Simulation Research on the Effect of Ultra-wideband Pulses with a Global Positioning System Antenna

With the development of drone technology, drones are gradually being applied in various industries. But with the increasingly complex electromagnetic environment, the impact of electromagnetic interference on drones is also gradually increasing. The GPS is one of the important components of unmanned aerial vehicles. This paper establishes a 1.58 GHz frequency band circularly polarized microstrip patch antenna model. It uses this model to simulate the coupling effect of UWB pulses on the front door of the GPS. UWB pulses with different polarization directions and incidence angles were selected for coupling simulation research. The results indicate that the coupling effect is closely related to the polarization direction and incident direction angle of the pulse, and the coupling signal spectra under different conditions are obtained. This result guides subsequent experiments on the coupling effect of UWB pulses on unmanned aerial vehicles and research on the coupling mechanism.


INTRODUCTION
Drones are becoming increasingly prevalent as technological advancements to drive their applications forward [1] .However, their heavy reliance on electronics makes them highly susceptible to electromagnetic interference (EMI) [2] .In complex electromagnetic environments, the sudden and intense energy of strong electromagnetic pulses (EMPs) can significantly damage the electronic equipment and systems onboard [3] .As a result, there is a compelling need to investigate the interaction between powerful EMPs and the electronic components and systems found in UAVs.The GPS is one of the important components of unmanned aerial vehicles, playing an important role in positioning and maintaining flight attitude [4] .The coupling between strong electromagnetic pulses (EMPs) and UAV electronic equipment primarily occurs through the front door, which involves the interaction between the EMP and the antenna.This article focuses on investigating the specific coupling effect associated with the front door and developing an electromagnetic model for a circularly polarized microstrip patch antenna operating within the 1.58 GHz frequency range.The coupling effect of UBW pulses is simulated using this model, and the influence of different polarization directions and incidence angles of UWB pulses on the coupling effect is obtained.

ESTABLISHMENT OF ANTENNA MODEL
The GPS antenna usually uses a circularly polarized Microstrip antenna, formed by the position of the feed point and the chamfer form on the patch.By commonly encountered application scenarios, electromagnetic simulation software was employed to design a circularly polarized microstrip patch antenna tailored for the 1.58 GHz frequency band [7][8][9][10] .The resulting design is illustrated in Figure 1.Gaussian double pulse, and its function expression is [5][6] : is the width between positive and negative peaks of the Gaussian double pulse signal.This article uses a first-order Gaussian pulse as the radiation source and emits radiation waves through plane wave radiation.Figure 3 shows that the positive and negative peak bandwidth of the Gaussian double signal is 300 ps, and its spectrum is shown in Figure 4.

Simulation of the Response to the Pulse of Different Incident Directions and Polarization Angles
Using UWB pulses as the source of interference, we simulate the coupling voltage waveforms in different incident directions when the polarization direction is not aligned with the offset direction of the feed port, as shown in the Figure 5.We set the incident direction angles to 0°, 45°, and 90°.T The electric field value of UWB pulses is always maintained at 1 V/m.The coupling outcomes are depicted in Figure 6, revealing a correlation between the incident direction angle and the peak coupling voltage.As the incident direction angle increases, the peak coupling voltage increases significantly.Specifically, the coupling voltage reaches its minimum when the incident direction is horizontal, while it attains its maximum when vertical.The peak value of the coupling voltage is the negative cubic order of ten of the peak value of the interference pulse.The spectrum of the coupled signal is shown in Figure 7.In addition to the 1.6 GHz frequency band, many waveforms from other frequency bands are also coupled, which leads to an increase in the peak-to-peak values of the waveform.The electric field value of UWB pulses is always maintained at 1 V/m. Figure 9 presents the coupling results, indicating a positive relationship between the incident direction angle and the peak coupling voltage.As the incident direction angle increases, the peak coupling voltage progressively rises.Notably, the smallest coupling voltage is observed when the incident direction is horizontal, while the maximum coupling voltage occurs when the incident direction is vertical.Unlike the previous text, the peak value of the coupling voltage is a negative fourth power order of 10 times the peak value of the interference pulse.The spectrum of the coupled signal is shown in Figure 10.Unlike the previous section, the spectrum energy in this polarization direction is concentrated in two frequency bands: 1.6 GHz and 2.4 GHz.As the incident direction angle increases, the ratio of the energy of the two frequency bands also increases.When the incident angle is horizontal, the energy of the 2.4 GHz frequency band is close to half of the energy of the 1.6 GHz frequency band.When the incident angle is vertical, almost all energy is concentrated in the 1.6 GHz frequency band.

CONCLUSION
This paper simulates the coupling response of GPS antennas in the 1.58 GHz frequency band under different polarization directions and incident angles of UWB pulse radiation.The simulation results demonstrate how the coupling effect is affected by varying polarization directions and incident angles.These findings shed light on the relationship between these factors and their impact on coupling behavior.The simulation results indicate that the GPS antenna exhibits excellent circular polarization performance within the 1.6 GHz band.However, in other frequency bands, the polarization characteristics tend to approach linear polarization rather than circular.And the incident angle affects the coupling energy and changes the spectral distribution of the coupling signal.The findings of this paper carry significant practical implications for on-site testing related to the coupling effects and understanding the front door coupling mechanism of unmanned aerial vehicles (UAVs).This work provides valuable guidance for researchers and practitioners studying and evaluating the coupling effects of UAVs in real-world scenarios.

Figure 9 .Figure 10 .
Figure 10.Waveform of coupled signals Due to differences in polarization direction and incidence angle, there are significant differences in the spectral distribution of coupled signals.