Semiconductor chip with local oscillator buffer reused for loop-back test and associated loop-back test method

A semiconductor chip comprising:

• a first wireless communication circuit, comprising a signal path, wherein the signal path comprises a mixer input port and a signal node distinct from the mixer input port, and further comprises a balanced-to-unbalanced (balun) circuit;
• and the signal node is an ungrounded terminal on an unbalanced side of the balun circuit;
• a local oscillator (LO) buffer, arranged to receive and buffer an LO signal;
• and
• an auxiliary path, arranged to electrically connect the LO buffer to the signal node of the signal path, wherein the LO buffer is reused for a loop-back test function of the first wireless communication circuit through the auxiliary path.