ZCU216 · FMCW · GHz · vertically pointing

Ka-Band Rain Column

The TX array (4 channels) steers its beam by phase, or in MIMO mode fires one TX at a time. Wavefronts leave the radar and echo back from each layer only when its reflectivity clears the minimum detectable Z. Heights to scale; radar enlarged about 2000×.

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Receiver

Beam

Mechanical elevation

Electronic steering (TX phase)

Element spacing λ/2: channel n gets φ_n = −180°·n·sin θ. Four elements set a beam about 26° wide; the 20° beam in the link budget comes from the full sub-array.

wavefronts echoes range gates animate

MIMO · 4 TX × 4 RX (TDM)

MIMO mode angle bins wind arrows

v_r − mean across the beam

In MIMO mode the TX channels fire in turn (colors) and the angle is formed digitally from the 16 virtual elements. The fan shows each angle bin, colored by how much faster (red) or slower (blue) the rain approaches than the beam average. The left/right tilt of that pattern is the horizontal wind, shown as arrows: solid = retrieved, grey = truth.

Layers along the beam

Reflectivity profile (simulated, vertical beam)

Doppler spectrogram (simulated)

Rain falls at 6–7 m/s with a wide spectrum; its fast tail wraps past +v_max to −v_max. The bright band is where fall speed jumps from snow (~1.5 m/s) to rain.