An integrated non-contact vital sign detector for handheld applications is demonstrated. The detector includes a radio frequency transceiver, baseband analog circuits, and a baseband signal processor. The RF transceiver transmits a continuous RF signal toward the subject and receives the reflected signal. The direct conversion receiver chain downconverts the received signal to baseband and the baseband analog circuit further amplifies and level-shifts the output. The signal processor performs spectrum analysis on the baseband signal. The baseband signal processor is realized by an ARM7TDMI microprocessor. Key algorithm of the spectrum analysis is described in detail. Experiments were performed with two subjects, a human subject and an actuator moving in two-tone motion. Results were analyzed to verify the accuracy of the detection. The guideline on selecting sampling frequency for different applications is described.