Defining IFDR10 input A/D saturation levels

IF input and burst input

The A/D input saturation level for the IF input and burst input is +12 dBm.

In most installations, an external, anti-alias filter is installed on both of these inputs. These filters (when supplied by Vaisala) are mounted externally on one side of the IFDR, and have an insertion loss of 0.5 dB ... 1.0 dB. The input saturation level is +12.5 dBm ... +13.0 dBm, measured at the filter inputs.

For the burst pulse, it is important not to exceed the A/D saturation level. This reference signal should be strong enough, so that most of the bits in the A/D converter are used effectively, but it should also allow a few decibels below the saturation level for safety. The recommended power level is in the range -10 dBm ... +4 dBm. This is important for making a precise phase measurement on each pulse.

See Burst pulse timing plot (Pb).

IF receiver input

For the IF receiver input, it is useful to occasionally exceed the A/D input saturation level at the strongest targets. However, inputs must not exceed 20 dBm. RVP10 uses a statistical linearization algorithm to derive correct power levels from targets that are as much as 6 dB above saturation.

Establish the IF signal level by weak-signal and noise considerations, rather than by working backwards from the saturation level.