Back to results
US 7,078,913 B1Granted
Multipath resistant microwave moisture sensor
AssigneeThe United States of America as represented by the Secretary of Agriculture
InventorMathew G. Pelletier
Life of this patent
Estimating the term…
Abstract
The moisture content of a test material may be determined using a microwave-based process and device which is free from interference by multipath standing waves. Multipath signals may be electronically removed from the measured signal.
Claims25
A process for determining the moisture content of a material comprising:
- producing a primary microwave signal with a varying frequency, said signal being a continuously varying signal or a discrete time varying signal,
- splitting said primary signal to provide first and second microwave signals, said first signal to be transmitted through said material and said second signal comprising an internal reference signal,
- transmitting said first signal through at least a portion of said material,
- receiving at a receiver a third signal which comprises potential multi-path interference signals and said first signal which has passed through said material,
- mixing said third signal together with said second signal, generating a mixed signal,
- filtering said mixed signal to remove substantially all of said multi-path interference signals, generating a filtered-mixed signal
- measuring the frequency of said filtered-mixed signal to determine the propagation delay of said first signal after it has passed through said material, and
- calculating the moisture content of said material from said propagation delay of said first signal after it has passed through said material,
- wherein the frequency of said primary signal varies sufficiently rapidly that the frequency of said third signal and said second signal will be different when they are received at said receiver.
6 more elements
An apparatus for automatically determining the moisture content of a material comprising:
- a microwave signal generator effective for producing a microwave signal with either a continuously varying frequency or a discrete time varying frequency,
- a microwave signal transmitter effective to transmit said microwave signal through the material,
- a microwave signal receiver effective to receive said microwave signal after it has passed through said material,
- a microwave signal mixer effective for mixing said microwave signal received by said receiver and a reference signal to generate a mixed signal,
- a microwave signal filter effective to remove substantially all multipath interference signals to generate a filtered-mixed signal, and
- a frequency detector effective to determine the frequency of said filtered-mixed signal,
- wherein the frequency of said primary signal varies sufficiently rapidly that the frequency of said third signal and said second signal will be different when they are received at said receiver.
4 more elements
Dependencies are inferred from the claim text.