body. pre-amplifier and then mixed person’s The large clutter from the rubble with a local reference signal in can be cancelled by a clutter a double balanced mixer. canceling signal . Three-fourth of the output is The small reflected wave from the directed by a microwave detector body cannot be cancelled to provide a DC output, which person’s by a pure sinusoidal canceling serves as the indicator for the because it is modulated by their degree of the clutter cancellation . movements. When the settings of the digitally The output of the clutter controlled phase shifter and the cancellation circuit is attenuator are swept the automatically adjusted to be of microprocessor control system, equal amplitude and opposite the output of the microwave phase as that of the clutter from detector varies accordingly. the rubble . DEMODULATION OF THE Thus, when the output of the CLUTTER CANCELLED SIGNAL: clutter cancellation circuit is At the double balanced mixer, the combined with the directional amplified signal of the reflected coupler3 ( 3 dB ), the large clutter wave from the body is person’s from the rubble is completely cancelled mixed with the local reference Now, the output of the directional signal. coupler3 (3dB) is passed The phase of the local reference through a directional coupler4 signal is controlled by another (6dB) digitally controlled phase One-fourth of the output is shifter2 for an optimal output directed is amplified by a RF from the mixer.
person’s body. The large clutter from the rubble can be cancelled by a clutter canceling signal . The small reflected wave from the person’s body cannot be cancelled by a pure sinusoidal canceling because it is modulated by their movements. The output of the clutter cancellation circuit is automatically adjusted to be of equal amplitude and opposite phase as that of the clutter from the rubble . Thus, when the output of the clutter cancellation circuit is combined with the directional coupler3 ( 3 dB ), the large clutter from the rubble is completely cancelled Now, the output of the directional coupler3 (3dB) is passed through a directional coupler4 (6dB) One-fourth of the output is directed is amplified by a RF pre-amplifier and then mixed with a local reference signal in a double balanced mixer. Three-fourth of the output is directed by a microwave detector to provide a DC output, which serves as the indicator for the degree of the clutter cancellation . When the settings of the digitally controlled phase shifter and the attenuator are swept the microprocessor control system, the output of the microwave detector varies accordingly. DEMODULATION OF THE CLUTTER CANCELLED SIGNAL: At the double balanced mixer, the amplified signal of the reflected wave from the person’s body is mixed with the local reference signal. The phase of the local reference signal is controlled by another digitally controlled phase shifter2 for an optimal output from the mixer.
217172596-Embedded-System-life-Saving-Us.docx