In recent years, the proliferation of micro-small fixed-wing drones on the battlefield has presented unprecedented challenges to air defense systems. These drones are capable of executing reconnaissance, precision strikes, and loitering attacks, which demand countermeasures that are both effective and cost-efficient. Among the emerging technologies, high power microwave (HPM) systems stand out due to their speed-of-light engagement, high cost-exchange ratio, and deep magazine capacity. However, the effectiveness of HPM against fixed-wing drones in dynamic flight conditions remains poorly understood. To address this gap, we conducted a series of experimental studies using a narrowband HPM test system to evaluate the disruption of a specific micro-small fixed-wing drone during actual flight. Our goal was to capture real-time flight data and analyze the coupling mechanisms that led to loss of control.
The experiment was performed in an open, unpopulated area to ensure safety. The fixed-wing drone was flown on a pre-planned route at an altitude of approximately 300 meters. When the drone entered the designated engagement zone, the HPM system was triggered to radiate a high-power electromagnetic pulse toward the target. The entire engagement was monitored by radar and electro-optical sensors, and onboard flight data were recorded for post-test analysis. This paper presents the experimental setup, the observed behavioral changes of the fixed-wing drone, and the underlying mechanisms of disruption.
Experimental System and Methodology
The narrowband HPM experimental system consisted of two major subsystems: a target acquisition and tracking subsystem, and an HPM transmitter subsystem. The target acquisition subsystem employed a radar sensor and an electro-optical camera to detect and track the fixed-wing drone. The tracking data were used to align the HPM antenna toward the drone with high accuracy. The HPM transmitter subsystem was based on relativistic vacuum electronics and included a charging power supply, a high-voltage pulse generator (implemented as a Marx generator), an HPM source, a radiating antenna, and supporting control and monitoring equipment.
The high-voltage pulse generator was designed using the Marx generator topology. A simplified circuit diagram is shown in the original publication, where capacitors C1 through Cn are charged to a high voltage and then discharged in series through triggered spark gaps. This configuration produces a high-voltage pulse of several hundred kilovolts. To isolate the charging power supply from the reverse voltage generated during the discharge, we incorporated a protection circuit consisting of high-voltage diodes and resistors. The typical output voltage of the generator ranged from 300 kV to 600 kV, depending on the charging voltage. The output waveform is characterized by a pulse duration on the order of tens of nanoseconds and a rise time of a few nanoseconds.
The HPM source, driven by the Marx generator, produced gigawatt-level microwave pulses in the narrowband (L-band) region. The radiated waveform was monitored using a high-speed oscilloscope with integrated Fourier transform capability, confirming a clean spectrum and stable operation. The antenna was designed to have a high power handling capacity and was maintained under vacuum to prevent breakdown.
| Parameter | Specification |
|---|---|
| Charging voltage range | Up to 50 kV (DC) |
| Output voltage of Marx generator | 300 – 600 kV |
| Pulse duration (FWHM) | ~ 50 ns |
| Radiated peak power | ~ 1 GW |
| Operating frequency band | Narrowband (L-band) |
| Pulse repetition frequency | 1 – 10 Hz (adjustable) |
The relationship between the charging voltage and the Marx generator output was experimentally calibrated using a water load. The results showed a linear dependency, which allowed precise control of the radiated field intensity at the target distance. The typical output pulse from the Marx generator is shown in the original text. The radiated waveform of the HPM system, as captured by a field probe, is also documented. The Fourier transform of the waveform indicated a clean fundamental mode with no significant harmonics.
To quantify the coupling efficiency at the target location, the electric field strength at the drone’s position was estimated using the standard free-space propagation model:
$$ E(r) = \frac{\sqrt{30 P_t G_t}}{r} $$
where \(P_t\) is the transmitted peak power, \(G_t\) is the antenna gain, and \(r\) is the distance from the antenna to the target. For our experimental setup, the antenna gain was approximately 25 dB, and the distance to the drone was about 15 km, resulting in an estimated field strength at the drone location on the order of 1 – 10 kV/m, depending on the specific test conditions.
Experimental Results and Analysis
The onboard flight data recorded by the fixed-wing drone before, during, and after the HPM irradiation provided critical insights into the disruption process. The drone’s altitude, as a function of time, is shown in Figure 1 of the original publication. Before the irradiation, the drone was cruising at a stable altitude of approximately 300 meters. Immediately after the HPM pulse, the altitude began to drop rapidly at a rate of 20 m/s, significantly exceeding the normal descent rate. The drone crashed about 10 seconds after the irradiation, with the crash site located on a hillside about 78 meters below the takeoff point.
The roll angle and pitch angle data further illustrate the sudden loss of control. At the moment of irradiation, the roll angle changed abruptly from 13.6° to 3.9°, then linearly decreased to -14.9°, and eventually to -66.3°, representing a total variation of nearly 80°. Similarly, the pitch angle jumped from -3.8° to 21.5° and then increased to 43.6° before slightly recovering. These rapid and extreme angle changes indicate that the flight controller was sending erroneous commands to the control surfaces, leading to an unstable flight state.
