Overview

The analogue-to-digital converter changes analogue (usually bipolar) video signals into (parallel) digital values, which can be processed by hardware similar to that in computers. Radar hardware normally provides vector processing, so two converters are necessary. Two types of conversion are possible:

• The two Cartesian components from the synchronously detected intermediate frequency signal, I and Q videos;

• Amplitude and phase from a linear detector and phase detector, respectively.

Generally signal processors use data streams formed from the Cartesian components. The matched filter determines the bandwidth of the videos from the detectors. The range clock tells the analogue-to-digital converter to take samples at fixed intervals during the listening or processing time.

10.1 Principle

The converter changes the input voltage into a stream of measurements of the voltage expressed as binary integers. Each binary digit represents a doubling of the voltage, that is, a 6 dB power change. Analogue-to-digital converters are available as commercial integrated circuits.

The videos from the synchronous detectors are bipolar videos so that the voltage range is from a negative maximum to a positive maximum. One binary bit is used for the sign. Common analogue-to-digital converters used in radar convert 8, 12, or 16 bits. When one bit is used for the sign, the dynamic ranges are shown in Table 10.1.

Amplitude and phase videos...