Аннотация:In design of direct conversion apparatus a mixer on opposite-parallel diodes is used widely. However in the published works wrong conclusions are given in respect to mixer parameters and its operation regime choice because these conclusions are based on application of a switching regime model. New theoretical analysis of mixer operation on opposite-parallel diodes in regime of synchronous detection is carried out. The made calculations show that a multi-band receiver with such the mixer can be designed in the case of large enough amplitudes of a heterodyne.