Instrumentation & Measurement Magazine 25-8 - 29

Test site
Table 3 - 330.5 MHz test results
Background
PS
OL
NS
U (dBμV)
13
13
13
E10
(dBμV/m)
27.7
27.7
27.7
generated by pantograph arc is taken into primary consideration
when we analyze the influence of pantograph arc
radiation field intensity on airport GS. If the difference between
the contributing signal received by the aircraft and the
interference signal generated by the pantograph arc is greater
than the protection rate at the same frequency, then the interference
can be ignored; otherwise, the interference will definitely
affect the aircraft. The relative position of the railway and the
airport runway is illustrated in Fig. 6. where the sliding angle
θ of the aircraft is 3°, the farthest coverage distance of the GS is
18.5 km and the minimum signal field intensity is 400 μV/m.
From Fig. 6, we obtain:
h  x tan 
ds h22  150 
x  300
dn  22
h s
sition x:
Es  20lg400 20 lg

 

18500
ds
dBµV m
/
(7)
From the test data in PS, we obtain the radiation field intensity
generated by pantograph arc at position x:

En
  

75.65 20lg
10
dn
RE E
  
sn 20lg400 20lg
dBμVm
/
Following from (1), the protection rate is:

18500 
300
  
x
  
75.65 20lg (10)
dn


10
(8)
2
(4)
(5)
(6)
From (3), we get the minimum signal field intensity at poComparative
Discussion
Authors of [5], proposed a method to analyze the EMI influence
of the pantograph-catenary arc, and the computational
processes are as follows:
◗ The transmitting power of the transmitting antenna is
known as Pr;
◗ Assume that the antenna of the ILS is an omnidirectional
antenna ILS signals radiate into space in the form
of spherical waves.
◗ Then, calculate the field strength value at a certain
distance according to the principle of radio wave
propagation.
However, the actual ILS antenna has strong directivity,
which inevitably leads to the fact that the actual signal strength
in the direction of the aircraft landing is much larger than that
calculated in the literature [5], [6], and the calculation results
are not accurate enough.
Therefore, we present
the comparison results of
the two methods, as shown
in Fig. 9.
From Fig. 9, we can see
Fig. 6. The relative position of airport runway and the railway.
November 2022
IEEE Instrumentation & Measurement Magazine
that the protection distance
calculated by the existing
method is 10000 m, which
is much longer than that
calculated by the method
in our research presented
here. According to previous
analysis, it is apparent
that we can safely come to
29
U (dBμV)
43
33
32
Pantograph arc radiation
E10
(dBμV/m)
75.65
56.00
58.95
Firstly, we get the curve of R with distance x at different
sites when the distance between runway and railway is
steady-state, as shown in Fig. 7.
From Fig. 7, we witness a gradual decline in the protection
rate with the increase of the distance between the aircraft and
the entrance to the runway. As a result, we consider that the
distance between aircraft and the entrance to the runway is
steady-state, and we get the curve of R with distance s at different
sites, as shown in Fig. 8.
From Fig. 8, we obtain the minimum distance between the
phase separation and the entrance to the runway, which is
called the protection distance. In this case, the protection distance
is 6794 m. Consequently, the protection recommendation
we propose is that the distance between PS and ILS should be
greater than 6794 m.

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