MIL-DTL-52872D
3.5.2.2.1. Alarm criteria for noise. The UMS shall be in the alarm state
after broadband ultrasonic noise, as described in 3.5.2.2.1.1, that exceeds
the RSPL at the receive transducer by 65 dB has been applied to one
transceiver in a motion-free area for 5 seconds or more with its range control
set to maximum and all other transceivers placed in an acoustically quiet,
motion-free area.
3.5.2.2.1.1. Spectrum of broadband ultrasonic noise. The broadband
ultra-sonic noise shall be that produced by a band-limited white noise
generator producing a uniform noise output in the 25.3-27.3 kHz band when
applied to a suitable transducer (see Appendix A, figure 1). The 3 dB
bandwidth shall be 5 to 30 kHz with a 6 dB/octave slope outside this
bandwidth.
3.5.2.2.2. Alarm criteria for unidirectional motion. For a constant
setting of the transceiver range control, the UMS shall be in the alarm state
in accordance with table I upon receipt of the ultrasonic Doppler signals
simulating the unidirectional motions listed in table I with velocities in the
range 0.55 to 17.6 fps. The UMS shall detect such motions in the presence of
the ultrasonic clutter signal in accordance with table I. The UMS shall be in
the non-alarm state when only the clutter signal is present and when neither
the clutter signal nor the unidirectional Doppler signal is present. Unless
otherwise specified herein, the performance described in this paragraph shall
be obtained with only a single transceiver operating with a processor.
TABLE I.
Schedule of UMS states for sums of simulated Doppler signals and
clutter signals.
Simulated ultrasonic Doppler. Signal 1/
Type of motion
Target
Target
Ultrasonic
UMS state
radial
duration or
clutter
velocity fps
period 3/
signal 4/
2/
Unidirectional
0.55
960 ms
None
Alarm
Unidirectional
1.1
780 ms
Present
Alarm
Unidirectional
2.2
570 ms
Present
Alarm
Unidirectional
4.4
380 ms
Present
Alarm
Unidirectional
8.8
310 ms
Present
Alarm
Unidirectional
17.6
300 ms
Present
Alarm
None
-
-
None
Non-alarm
None
-
-
None
Non-alarm
Oscillating
0.55
2 sec
None
Non-alarm
Oscillating
1.1
2 sec
Present
Non-alarm
Unidirectional
1.138
1 sec
None
Non-alarm
Unidirectional
35.2
1 sec
None
Non-alarm
Notes:
1/
The simulated ultrasonic Doppler signal shall be obtained from a
Doppler signal synthesizer (see 6.4.4) and shall simulate the listed
target motion. The simulated Doppler signal shall exceed the RSPL at
the receive transducer by no more than 40 dB, unless otherwise noted.
2/
For approaching and receding radial velocities of 17.6 fps, the
simulated ultrasonic Doppler and clutter signals shall be applied to
one transceiver, with 19 other transceivers located in an acoustically
quiet area connected to the processor by up to 500 feet of RG-58/U
cable. The sound pressure level of the simulated ultrasonic Doppler
signal at the receive transducer shall not exceed 55 dB above the RSPL.
The 19 transceivers and cable may be simulated by suitable electronic
circuits having impedances and noise characteristics equivalent to
those experienced in a typical string of 19 transceivers.
6
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