Analog clutter cancellation algorithms for dynamic range reduction

Abstract

Advanced radar receivers having an instantaneous dynamic range exceeding 90 dB are currently under development. These receivers must operate linearly to achieve satisfactory performance in a severe clutter environment. Presently available, state-of-the-art analog-to-digital converters ( ADCs) having sufficiently high sampling rates do not have adequate dynamic ranges to digitize the outputs of these receivers.A technique has been developed that effectively reduces the dynamic range of the input signal prior to digitization. The dynamic range reduction is accomplished through a process that predicts the next radar return signal from the previous return signals, generates a replica waveform, and subtracts this replica waveform from the radar return signal prior to digitization. This process allows the radar return signal to be digitized without distortion by an ADC having a limited dynamic range. The full dynamic range of the radar return signal is then restored by adding the replica waveform to the ADC Output. Tests and evaluations using both synthetic and recorded radar data have demonstrated in excess of a 30 dB reduction in the dynamic range of the signal at the ADC input when strong clutter is present.

A stacked A-to-D converter for increased radar signal processor dynamic range

“…The technique of digital feedback to an analog attenuator uses a control signal, originating in the signal processor, to control an analog attenuator in the receiver in order to continuously ensure that signal, noise, and clutter levels fall inside the dynamic range of the ADC [2]. However, with this type of approach, it is difficult to maintain low switching transients and sufficient accuracy to support a high value of clutter suppression.…”