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.