Radar tank gauge

Claim 2

In a radar tank gauge having a focused antenna mounted in close proximity to the surface of the tank contents, for generating a continuous wave swept frequency radio frequency signal transmitted to said surface, including simultaneous measurement of a signal reflected from said surface, and generating a difference signal representative of the distance between the antenna and tank level, the improvement comprising; means generating an antenna signal of predetermined frequency and duration; means receiving a reflected signal; means deriving a signal representative of the difference between said transmitted and return signal; means measuring said difference signal in time phase synchronization with said transmitted signal; means storing groups or bins of said measured difference signals having a predetermined time duration or period; means transforming said difference signal groups from time to frequency domain, thereby generating a power spectral density representation of said difference signal; means determining the frequency centroid of said transformed signal whereby a carrier frequency closely representative of the true difference frequency is identified.

Claim 3

The improvement of claim 1 wherein said transformation utilizes at least 512 synchronized samples of at least 53.3 milliseconds duration.

Claim 4

3 . The improvement of claim 2 wherein said synchronized transmitted signal and measurement groups have integrally related periods.

Claim 5

The improvement of claim 1 wherein said antenna signal has a first swept frequency portion and a second constant frequency portion.

Claim 6

In combination; a radar tank gauge having a swept frequency signal transmitted to and reflected from the surface of the tank contents for generating a difference signal indicative of height of said tank content, and a difference signal processor comprising; means generating a transmitted radio frequency signal of predetermined period; means measuring continuous groups of said difference signal, of predetermined time; means synchronizing the periods of said transmitted and difference signal measured groups; means transforming said stored difference signals from time to frequency domain; means analyzing the power spectral density of said transformed difference signal for determining a fundamental or carrier frequency representative of the travel distance of said reflected wave.

Claim 7

In combination; a radar tank gauge having a swept frequency signal transmitted to and reflected from the surface of the tank contents for generating a difference signal indicative of height of said tank content, and a difference signal processor comprising; means generating a transmitted radio frequency signal of predetermined period; means measuring continuous groups of said difference signal, of predetermined time; means synchronizing the periods of said transmitted and difference signal measured groups; means transforming said stored difference signals from time to frequency domain; means analyzing the power spectral density of said transformed difference signal for determining a fundamental or carrier frequency representative of the travel distance of said reflected wave.

Claim 8

The difference signal processor of claim 5 wherein said measuring means comprises at least 512 groups of 53.3 milliseconds time duration.

Claim 9

The radio frequency generating means of claim 5 further comprising; means generating a time increasing voltage; a voltage controlled oscillator responsive to said voltage for transmitting a varying frequency signal; means distinguishing linear and nonlinear portions of said linearly increasing voltage; means limiting response of said voltage controlled oscillator to said linear portion of said voltage; wherein said varying oscillator frequency is restricted to the most linear portion of said generated voltage.

Claim 10

The signal processor of claim 6 wherein said transmitted signal further comprises; a swept frequency portion having a period integrally related with said measuring time; a second constant frequency period; wherein termination of any one of said measured group and initiation of said second transmitted signal period coincide.

Claim 13

The method of processing of claim 9 wherein the step of generating a transmitted signal having swept and constant frequency portion, further includes the steps of; generating a time increasing voltage having linear and nonlinear portions; generating a transmitted signal of varying frequency in response to the linear portions of said varying voltage.

Claim 14

In a radar tank gauge having a directional antenna mounted in predetermined proximity to the surface of the tank contents, for transmitting a continuous wave swept frequency radio frequency signal to said surface, said gauge including simultaneous measurement and comparison of signals transmitted to and reflected from said surface, and generating a difference signal representative of the distance between the antenna and tank level, the improvement comprising; means generating a first signal of predetermined frequency and duration; means transmitting said first signal to said surface; means receiving the reflected first signal and generating a first return signal; means generating a first signal representative of the frequency difference between said first signal and first return signal; a means measuring said first difference signal in time phase synchronization with said transmitted signal; means storing groups or bins of said measured first difference signals, said bins or groups having a predetermined time duration or period; means transforming said first difference signal groups from time to frequency domain, thereby generating a power spectral density representation of said first difference signal; means determining the frequency centroid of said transformed first signal, thereby generating a first carrier frequency value, said value closely representative of a true first difference frequency; means applying said first signal to a delay line thereby generating a second reflected signal and second return signal, said second return signal representative of a known distance; means deriving a second signal representative of the frequency difference between said first signal and second return signal; means measuring said second difference signal in time phase synchronization with said first signal; means storing said groups or bins of said measured second difference signals, said bins or groups having a predetermined time duration or period; means transforming said binned difference signal groups from time to frequency domain, thereby generating a power spectral density representation of said second difference signal; means determining the frequency centroid of said transformed second difference signal whereby a second carrier frequency closely representative of said known delay line distance is determined; means comparing said first and second carriers and generating a coefficient representative of the distance between said antenna and tank level; means applying said coefficient to said known delay line length; whereby said known delay line length is converted to said antenna/tank distance.

Claim 15

In a radar tank gauge having a directional antenna mounted in predetermined proximity to the surface of the tank contents, for transmitting a continuous wave swept frequency radio frequency signal to said surface, said gauge including simultaneous measurement and comparison of signals transmitted to and reflected from said surface, and generating a difference signal representative of the distance between the antenna and tank level, the improvement comprising; means generating a first signal of predetermined frequency and duration; means transmitting said first signal to said surface; means receiving the reflected first signal and generating a first return signal; means generating a first signal representative of the frequency difference between said first signal and first return signal; a means measuring said first difference signal in time phase synchronization with said transmitted signal; means storing groups or bins of said measured first difference signals, said bins or groups having a predetermined time duration or period; means transforming said first difference signal groups from time to frequency domain, thereby generating a power spectral density representation of said first difference signal; means determining the frequency centroid of said transformed first signal, thereby generating a first carrier frequency value, said value closely representative of a true first difference frequency; means applying said first signal to a delay line thereby generating a second reflected signal and second return signal, said second return signal representative of a known distance; means deriving a second signal representative of the frequency difference between said first signal and second return signal; means measuring said second difference signal in time phase synchronization with said first signal; means storing said groups or bins of said measured second difference signals, said bins or groups having a predetermined time duration or period; means transforming said binned difference signal groups from time to frequency domain, thereby generating a power spectral density representation of said second difference signal; means determining the frequency centroid of said transformed second difference signal whereby a second carrier frequency closely representative of said known delay line distance is determined; means comparing said first and second carriers and generating a coefficient representative of the distance between said antenna and tank level; means applying said coefficient to said known delay line length; whereby said known delay line length is converted to said antenna/tank distance.

Claim 16

The improvement of claim 11 further comprising; means storing a predetermined value of said coefficient, said coefficient representing a predetermined limit of said antenna/tank level distance; means comparing said stored and antenna/surface distances; whereby coefficients greater than said stored value are disregarded.