Vaisala RVP900, Руководство пользователя

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Information Line Description
PSL
Peak sidelobe level of the ambiguity diagram, expressed in deciBels relative to the
main lobe level. This is the peak height of the strongest range/time sidelobe, and
measures the ability of the compressed pulse to distinguish a given target from a
small number of individual point targets that also lie within the pulse volume. The
waveforms ability to "see" between clutter targets is largely determined by the PSL
level.
ISL
Integrated sidelobe level of the ambiguity diagram, expressed in dB relative to the
main lobe. This is the total power in all range/time sidelobes divided by the total
power in the main lobe. ISL measures the ability of the compressed pulse to
distinguish a given target from other distributed targets (such as rain) that also lie
within the pulse volume.
TxLoss
The TxLoss is calculated as the total power in the transmit waveform divided by the
power that would be contained in an equal length ideal rectangular pulse. It is a
measure of how much power does not get transmitted due to the amplitude shaping
of the synthesized waveform.
TxLoss should be included in the computation of the radar constant, since the latter
is based on a nominal pulsewidth equal to the overall length of the entire Tx waveform
(including the amplitude tapering).
RxLoss
The RxLoss is a measure of how much information is discarded by the receiving filter
in order to achieve the desired level of sidelobe suppression. These two quantities
often trade off against each other in receiver systems, so that optimum range/time
sidelobes can only be achieved at the expense of a few deciBels of loss of sensitivity.
The receiver filter loss is calculated as:
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= − 10log
10
∫� � ����
2
∫ � �
2
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2 2
Where T(t) is the complex-valued transmit waveform, and R(t) is the complex-
valued filter being used to receive it.
When
R(t) is designed to be the complex conjugate of T(t) , we have the ideal
matched filter case whose receive loss is 0 dB. However, this matched filter has rather
poor sidelobe behavior that makes it unsuitable for use directly in the receiver.
Instead, a windowed version (Hamming, Blackman, and so on) of the ideal matched
filter is used to achieve the desired sidelobe levels. The windowing operation also has
the effect of discarding some valid information in the leading and trailing portions of
the pulse. Hence, there is a loss in receive sensitivity when a window is applied.
Given a compressed transmit waveform, RVP900 designs the appropriate mismatch Rx
filter automatically, using an optimized Blackman window in all cases. Developers can also
access the internal APIs directly to design any desired transmit waveform along with the
associated FIR filter to receive it.
6.8.4 Bench Testing Compressed Waveforms
Once the Tx waveform has been designed, you can inject it into the IFDR for testing with the
Pr command.
Chapter 6 – Plot-assisted Setups
165