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Airport air traffic radio interference investigation and case analysis

In Electronic Infomation Category: A | on May 03,2011

2010, the Civil Aviation Air Traffic Control Branch of Shandong Radio Management Office of Shandong Province, to reflect, Jinan Airport VHF air-ground communications station in the near future with a frequency of 122.900MHz persistent noise, transceiver RSSI value is shown by the normal circumstances of-108dBm to-101dBm about the following increases, thereby affecting the receiver to the ground plane on the route the remote receiving communication signals, so that the safety of navigation has greatly increased the potential hazards.

This, Radio Management Office of Shandong Province, is very concerned for immediate investigation and TLP521-1GR datasheet and monitoring stations organizing forces. After several tests, find several related signals, but after analysis of authentication, are non-interference was ruled out one by one. As the interference signal is very weak, common test equipment to the interference signal is difficult to capture, and TLP521-1GR price and location finding more difficult. Test system integration and TLP521-1GR suppliers and wireless communications solutions provider of Beijing Technology and TDF through the end of December last year, sent engineers to carry Tektronix H600 portable wireless signal detection device for assistance. Tektronix Tektronix H600 is produced by the United States with real-time spectrum analysis, the transient and the burst capture weak signals with strong instrumentation, the advantages of these techniques interfere with the searching process has been fully validated.

Radio stations and in Shandong Province, China Ying technology through technical staff under the pre-test analysis of the situation that the more serious interference signal near the tower. Therefore, first floor office tower test, found in the water supply system has several RFID equipment used to control the water supply system, so in the vicinity of the RFID testing and found that there are multiple interfering signals, the signal shown in Figure 1 Screenshot said:

Figure 1: there are two emission signals

But close to the RFID device, the control tower response interference signal still exists, and no improvement. Prove that the RFID device although the signal tower near the working frequency band, but not really interfere with the signal.

Subsequently, the test of science and technology through TDF personnel directly to the tower to test the engine room. Testing room tower at the airport to test that, 122.900MHz there are several nearby signals, see Figure 2:

map 2:122.906 MHz and 122.893MHz two signals into a 122.900MHz

Communication channel. Comparing Figure 3 (shown in blue channel large signal that is 122.900MHz instant call spectrum), indicating that these two signals and some of the signal is 122.900MHz channel interference signal.

map 3:122.900 MHz channel called transient spectrum

To eliminate external interference factors, testers and outdoors around the tower to the road test, running 100 meters for every meter automatically records the time the test results (Figure 4).

Figure 4: In the outdoor test spectrum

Road test results not received in the flat basic signal interference, guessing may be due to low-lying cause, testers went to the middle part of the test tower, still can not find that interfering signals, which concluded that the interference signal may not come from outdoor equipment, but some equipment from the interior due to stray radiation.

Figure 5: After the cabinet near the interference signal strength indication Then the tester back

tower room, the indoor facilities were tested. When the spectrum analyzer when the equipment cabinet near one of the interfering signal increased significantly (Figure 5), concluded that the cabinet had an interfering signal equipment. After the equipment cabinets one by one on the power experiments, and found a group of photoelectric conversion device is made of the interference signal emitter.

Figure 6 is a signal device is turned off before and after the cursor change:

closed before closing

Figure 6: Turn off the signal jamming equipment before and after the change

Close the photoelectric conversion device, transceiver back to the-110dBm RSSI indicators below, the sound demodulation noise disappeared almost normal air-ground communications, the source of interference is further proof. The radio frequency interference

investigation gave us some tips, a wide range of civil disturbance, also a variety of reasons, such as from a variety of different uses within the engine room equipment. Some seemingly unrelated devices may also generate RF signal leakage, resulting in interference with communications equipment. This case identified the photoelectric conversion device, but the quality of the related components, equipment aging, and poor system stability reasons, making the device work long hours when the spurious signal leakage and radiation of VHF air-ground communication station in caused by continuous noise frequency 122.900MHz. The case also shows that, similar to radio frequency interference in the investigation, the first rule out the system itself and the engine room of the reasons for other equipment, procedures and practices is essential.

Figure 7: The frame problem and the faulty equipment

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