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Radar System

Pulse-Doppler Radar

PULSE-DOPPLER RADAR SIMULTANEOUS RANGE AND VELOCITY ANTENNA T/RSwitch LNA MIXERCoherent IF AMP A/DSample RANGEGATES Time-domain binning per PRI FFTDoppler Per range bin STALOStable LO COHERENT LO (PHASE REFERENCE) COHOCoherent Osc PULSEModulator PAHigh Pwr TX PULSE TO T/R RANGE FROM TIME DELAY (RANGE GATES) + VELOCITY FROM DOPPLER (FFT PER GATE)
Component Descriptions

Signal Chain Walkthrough

Pulse-Doppler radar measures both target range and velocity simultaneously. It transmits coherent pulse trains and processes returns with range gating (for distance) and Doppler filtering (for velocity). This is the architecture used in modern fighter radars, ATC radars, and weather radars.

Coherent Transmitter (STALO + COHO)

The STALO (Stable Local Oscillator) provides the frequency reference. The COHO (Coherent Oscillator) provides the phase reference. Together they ensure that the transmitted pulses have a known, stable phase relationship, which is essential for Doppler processing.

Range Gates

After digitization, the received signal is divided into time bins (range gates). Each gate corresponds to a specific range. The gate width equals the pulse width, and the number of gates determines the maximum instrumented range.

Doppler FFT per Range Bin

For each range gate, an FFT is computed across multiple pulse returns (one sample per PRI). The FFT output reveals the Doppler spectrum at that range, showing targets and their velocities. Clutter appears at zero Doppler and can be filtered.

Typical Specifications

Component Specifications

ComponentParameterTypical Value
STALOPhase Noise-100 to -120 dBc/Hz @10kHz
PAPeak Power+40 to +60 dBm
PRFPulse Rep. Freq.1 - 300 kHz
Pulse WidthDuration0.1 - 100 μs
Range GatesCount64 - 4096
Doppler FFTSize64 - 1024 point
Velocity ResolutionΔvλ × PRF / (2 × N_pulses)
Design Note: PRF selection involves the range-Doppler ambiguity tradeoff. High PRF gives unambiguous velocity but ambiguous range. Low PRF gives unambiguous range but ambiguous velocity. Medium PRF is a compromise. Modern pulse-Doppler radars use multiple PRFs and resolve ambiguities algorithmically (Chinese Remainder Theorem or similar).
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