13.0dB 2.6% 1.83% 2.6% 0.62% 2.6% 0.20% 2.8% 0.01%
14.0dB 1.9% 1.45% 1.9% 0.50% 1.9% 0.12% 2.6% 0.01%
16.0dB 1.3% 0.90% 1.3% 0.30% 1.3% 0.05% 5.8% 0.00%
20.0dB 3.1% 0.39% 3.1% 0.12% 2.0% 0.01% 31.5% 0.00%
Note that we can re-tune the constants and operate with C
1
= 13dB and C
2
= 18dB
(fourth column); which yields a low 2.8% Missed rate, and an extremely low 0.01% false
alarm rate. Since the false alarm rate is (approximately) independent of the interference
power, these filter settings would leave "clean" weather virtually untouched. That is, we
would have a safe filter that only removes fairly strong interference. You could leave such a
filter running at all times without too much worry about side eects.
7.2.6
Large-Signal Linearization
When an IF signal saturates, there is still considerable information in the signal since only the
peaks are clipped.
The proprietary large signal linearization algorithm used in RVP900 provides an extra
3 ... 4 dB of dynamic range by accounting for the
eects of saturation. This is possible
because an overdriven IF waveform spends some of its time in the valid range of the
converter, and it is possible to deduce information about the signal.
The following
figure shows signal generator test measurements with normal A/D saturation
(lower line), and with the extrapolation algorithms turned on (upper line). The high-end
linear range begins to roll
o at approximately +10 dBm, instead of +5 dBm, and has been
extended by 5 dB.
Chapter 7 – Processing Algorithms
181
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