Abstract: A radar receiver having a feed-forward control circuit for adjusting the automatic gain control (AGC) setting in 6 dB increments for each range cell in a next sweep based on the AGC setting of each corresponding range cell in the present sweep, the magnitude of the larger of the in-phase (I) or quadrature (Q) components of the video signals of the present sweep from an A/D converter, the status of present sweep and previous sweep A/D limit conditions, and a selected guardband thereby holding the level of the radar return signal within the dynamic range of the A/D converter. The AGC setting is adjusted using a switchable attenuator which changes the level of the video signal into the A/D converter in 6 dB increments, each increment corresponding to a common I and Q data exponent directly used for floating point signal processing.

Abstract: In a radar or sonar system wherein the detection of a target is to be accomplished with a constant false alarm rate (CFAR), a circuit is provided for adjusting the input to a comparator which compares the received echo signals against the value of a threshold in order to detect targets of interest. The mean value of the background noise is subtracted from the signal, and the resulting difference is divided by the square root of the variance of background noise. The use of the variance compensates for sweep-to-sweep correlation and non-stationarity (in the statistical sense) as is found in clutter so that the clutter, upon the customary sweep-to-sweep integration of the signal, does not tend to introduce a false echo.