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RECEIVER OUTPUT FILTER
CONTROL MOTION NOISE FILTER
PATH FOLLOWING
FILTER = 1; 0 = .64 n
* This corner frequency may be less than 10 rad/sec for some applications.
1 0 2
RECEIVER OUTPUT FILTER (LOW PASS)
PATH FOLLOWING FILTER (LOW PASS)
CONTROL MOTION NOISE FILTER (HIGH PASS)
6dB/OCT
12dB/OCT
6dB/OCT
RADIANS/SEC
ERROR
TIME
OUTPUT OF PFE OR CMN
FILTER
T1 T2 T4
T3
T = SLIDING
WINDOW
(= T seconds)
IA
MODE
FA
MODE
T 40 sec 10 sec
DME/P measurement methodology: is the error specification; T region to be evaluated; T , T , T ... time intervals that error
exceeds specifications. For the equipment to be acceptable in this region, the following inequality should be true:
(T + T + T + ...) / T 0.05.
1 2 3
1 2 3
2
S + 2
n
n n
2
S2 + 2 S + 2
S
S + 1
Figure C-21
ATT C-79 23/11/06
Annex 10 — Aeronautical Communications Volume I
7.3.5.5 Outlier rejection
Range estimates which are significantly different from previous filtered range estimates, because they cannot be the
result of aircraft motion, should be assumed to be in error. Such data should be rejected at the input to the data filter.
7.3.6 DME/P error measurement methods
7.3.6.1 System errors
7.3.6.1.1 The DME/P system accuracies are specified in Chapter 3, 3.5.4.1.3.4 in terms of path following error (PFE)
and control motion noise (CMN). These parameters describe the interaction of the DME/P guidance signal with the aircraft in
terms directly related to aircraft position errors and flight control system design.
7.3.6.1.2 For the purposes of determining compliance with the accuracy standard, the PFE and CMN components are
evaluated over any T second interval (where T = 40 seconds in the IA mode and 10 seconds in the FA mode) of the flight
error record taken within the DME/P coverage limits. The 95 per cent probability requirement is interpreted to be satisfied if
the PFE and CMN components do not exceed the specified error limits for a total period that is more than 5 per cent of the
evaluation time interval. This is illustrated in Figure C-21. To evaluate the PFE and CMN components of the DME/P
guidance data, the true aircraft position, as determined by a suitable position reference, is subtracted from the guidance data
to form an error signal. This error signal is then filtered by the PFE and CMN filters, where the outputs provide suitable
estimates of the PFE and CMN components, respectively. These filters are defined in Figure C-21.
7.3.6.1.3 These filters can be utilized to determine the transponder instrumentation error components specified in
Chapter 3, 3.5.4.5.3 and 3.5.4.5.4. Similarly, the interrogator instrumentation error components, specified in Chapter 3,
3.5.5.4, can be determined.
7.3.7 Multipath effects
7.3.7.1 Under the multipath conditions likely to exist, the accuracy specifications of the DME/P assume that the
performance is not degraded beyond a certain limit and that this degradation is equally applied to both interrogator and
transponder receiver.
7.3.7.2 To ensure that the equipment is working according to the specifications, the following should apply to FA
mode operation of the system:
a) if a signal of sufficient power to make thermal noise contributions insignificant is applied to the receivers, a second
signal delayed between 0 and 350 nanoseconds with respect to the first, with an amplitude 3 dB or more below the
first and with a scalloping frequency between 0.05 and 200 Hz should not produce errors in the receiver output of
more than plus or minus 100 nanoseconds (15 m);
b) for delays more than 350 nanoseconds the error contribution will be reduced considerably. A typical value will be
plus or minus 7 nanoseconds (1 m).
7.3.7.3 The airborne DME antenna should be located so as to preclude antenna gain reductions in the forward direction
with the aircraft in the landing configuration. Any such antenna gain reductions could enhance the multipath error component
when the aircraft is on approach and landing phases when highest DME accuracies are required.
7.3.8 DME/P power budget
7.3.8.1 Tables C-7 and C-8 are an example of CTOL air-to-ground and ground-to-air power budgets. The permitted
peak ERP value is based on a pulse shape which meets the spectral constraints in Chapter 3, 3.5.4.1.3 e).
23/11/06 ATT C-80
Attachment C Annex 10 — Aeronautical Communications
Table C-7. CTOL ground-to-air power budget
Power budget items
41 km
(22 NM)
13 km
(7 NM)
Ref.
datum Roll-out
Peak effective radiated power, dBm 55 55 55 55
Ground multipath loss, dB –5 –3 –4 –17
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