically isolated, and wherein the impedances of the first transmission line , the second transmission line , the first coupling line , and the second coupling line are arranged to have different values configured to isolate the transmitting signal from a receiving signal such that a quasi-circulator function is implemented, wherein each impedance value is estimated by using a design parameter equation, wherein the design parameter equation is |k • m | = 1, wherein k is the transmittance ratio from the impedance difference between Z1 and Z3 and m is a ratio of the reflection coefficient at the high frequency resistor connection terminal over the reflection coefficient of a matched high frequency resistor. <EOS>