## 5 Quantitative Evaluation of the Influence of Some Typical Parameters on the Balise Uplink Signal
Figure 17: Variation of uplink received signal power with different installation modes (active balise). Figure 18: Variation of uplink received signal power at different vertical distances between the OAU and the balise. Figure 19: Variation of uplink received signal power at different lateral deviation between the OAU and the balise. Figure 20: Variation of uplink received signal power with different uplink transmitting current intensity (active balise). The influence of the lateral or longitudinal installation of the rectangular OAU and balise on the uplink received signal power is shown in Figure 17. Since the signal power at the onboard receiving antenna terminal is symmetrical along the OX axis, we only needed to plot the curve of the positive half of the OX axis. The lateral or longitudinal installation of the rectangular OAU and balise had little effect on the main lobe and side lobe peak power of the received signal. However, the null distance was obviously related to the installation of these antennas. When the OAU and balise were installed longitudinal, the null distance was 88 mm longer than the null distance when these antennas were installed lateral. Therefore, when both the OAU and the balise were installed longitudinally, the width of the main lobe of the displacement-power curve was the widest. This meant that under the same dynamic contact distance, the attenuation of the received signal power with the longitudinal displacement of the antenna was the least in this installation mode. The intensity and reliability of the received signal could be better guaranteed. Figure 18 shows the effect of the vertical distance between the OAU and the balise on the uplink received signal power. The closer the vertical distance between the OAU and the balise, the narrower the main lobe width of the displacement-power curve, but the larger the peak power of the main lobe and the side lobe. Within the allowable range of the functional specification, the uplink received signal power with the minimum vertical distance was 13.85 dB higher than that with the maximum vertical distance. However, the null distance was 278 mm smaller. Therefore, many factors should be considered in setting the vertical distance between these antennas. The influence of the lateral deviation of the OAU on the uplink signal power is discussed in Figure 19. According to the engineering experience, the lateral deviation between the OAU and the balise allowed by the manufacturer was generally within 100 mm. The lateral deviation of the antennas did not affect the envelope shape of the displacement-power curve in these ranges. During the lateral shift from 0 to 100 mm, the signal power at each point of the curve along the OX axis decreased by about 1.5 dB. When the lateral deviation was increased to 150 mm, the signal power decreased by about 3.2 dB. The influence of the uplink transmitting current of the active balise on the uplink received signal power is discussed in Figure 20. When the transmitting current on the balise remained constant throughout the uplink signal transmission, the magnitude of the transmitting current did not change the envelopment shape of the displacement-power curve, but was only proportional to the power of the curve at each point along the OX axis. Figure 21 shows the effect of the current intensity of the 27 MHz tele-powering signal on the uplink received signal in the system composed of the OAU and passive balise. \(i_{1}\) represents the displacement-power curve of the uplink received signal of the BTS composed of active balise, and the uplink transmitting current intensity of the balise was set to the current intensity when the passive balise represented by (20) reached a stable  
Figure 22: Variation of uplink received signal power with different installation modes (passive balise). working state. According to the requirements for tele-powering field conformity test in the specification, the current intensities of 27 MHz tele-powering signals were all within the allowable range.