The magnetic heading angle also exhibited periodic fluctuations, suggesting that the drone was spiraling uncontrollably. During the 10-second descent, the heading angle completed about 8 full cycles, which is consistent with a loss of coordinated flight control. The altitude and heading data together confirm that the fixed-wing drone entered a rapid spiral descent immediately after being irradiated.
| Parameter | Before irradiation | After irradiation | Change |
|---|---|---|---|
| Altitude (m) | ~ 300 | ~ 100 (10 s later) | -200 m |
| Roll angle (°) | 13.6 | -66.3 (final) | -79.9° |
| Pitch angle (°) | -3.8 | 37.1 (final) | +40.9° |
| Elevator deflection angle (°) | -5.9 | -25 (locked) | -19.1° |
| Rudder deflection angle (°) | 0.1 | 9.7 → 21.5 (erratic) | +21.4° |
The most revealing data came from the control surface deflection angles. The elevator deflection angle changed abruptly from -5.9° to -25° at the instant of irradiation and remained locked at that value, indicating a classic “jamming” or “latch-up” phenomenon in the servo system. The rudder deflection angle, on the other hand, exhibited complex and irregular variations: it first jumped from 0.1° to 9.7°, then increased to 16.9°, dropped to 9.9°, and finally surged to 21.5°. This erratic behavior suggests that the rudder servo was receiving a sequence of nonsensical commands, likely due to a corrupted control signal from the flight controller.
To understand the coupling path, we analyzed the possible mechanisms. High power electromagnetic pulses can interact with electronic systems through two primary routes: “front-door” coupling via antennas and “back-door” coupling through slots, seams, cables, and apertures. For the fixed-wing drone under test, the front-door coupling would affect the GNSS receiver and the communication datalink. However, since the drone’s GNSS and communication remained functional (data were still being logged and transmitted), we concluded that these subsystems were not critically damaged. The loss of altitude and attitude control, combined with the erratic servo behavior, points toward a back-door coupling mechanism that disrupted the central processing unit (CPU) of the flight control system.
The back-door coupling process can be modeled as a cascade of linear and nonlinear stages. The electromagnetic wave propagates from the HPM antenna to the drone as a plane wave (linear propagation with transfer function H1). It then couples into internal cables through apertures and slots (transfer function H2). The coupled voltage on the cables acts as an interference source to the electronic circuits (transfer function H3). The overall transfer function can be written as:
$$ V_{circuit}(f, \theta, \tau, p) = H_3(f, \theta, \tau, p) \cdot H_2(f, \theta, \tau, p) \cdot E_{incident}(f) $$
where \(f\) is frequency, \(\theta\) is arrival angle, \(\tau\) is pulse width, and \(p\) is polarization. In practice, H2 and H3 are highly nonlinear and depend on the geometry of the drone and the specific cable routing. The pulse interference can cause temporary logic upsets or permanent damage in semiconductor devices. In our experiment, the drone’s flight controller CPU was likely forced into a state where it output random or fixed commands to the servo actuators, resulting in the observed elevator lock and rudder oscillation.
The fact that the elevator remained locked at -25° suggests that the CPU output a constant extreme value, possibly due to a register bit being stuck high or low. The rudder’s non-monotonic behavior might indicate a partial recovery followed by further interference. The overall duration of disruption was about 10 seconds, after which the drone crashed. This time window is consistent with the typical recovery time of a microprocessor from a single-event upset, although in this case the drone never recovered control because the altitude loss was irreversible.
Discussion
The experiment clearly demonstrates that narrowband HPM pulses can effectively disrupt micro-small fixed-wing drones during flight. The disruption mechanism is primarily through back-door coupling to the flight control CPU, leading to loss of attitude control and subsequent crash. The key evidence is the simultaneous lock of the elevator and the erratic behavior of the rudder, which directly caused the drastic changes in pitch and yaw.
Compared to static test results, which often measure voltage or current on individual components, dynamic flight tests provide a more realistic assessment of system-level vulnerability. For example, static tests might indicate that a particular servo is immune to pulse interference, but the overall system might still fail due to CPU upset. Our experimental methodology, which combines in-flight data logging with precise HPM exposure, offers a comprehensive approach to evaluate HPM effects on fixed-wing drones.
From the perspective of HPM system design, the effectiveness against fixed-wing drones validates the potential of narrowband systems for counter-drone applications. The ability to cause rapid, irreversible loss of control from a distance of several kilometers is a significant operational advantage. However, the specific susceptibility of the CPU suggests that future countermeasures might need to consider multiple frequency bands or modulation techniques to target different subsystems within the fixed-wing drone.
Conclusion
In this study, we conducted a dynamic disruption experiment on a micro-small fixed-wing drone using a narrowband HPM experimental system. The results show that after irradiation, the elevator deflection angle jumped from -5.9° to -25° and locked, while the rudder deflection angle exhibited irregular oscillations ranging from 0.1° to 21.5°. These control surface anomalies led to rapid changes in pitch and roll angles, causing the fixed-wing drone to enter a spiral descent and crash within 10 seconds. Analysis of onboard flight data and coupling mechanisms indicates that the flight control CPU was functionally disrupted through back-door coupling, resulting in the output of erroneous commands to the servo actuators.
Our findings highlight the importance of CPU-level hardening for the flight control systems of fixed-wing drones to improve their electromagnetic resilience. They also underscore the value of dynamic flight testing as a critical method for validating the effectiveness of HPM weapons. Future work will focus on real-time monitoring of CPU signals during HPM exposure and exploring multi-physics simulation models to predict the disruption thresholds for various fixed-wing drone configurations.
The experimental methodology and data presented here provide a solid foundation for further research into HPM effects on aerial vehicles, particularly for fixed-wing drones. The narrowband HPM system demonstrated its capability to induce catastrophic failure in the target, reinforcing its potential as a viable countermeasure against the growing threat of fixed-wing drones in modern warfare.