| 摘要 |
<p>A microwave oscillator (11-18) used in a microwave proximity sensor employs a 1/2- or 1/4- wavelength folded dipole antenna (10) both as a resonant-frequency-determining element and as a transmitting/receiving antenna. A capacitor (20) is charged until it reaches a sufficient voltage to trigger the operation of the oscillation (11-18), then powers the oscillator till the voltage drops so low oscillation ceases, then begins charging again. A negative peak follower (33-36) converts the lowest voltage across the capacitor (20) to a D.C. voltage. A comparator (39-45) detects changes in the output voltage of the peak follower (33-36), which indicate approach by a person or object to the antenna (10). Power consumption is much lower than with the conventional approach of monitoring total power consumption.</p> |
