Quote:
Originally Posted by SeaQueen
I actually wrote a short program to generate Gaussian distribute random numbers. I use it for various projects of mine. I could send you the source if you'd like.
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Sure, I'd be interested in seeing that!
Quote:
Originally Posted by SeaQueen
Like... on the top display I assume I'm looking at frequency versus the received level (in dB?).
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We never actually measured incoming signals in dB, dBm, or any specific units (unless the ESM system was being groomed). We used the crude, but effective, signal strength scale I outlined in the readme:
-SS-1, signal is barely discernible from background noise. No side lobes detectable.
-SS-2, signal is clearly discernible from background noise, but still relatively weak.
No side lobes detectable.
-SS-3, signal is clearly discernible and of moderate strength. There may be some weak
side lobes present.
-SS-4, signal is strong, with several side lobes clearly discernible/audible.
Depending on other parameters, this represents a possible detection or collision threat.
-SS-5, signal is very strong – the receiver is saturated, i.e. little or no distinction
can be made between the side lobes and the main lobe. Depending on other parameters, this
represents a detection or collision threat.
This worked great if you kept in mind the characteristics of the radar signals and how they affect the capabilities of the radar (range, resolution, etc).
Quote:
Originally Posted by SeaQueen
The other two displays I'm not sure I understand entirely.
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The other two displays are the demodulated radar pulses. The first pulse analysis display (the middle display) shows multiple pulses so that the Pulse Repetition Interval can be measured. The second display shows a single pulse so that the pulse width can be measured.
Here's the ESM Quick-tutorial part of the readme:
ESM Quick-tutorial – ESM stands for Electronic Surveillance Measures, and is basically the passive
(receiving or listening) side of ECM, or Electronic Countermeasures (or EW, Electronic Warfare).
ESM performs several functions in a military context:
-identification of platforms in a tactical situation, to identify both friendly and enemy forces
-evaluation of signal strength and emitter type, to determine whether or not the emitter’s platform
is a detection threat (i.e. will be able to detect ownship using the emitter detected by ownship)
or a collision threat (i.e. the signal strength is so high that ownship is within the radiation
pattern of the emitter, close enough to be a hazard to ownship)
-reconnaissance of sea-based, airborne or landbased platforms for the purpose of gathering intelligence,
either in a tactical or non-tactical situation
All intelligence gathered using ESM is Signals Intelligence, or SIGINT. SIGINT includes intelligence
about various RF signals, which includes radar and communications signals. This simulator only depicts
intercepted radar signals.
Signal Parameters – the basic parameters of concern that are typically measured by an ESM system are:
-frequency in MHz (or GHz, 1GHz = 1000MHz). In general, the lower the frequency, the longer
the detection range. Typical marine navigation radars operate in the 8000-10000MHz range, while a
long-range early warning air search radar might operate at about 300MHz.
-Pulse repetition interval in microseconds (us); the duration between the leading edge of one pulse
to the leading edge of the next. In general, the longer the PRI, the longer the detection range.
-Pulse repetition frequency in pulses per second (pps), which is the reciprocal of the PRI; the number
of pulses transmitted by the emitter per second. In general, the lower the PRF, the longer the
detection range, which corresponds to a longer PRI.
-Pulse width in microseconds (us); in general, the longer the pulse width, the longer the detection range,
because of higher average power output. However, a longer pulse width contributes to a lower
range/target size resolution. A radar with a short pulse width is better able to distinguish between
multiple targets that are close together.
-Scan rate in seconds; this usually only applies to circular or sector scans. Scan rate is not measured
by this simulator.
-Signal strength – depends on who’s doing the measuring. Back when I was on the boat, we had a 5-level
signal strength system:
-SS-1, signal is barely discernible from background noise. No side lobes detectable.
-SS-2, signal is clearly discernible from background noise, but still relatively weak.
No side lobes detectable.
-SS-3, signal is clearly discernible and of moderate strength. There may be some weak
side lobes present.
-SS-4, signal is strong, with several side lobes clearly discernible/audible.
Depending on other parameters, this represents a possible detection or collision threat.
-SS-5, signal is very strong – the receiver is saturated, i.e. little or no distinction
can be made between the side lobes and the main lobe. Depending on other parameters, this
represents a detection or collision threat.