| 摘要 |
<p>@ An intrusion detector system with a transmitter (Figure 1) having a transmitter clock (22, 24, 26) operating at a selected frequency, with the frequency being one of a selected number of frequencies, a pseudorandom code sequence generator (28) for generating one of a selected number of codes, a modulator (42, 20) for spread-spectrum modulating an electromagnetic signal with the generated pseudorandom code sequence signal, and a transmitter antenna (36) for transmitting the modulated signal through a zone of protection; and a receiver (Figure 2) having a receiving antenna (38) a demodulator for detecting and demodulating the modulated signal to recover the transmitter pseudorandom code sequence signal, a receiver clock (64, 66, 68) operating at a frequency corresponding to the transmitter clock, with the frequency being one of a selected number of frequencies, a pseudorandom code sequence generator (70) for generating one of a selected number of receiver pseudorandom code signals corresponding to the transmitter pseudorandom code sequence signals, a detector (58) for comparing the received transmitter code sequence signal to the receiver code signal and generating a detection signal proportional to the signal amplitude of the received code signal when locked in phase with the receiver code signal, a phase detector (60) for detecting the phase difference between the two code signals, a control for phase synchronizing the two code signals, and a monitor (80) for detecting changes in the detection signal resulting from entry of movement of an intruder in the zone of protection and for generating a signal in response thereto.</p> |
