Dual-Polarized Annular Ring Patch Antenna for 2.4 GHz Doppler Radar
Doppler radar sensing of heart and respiration rates is a promising technique for healthcare applications. Typically, Doppler radar transmits a Continuous-Wave (CW) signal and demodulates the signal reflected off a target. According to Doppler theory, a human chest wall that has a periodic time-varying position will reflect the phase-modulated signal in proportion to the position of the chest wall. By demodulating this phase modulated signal, the heart and respiration rates can be obtained. Because Doppler radars transmit and receive a signal at the same time and at the same frequency, good isolation between the Transmitter (TX) and Receiver (RX) circuit is very important for the proper detection of weak vital signals.