Real time threshold

Claim 2

Means for detecting the envelope of a radiated beam scanning through space at a receiver illuminated by the beam wherein the receiver includes circuits for producing the envelope of said beam, comprising: means for generating a signal at a signal level related to a predetermined point on said envelope and comprising a peak detector for detecting the peak level of said envelope and summing means decreasing the detected peak level by a predetermined amount to generate said signal level; analog means for delaying said envelope a predetermined time; and, means for thresholding the delayed envelope in accordance with said signal level.

Claim 3

The means for detecting of claim 1 wherein said radiated beam includes a sub-carrier whose frequency varies in relation to the departure of the beam from a predetermined line or plane in space, and wherein said receiver includes means for demodulating the sub-carrier, said means for detecting additionally comprising second means for delaying the demodulated sub-carrier by the same time as said analog means delays said envelope.

Claim 4

The means for detecting of claim 2 wherein said second means for delaying comprises: means for detecting the zero crossings of said demodulated sub-carrier; and, means for delaying the detected zero crossings by the same predetermined time as said envelope is delayed.

Claim 5

Means for detecting as recited in claim 3 wherein said beam is radiated from a fixed station and scanned from a predetermined position at a constant angular speed to a second predetermined position in one cycle so as to illuminate said receiver once in each cycle, and wherein said means for thresholding comprises: means for generating a threshold signal in response to said signal level and displaced a predetermined amount therefrom; means responsive to said threshold signal for generating a first gate signal during the time said envelope exceeds said threshold signal; means for generating a precision gate signal extending from the occurrence of the first zero crossing in a predetermined direction after the beginning of said first gate signal and extending to the occurrence of the first zero crossing in a predetermined direction after the end of said first gate signal; means for determining the duration of said percision gate signal; means for counting the number of zero crossings occurring during the duration of said precision gate signal; and, means for dividing the number counted by said means for counting by the duration determined by said means for determining.

Claim 6

Means for detecting the envelope of a radiated beam scanning through space at a receiver illuminated by the beam wherein the receiver includes circuits for producing the envelope of said beam and wherein said beam is radiated from a fixed station and scanned in one cycle from a predetermined position at a constant angular speed to a second predetermined position and return so that said receiver is illuminated twice by said beam during one cycle, comprising: means for generating a signal at a signal level related to a predetermined point on said envelope; analog means for delaying said envelope a predetermined time; means for generating a threshold signal in response to said signal level and displaced a predetermined amount therefrom; means responsive to said threshold signal for generating a gate signal during the time said envelope exceeds said threshold signal; and, timing means operative at a first speed during the period of each gate signal and operative at a second speed during the period extending from the end of a first gate signal to the beginning of a subsequent gate signal.

Claim 7

Means for detecting the envelope of a radiated beam scanning through space at a receiver illuminated by the beam wherein the receiver includes circuits for producing the envelope of said beam and wherein said beam is radiated from a fixed station and scanned in one cycle from a predetermined position at a constant angular speed to a second predetermined position and return so that said receiver is illuminated twice by said beam during one cycle, comprising: means for generating a signal at a signal level related to a predetermined point on said envelope; analog means for delaying said envelope a predetermined time; means for generating a threshold signal in response to said signal level and displaced a predetermined amount therefrom; means responsive to said threshold signal for generating a gate signal during the time said envelope exceeds said threshold signal; and, timing means operative at a first speed during the period of each gate signal and operative at a second speed during the period extending from the end of a first gate signal to the beginning of a subsequent gate signal.