ACP-WGS04/WP-05
International Civil Aviation Organization
10/15/2013
WORKING PAPER
AERONAUTICAL COMMUNICATIONS PANEL (ACP)
4th MEETING OF THE WORKING GROUP S
Montreal, QC Canada 15 – 17 October 2013
Agenda Item:
3.1
Environments and Antennas of AeroMACS Signal Evaluation
(Presented by Naoki Kanada,
Prepared by Yasuto Sumiya, Naruto Yonemoto, Makoto Shioji, Akiko Kohmura, Shunichi Futatsumori,
Kazuyuki Morioka)
SUMMARY
This Working Paper elaborates on the experimental results previously
presented by ENRI at the WGS #3 meeting. In addition, the paper reports the
results of antenna pattern measurement. Most antennas have sidelobes in the
vertical plane which are not easy to suppress.
ACTION
The ACP Working Group S is invited to consider relaxing the EIRP limit in
the zenith direction in the area that is not authorized for use by the Fixed
Satellite Service, and to add descriptions of ways to reduce antenna sidelobes
to the AeroMACS guidance material.
(7 pages)
533563475
ACP-WGS 04/WP-05
1.
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INTRODUCTION
1.1
In the WG-S #3 meeting, a number of questions were raised regarding ENRIs working
paper ACP WG-S #3 WP-06:

Whether the results of ENRI’s planned future experiments (RSSI map) should be
included in SARPs or guidance material

