Continuous-wave reflection transmissometer with target discrimination using modulated targets
First Claim
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1. A method for measuring the attenuation of electromagnetic radiation along a transmission path through a propagation medium under conditions of unknown attenuation, said method comprising:
- (a) positioning an antenna, a transmitter and a receiver at one end of the transmission path many wavelengths long;
(b) positioning an electromagnetic energy reflector at the other end of the transmission path;
(c) radiating continuously a periodic, continuous electromagnetic wave from the antenna toward said reflector;
(d) periodically modulating the reflection properties of the electromagnetic energy reflector to thereby modulate the incident periodic, electromagnetic waves;
(e) receiving the wave reflected from the reflector;
(f) detecting a signal which is monotonically related to the power of the received modulated reflected wave;
(g) performing steps (a) through (f) under conditions of know attenuation; and
(h) comparing the signals detected in step (f) under conditions of unknown attenuation and step (g) under conditions of known attenuation to determine the relative attenuation.
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Abstract
The attenuation of electromagnetic waves by a transmission medium is detected or measured by directing a continuous periodic electromagnetic wave toward a reflector. The reflector is modulated to modulate the electromagnetic wave as it is reflected. The reflected wave is received and an output signal related monotonically to the power of the modulated reflected wave is detected. The output signal is then compared to the output signal which is or would be obtained under various other transmission conditions.
49 Citations
18 Claims
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1. A method for measuring the attenuation of electromagnetic radiation along a transmission path through a propagation medium under conditions of unknown attenuation, said method comprising:
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(a) positioning an antenna, a transmitter and a receiver at one end of the transmission path many wavelengths long; (b) positioning an electromagnetic energy reflector at the other end of the transmission path; (c) radiating continuously a periodic, continuous electromagnetic wave from the antenna toward said reflector; (d) periodically modulating the reflection properties of the electromagnetic energy reflector to thereby modulate the incident periodic, electromagnetic waves; (e) receiving the wave reflected from the reflector; (f) detecting a signal which is monotonically related to the power of the received modulated reflected wave; (g) performing steps (a) through (f) under conditions of know attenuation; and (h) comparing the signals detected in step (f) under conditions of unknown attenuation and step (g) under conditions of known attenuation to determine the relative attenuation. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
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14. A reflection transmissometer for detecting the attenuation of electromagnetic radiation through a propagation medium at a selected frequency, said transmissometer comprising:
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(a) a transmitter for radiating continuously a periodic, continuous, electromagnetic wave at the selected frequency; (b) an electromagnetic energy reflector in the path of the radiated wave, substantially larger than a wavelength of said transmitted wave, spaced at least many wavelengths from the transmitter and oriented to reflect a portion of the radiated wave, said reflector including a modulator for periodically modulating the reflection properties of the reflector and thereby causing the reflected wave to be modulated; and (c) a receiver positioned to receive the reflected wave for detecting a signal related monotonically to the power of the received, modulated wave. - View Dependent Claims (15, 16, 17, 18)
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Specification