Doppler Weather Radar - METNET - India Meteorological Department

MDDS and Noise Figure Test
Figure C.3. An Example Dynamic Range Test Results
To verify the MDDS (Minimum Digital DetecTable Signal) over the Complete Receiver
Chain, the receiver noise level power will be tested first. After that, an external signal will be
injected to the LNA. The receiver output noise level (actually, in this case, test signal plus noise)
will be measured using Zauto while the input signal level is increased. When the receiver output
signal plus noise level is 3 dB higher than the noise only level, the input signal power from the
external signal generator is equal to the MDDS.
Configuration
Connect an external signal generator to the input of the LNA. Set the frequency of the
generator to the site operating frequency. Use a cable with a calibrated loss at the site operating
frequency and account for this cable loss in calculating the input power to the LNA. The signal
will go through the normal Receiver Channel including the RVP8 Digital IF and RVP8 down
conversion process. The Zauto utility will be used to measure the power in the I and Q received
digital samples (see Figure C.4).
Ratio of Reverse and Forward Power (dB)
External signal Generator
Low Noise
Amplifier
Receiver Output on
Zauto
Receiver Channel
Figure C.4. MDDS Test Configuration
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