AD8284 datasheet(12/28 Pages) AD

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AD8284

Data Sheet

Rev. D | Page 12 of 28

THEORY OF OPERATION

RADAR RECEIVE PATH AFE

The primary application for the AD8284 is high speed ramp,

frequency modulated, continuous wave (HSR-FMCW) radar

requiring baseband signal bandwidths of up to 15 MHz. Figure 14

shows a simplified block diagram of an HSR-FMCW radar system.

The signal chain requires multiple channels, each of which is

routed into a low noise amplifier (LNA), a programmable gain

amplifier (PGA), an antialiasing filter (AAF), and an analog-to-

digital converter (ADC). The AD8284 provides all of these key

components in a single 10 mm × 10 mm TQFP package.

The performance of each component is designed to meet the

demands of an HSR-FMCW radar system. Some examples of

these performance metrics include the LNA noise, PGA gain

range, AAF cutoff characteristics, and ADC sample rate and

resolution.

The AD8284 includes a multiplexer (mux) in front of the analog

signal chain as a cost-saving alternative to having an AFE for

each channel. The mux can be switched between active inputs

using the mux pins or through the SPI port.

The AD8284 also includes a saturation detection circuit that

indicates when the LNA or PGA signals are no longer in the

linear region. This feature helps detect fault conditions that

might otherwise be filtered out by the AAF.

Figure 14. Simplified Block Diagram, HSR-FMCW Radar System

DSP

ANTENNA

VCO

AAF

LNA

AD8284

MUX

REF.

OSCILLATOR

CHIRP RAMP

GENERATOR

12-BIT

ADC

SATURATION

DETECTION

PGA

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