Value of antenna gain and details of the antenna used in the experiments

Explanation of figure 6 (Clarification about rain effect and shadows)
ENRI provides information regarding these questions in this paper.
2.
DISCUSSION
2.1
The experiment environment at Sendai airport is explained in the attachment.
Experiments conducted at the west side of the airport frequently switched between Line-Of-Sight (LOS)
and Non-Line-Of-Sight (NLOS) conditions. We confirmed this LOS and NLOS switching by examining
the areas shadowed from an Airport Surveillance Detection Environment (ASDE) antenna co-located with
our AeroMACS base station. NLOS conditions occur when trees interpose between the transmitter and
receiver, and arise at the west side of the airport. The degree of shadowing depends on the season (foliage
density). Trees are not considered in our simulations.
2.2
We measured the radiation pattern of the antenna used in our experiments. The
measurement revealed sidelobes in the vertical plane. Due to these sidelobes, the antenna does not comply
with the current draft AeroMACS SARPs. A similar tendency was shown by another antenna. A large
ground plane on the top of the antenna reduces vertical sidelobes; however, implementation is not easy
because the structure is unstable and the required ground plane size is large. We propose to relax the
EIRP limit in the zenith direction in areas not authorized for use by the Fixed Satellite Service. Easier
suppression of unnecessary radiation is a future research challenge.
3.
ACTION BY THE MEETING
3.1
ACP WG-S is invited to consider relaxing the EIRP limit in the zenith direction in areas
not authorized for use by the Fixed Satellite Service, and to add descriptions relating to antenna
implementation to the AeroMACS guidance material.
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ACP-WGS 04/WP-05
ATTACHMENT: ENVIRONMENT AND ANTENNA PATTERNS
1.
Experimental Environment
This section provides supplemental information to ACP WG-S #3 WP-06.
Figure 1 shows an overview of the ENRI AeroMACS transmitting station. The transmitting
antenna is installed on a tower adjacent to an Airport Surveillance Detection Equipment (ASDE)
installation as shown in the left of the figure. ASDE is a radar for monitoring movements on the airport
surface. Other experimental conditions were described in the previous paper.
Since AeroMACS is a time division duplex (TDD) system, propagation characteristics from a
base station to a mobile station and from the mobile station to the base station are the same due to the
reciprocity theorem.
Figure 1. Experimental Configuration
To determine the Line Of Sight (LOS) / Non Line Of Sight (NLOS) condition between the base
station and antenna more precisely, we examined the shadowing of the ASDE antenna. The main
specifications of the ASDE system are as follows:
 Center Frequency: 24.5 GHz
 Peak Output Power: 30kW
 Antenna Gain: 45dBi
 Range: 3NM (in no-precipitation conditions)
Figure 2 shows the visualized raw ASDE output data. ASDE transmits radio waves, and receives reflected
waves. Figure 2 represents the strength of received reflected waves by color. The strength is colored in
the order red (strongest), yellow, green, and blue (weakest). The radio waves propagate in straight lines to
a high degree due to their high frequency, so transmitted waves do not diffract around the back of
obstacles. Therefore, obstacles are shown as red areas in the figure, and they have blue straight shadows.
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For instance, the Sendai VOR/DME station is indicated in the figure as a red point that has a blue straight
shadow.
Figure 2. ASDE radar output data
Figure 3 shows the environment around the Tx antenna. Figure 3(a) is looking west from the
antenna. A forest and a building with a light blue roof are seen in the westerly direction. A part of a
runway and taxiways cannot be seen due to these obstacles. Therefore, LOS and NLOS environments
frequently alternate in the direction of the airport. Figure 3(b) is looking east from the antenna. The
control tower is seen in the distance, with a terminal building next to it. Some gates and perimeter roads
in front of the terminal are invisible from the antenna because of shadowing.
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(a) View west from the Tx antenna
ACP-WGS 04/WP-05
(b) View east from the Tx antenna
Figure 3. Environment around the transmission antenna
2.
Elevation Antenna Patterns
Two 5GHz Wireless LAN antennas were evaluated for our AeroMACS experiments. It was
necessary to measure the antenna patterns because the antennas were originally designed for Wireless
LAN. Figure 4(a) shows the antenna measurement configuration in an anechoic chamber. The near side of
the figure shows a signal generator and a horn antenna for transmission. At the far side is an antenna
under test. The distance between the two antennas is 10m. This measurement satisfies the far field
condition because the distance is greater than the Fraunhofer distance (9.37 m at 5200 MHz). Figure 4(b)
shows an antenna under test. The white bar is a 21-element collinear array antenna for an IEEE 802.11j
Wireless LAN from 4900 to 5000 MHz. The total length of the antenna elements is 520 mm. White
polystyrene foam supports the antenna and a ground plane. The whole system is placed on a turntable.
The antennas are horizontally omni-directional collinear antennas, so the elevation antenna patterns were
measured at 5000, 5030, 5060, 5090, 5120, 5150, and 5200 MHz.
(a) Antenna measurement system
(b) Antenna under test
Figure 4. Antenna pattern measurement with ground plane on the top
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ACP-WGS 04/WP-05
The results of the antenna pattern measurement in elevation are shown in Figure 5. The antenna
under test in Figure 5 is a Moxa ANT-WSB5-ANF-12, the same model as that used for the transmitting
station in Figure 1. Antenna elements are placed in the upward direction in Figure 5. Units of the axes are
dBi. The measured gain of the antenna is 9dBi at 5120 MHz. The main lobe points 4 degrees downward,
and its half-value width is 10 degrees. The draft EIRP limits are also shown in Figure 5. In the figure, the
output power is supposed as 1W (30dBm) to fit the measurement system. The draft EIRP limits and
antenna patterns in Figure 5 indicate that sidelobes in the upward direction exceed the draft EIRP limits at
all frequencies.
ANT-WSB5-ANF-12 (Elevation)
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5000MHz
5030MHz
5060MHz
5090MHz
5120MHz
5150MHz
5200MHz
Scenario A BS EIRP Limit (Power=1W)
Scenario B BS EIRP Limit (Power=1W)
Figure 5. Antenna Patterns of AeroMACS field experiments
To reduce sidelobes to the zenith, we fixed a ground plane on the top of the antenna as shown in
Figure 4(b) (the silver disc in the figure 4 is an aluminum ground plane of 800 mm diameter). Figure 6(a)
shows the antenna patterns of the Moxa ANT-WSB5-ANF-12 (Antenna 1) with the ground plane (red
line) and without (green line). Similarly, Figure 6(b) shows the antenna patterns of an Antenna
Technology VA510A-11j (Antenna 2) with and without a ground plane on the top. Antennas 1 and 2
show similar characteristics: a ground plane reduces sidelobes by up to 10dB. The figures also show the
EIRP limit of 1W output. The blue lines indicate the EIRP limit for Scenario A, and the purple lines
indicate the EIRP limit for Scenario B in ACP WG-S #3 WP-06. Both of the antennas with ground planes
exceed the EIRP limits at an output power of 1W; however, antenna 2 complies with the Draft EIRP limit
at an output power of 200mW.
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ACP-WGS 04/WP-05
ANT-WSB5-ANF-12 (Elevation) at 5120MHz
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VA510A-11j (modified) Elevation at 5120MHz
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with GP on top
without GP
Scenario A BS EIRP Limit (Power=1W)
Scenario B BS EIRP Limit (Power=1W)
(a) Antenna 1: Moxa ANT-WSB5-ANF-12
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with GP on top
without GP
Scenario A BS EIRP Limit (Power=1W)
Scenario B BS EIRP Limit (Power=1W)
(b) Antenna 2: Antenna Technology VA510A-11j
Figure 6. Antenna patterns with ground planes on the top of the antenna
The results of our measurements are summarized as follows.
First, we have shown that at least some antennas on the market do not comply with the current
draft AeroMACS SARPs. To comply with the draft SARPs, it will be necessary to suppress upwardpointing sidelobes. We show that installing a large ground plane on the top of the antenna is effective at
reducing this unnecessary radiation, but implementation is not easy because of the large physical size of
the ground plane. An easier method of suppressing unnecessary radiation is a future research challenge.
Second, it is necessary to take care with antenna pattern measurement because the Fraunhofer
distance (far field condition) is long for array antennas.
The authors believe that it is necessary to add these observations to the AeroMACS guidance
material(s).