Frequency conversion circuit for time division duplex system

The invention relates to a frequency conversion circuit for a time division duplex (TDD) system. The frequency conversion circuit has a first transmitting end, a first receiving end, a second receiving end, a first transmitting input end, a first receiving output end and a second receiving output end. The frequency conversion circuit comprises a first mixer, a first single-pole double-throw switch, a second single-pole double-throw switch and a second mixer. The first single-pole double-throw switch and the second single-pole double-throw switch are respectively connected at a first end and a second end of the first mixer. The first transmitting end and the first transmitting input end are respectively connected with the first end of the first single-pole double-throw switch and the first end of the second single-pole double-throw switch. The first receiving end and the first receiving output end are respectively connected with the second end of the first single-pole double-throw switch and the second end of the second single-pole double-throw switch.