Instrumentation & Measurement Magazine 25-8 - 27

arc on ILS: most of the existing research assumes that the antenna
of the communication navigation station is an ideal
non-directional antenna. Signals radiate into space as spherical
waves, which will inevitably lead to large errors in the
analysis results.
In this article we put forward a new method to study the effect
of pantograph-catenary arc on ILS at airports.
Electromagnetic Environment
Requirements of ILS
Presently, the ILS is the main landing guidance equipment,
commonly known as the blind landing system, which is aimed
to guide the aircraft's precision approach landing at the airport
terminal area. The ILS consists of the Localizer (LOC), Glide
Slope (GS) and Marker Beacon (MB) [19]. We take the GS, the
working frequency of which is 328.6 MHz to 335.4 MHz, as an
example to study the influence of pantograph-catenary arc in
this article.
When the aircraft is approaching landing, in order to ensure
the normal operation of the ILS, the Protection rate or R of
each beacon of the ILS should be satisfied as [20]:
E 
sn
where Es
received by the aircraft and En
E R
(1)
is the electric field intensity of the navigation signal
is the electric field intensity of
the active co-frequency disturbance signal received by the aircraft.
Table 1 gives the requirements of protection rate of the
ILS [21].
Test Setting and Test Results
Test Setting
In order to acquire the radiation characteristics of pantograph
arc in its entirety, we chose three sites, phase separation (PS),
overlap (OL) and normal site (NS) at Chengdu Shuangliu International
Airport in Chengdu, China. The test site figures are
shown in Fig. 1, while the test system framework is shown in
Fig. 2. Since the data is tested by the point-frequency model of
electromagnetic interference receiver, the difference of the arc
discharging energy on each frequency point does not exceed
1 dB in the GS frequency band. Therefore, one of the typical
frequency points is selected for testing, and 330.5 MHz is what
this article implemented. The tested electric field intensity can
be obtained by the following formula:
EU AF L
 
(2)
where U is the voltage at the receiver port; AF is the antenna
coefficient; and L is the cable loss. The test distances are shown
in Table 2.
The test antenna model is the log-periodic antenna, model
R&S HL223, whose performance parameter is shown in Fig. 3.
Since the values specified in GB/T 6364-2013 are tested by
the 10 m-method, the actual test environment is unable to meet
the standard of the 10 m-method. Consequently, we have to
November 2022
Fig. 2. Test system framework.
Test site
Distance (m)
IEEE Instrumentation & Measurement Magazine
Table 2 - The test distances
PS
79
OL
26
Fig. 1. Test site.
Table 1 - The protection rate requirements of ILS
Beacon
Frequency
(MHz)
LOC
GS
MB
108.1 ~ 11.95
328.6 ~ 335.4
75
Protection rate
(dB)
20
20
23
NS
41
27
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