초록 ▼

In a spread-spectrum receiver, a predetermined noise floor voltage, supplied together with the output of the correlation detector as a control voltage for an AGC amplifier, is subjected to a pre-signal reception adjustment or calibration, in order to compensate for drift in the noise floor or refere

In a spread-spectrum receiver, a predetermined noise floor voltage, supplied together with the output of the correlation detector as a control voltage for an AGC amplifier, is subjected to a pre-signal reception adjustment or calibration, in order to compensate for drift in the noise floor or reference voltage and to correct for gain errors in the correlation detector channel thereby insuring proper operation of the detector during the sequential detection process. For this purpose, a prescribed random signal sequence, totally different from that contained in any useful transmission to be acquired, is initially applied to the correlation detector for a predetermined period of time or calibration interval. The output of the correlation detector is sampled and stored, successive samples are compared with the predetermined or fixed reference noise floor voltage, and successive adjusted noise floor reference values are produced, representative of differences between the noise level in successive correlation samples and the predetermined noise reference. These adjusted reference values are accumulated and this accumulated noise floor is fed back to the AGC amplifier as the noise floor control reference. At the end of the calibration interval, the receiver is switched to a normal operating mode and control of the AGC amplifier is determined by the noise floor reference level which has been adjusted or calibrated to the voltage represented by the accumulated noise floor level at the end of the calibration interval. Preferably, the calibration circuitry is implemented in digital form, with the duration of the calibration interval being controlled by a digital counter which counts clock pulses up to a prescribed number and then prevents further accumulations of noise reference values. The output of the counter may also be coupled as a control signal to cause a spread-spectrum signal acquisition PN sequence to be substituted for the random noise sequence which had been applied to the correlation detector during the calibration mode.

대표청구항 ▼

In a receiver system having an automatic gain control feedback loop for controlling the gain of a received signal amplifier, a system for calibrating the operation of said gain control feedback loop comprising: first means for monitoring the output of said received signal amplifier during receiver o

In a receiver system having an automatic gain control feedback loop for controlling the gain of a received signal amplifier, a system for calibrating the operation of said gain control feedback loop comprising: first means for monitoring the output of said received signal amplifier during receiver operation in the presence of a prescribed noise input; and second means, coupled to said first means and to said received signal amplifier, for comparing the monitored output of said received signal amplifier with a prescribed reference that is independent of the contents of the output of said received signal amplifer and adjusting the operation of said feedback loop in accordance with the deviation of said monitored output relative to said reference, and wherein said second means includes means for accumulating the deviation of said monitored output relative to said reference for a prescribed interval of time and adjusting the operation of said feedback loop in accordance with the accumulated deviation.