Moreover, a 4-port dual directional-coupler is used as a personator of balanced device to verify mathematical balun theory. Good agreement of results with that of Agilent equipment is observed and the mathematical balun theory is proved effective. 此外,用四端口双定向耦合器作为待测器件验证了数学巴伦法的理论,结果与Agilent仪器的测量结果符合很好,说明了这种数学巴伦理论的正确性。