Metek's Micro Rain Radar (MRR2) is a vertically pointing FMCW (Frequency Modulated Continuous Wave) radar. This means that, in contrast to the other radars operated within KITcube, it does not transmit pulsed but continuous signals. To allow the assignment of distance (height) information to the measurements the transmission frequency is changed periodically in accordance with a "sawtooth pattern".

At each measurement height, the MRR2 determines a spectrum, i.e. it determines how much energy was scattered back at a given Doppler shift. Assigning different drop sizes to specific fall velocities allows then the derivation of the droplet size distribution at each measured height – assuming that all droplets consist of liquid water.

Fig. 1: |

Specifications of K-band FCMW Doppler radar

Frequency: 24,230 GHz

Wavelength: 1.24 cm

Operating mode: FM-CW (sawtooth with downsweep)

Repetition time of sawtooth: 0.514 ms

Sawtooth frequency shift: 1953 Hz

Continuously radiated power: 50 mW

Diameter of the parabolic mirror: 60 cm

Beam width (-3dB one-way limit): 1.5 deg.

Near field distance ~ 20 m

Side lobes: <-20 dB

Sample rate of the A/D-converter: 31.25 kHz

Discrete data points per FFT: 1024

Frequency strokes per FFT (N): 64

Period of an FFT: 33 ms

Nyquist frequency: 15,625 kHz

Discrete frequencies of the power spectrum: 512

Frequency resolution: 30.25 Hz

Speed resolution: 0.19 ms^{-1}

Number of height levels: 32 (of which 30 are usable)

Speed channels per altitude level: 64

Height resolution: 10-200 m (adjustable)

Number of single spectra in a 10 second average: 138

Averaging time for output: 10-3600 s (adjustable)

Manufacturer: Metek GmbH, Elmshorn