Self-calibrating threshold detector
First Claim
1. In a system for receiving an incoming signal modulated by a prescribed code, the combination comprising:
- a. a correlator receiving said incoming code and successively cross-correlating same with a local replica of said incoming code and with an incorrect code, said correlator producing during one time interval a reference signal corresponding to the correlation with said incorrect code, and further producing during a successive time interval an output signal corresponding to the correlation with said replica code;
b. hold means holding a sample of said reference signal; and
c. comparator means comparing said sample reference signal with said output signal to provide a resultant difference signal indicative of said correlation with said replica code.
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Abstract
A self-calibrating threshold detector for use with receivers adapted to receive an incoming transmitted signal carrying a prescribed code. The detector comprises a single demodulating channel which includes a mixer having one input receiving the incoming signal and another input receiving a local replica code. During a short time interval, an incorrect local code is applied to the mixer to incorrectly demodulate said incoming signal and to provide a reference level that calibrates the noise propagating through the channel. A sample-and-hold circuit is coupled to the channel for storing a sample of the reference level. During a relatively long time interval, the correct replica code provides an output level which ranges between the reference level and a maximum level that represents incoming signal presence and synchronism with the replica code. A summer subtracts the stored sample reference from said output level to provide a resultant difference signal indicative of the acquisition of the expected signal.
14 Citations
6 Claims
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1. In a system for receiving an incoming signal modulated by a prescribed code, the combination comprising:
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a. a correlator receiving said incoming code and successively cross-correlating same with a local replica of said incoming code and with an incorrect code, said correlator producing during one time interval a reference signal corresponding to the correlation with said incorrect code, and further producing during a successive time interval an output signal corresponding to the correlation with said replica code; b. hold means holding a sample of said reference signal; and c. comparator means comparing said sample reference signal with said output signal to provide a resultant difference signal indicative of said correlation with said replica code. - View Dependent Claims (2, 3, 4, 5, 6)
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Specification