An RF front-end circuit of an RF transceiver is described herein. In accordance with one exemplary embodiment, the fronted circuit includes a local oscillator (LO) configured to generate an RF transmit signal, an RF output port coupled to the local oscillator, wherein the RF transmit signal is output at the RF output port, and a monitoring circuit receiving an input signal and configured to determine the phase of the input signal or the power of the input signal or both. A directional coupler is coupled to the RF output port and configured to direct a reflected signal incoming at the RF output port as input signal to the monitoring circuit, and a controller is configured to detect, based on the determined phase or power or both, a defect in a signal path operably connected to the RF output port.