In modern wireless communication systems, the demand for multi-band operation has become paramount due to the proliferation of diverse frequency standards and the need for versatile anti-UAV (unmanned aerial vehicle) countermeasures. As UAVs increasingly utilize multiple frequency bands for navigation, control, and data transmission, effective anti-UAV systems must capable of jamming or spoofing signals across these bands simultaneously. This study focuses on the design of a tri-band radio frequency (RF) power amplifier that operates at 1.5 GHz, 2.4 GHz, and 5.8 GHz, specifically tailored for anti-UAV applications. The amplifier enhances signal suppression and deception capabilities in anti-UAV devices, improving efficiency and integration. Below, I present a detailed account of the design methodology, theoretical foundations, simulation results, and applications in anti-UAV systems, utilizing formulas and tables to summarize key aspects.
The evolution of wireless technology has driven the need for components that support multi-mode and multi-band functionality. Power amplifiers, as critical elements in RF chains, face significant challenges in achieving concurrent multi-band operation without compromising performance. Traditional approaches, such as reconfigurable designs using RF MEMS switches, often limit power handling and cannot operate simultaneously across bands. In anti-UAV scenarios, where jamming or spoofing requires high output power across multiple UAV communication frequencies, a tri-band amplifier offers a compact and cost-effective solution. This design targets frequencies commonly used by UAVs: 1.5 GHz for Global Navigation Satellite Systems (GNSS), 2.4 GHz for Wi-Fi and control links, and 5.8 GHz for video transmission. By enabling simultaneous operation, this amplifier can disrupt UAV operations more effectively, aligning with FCC and CE standards for anti-UAV equipment. The core innovation lies in a matching network based on dual-band and tri-band theories, allowing efficient power transfer across a wide frequency ratio exceeding 3.6.
The matching network design is pivotal for achieving tri-band performance. Building on dual-band matching principles, the approach first matches the 2.4 GHz and 5.8 GHz bands using a Π-structure, then incorporates additional elements to include 1.5 GHz without disturbing the dual-band match. For the dual-band segment, consider optimal load impedances at frequencies \(f_2 = 2.4 \, \text{GHz}\) and \(f_3 = 5.8 \, \text{GHz}\), denoted as \(Z_2 = R_2 + jX_2\) and \(Z_3 = R_3 + jX_3\). A transmission line segment with characteristic impedance \(Z_a\) and electrical length \(\theta_a\) transforms \(Z_2\) and \(Z_3\) into conjugate pairs. The parameters are derived as follows:
$$ Z_a = \sqrt{R_2 R_3 + X_2 X_3 + \frac{X_2 + X_3}{R_3 – R_2} (R_2 X_3 – R_3 X_2) } $$
$$ \theta_a = \arctan\left( \frac{Z_a (R_3 – R_2)}{R_3 X_2 – R_2 X_3} \right) + n\pi, \quad n = 0,1,2,\ldots $$
Subsequently, a Π-network with impedances \(Z_b\) and \(Z_c\) and a transmission line \(Z_T, \theta_T\) achieves simultaneous matching at \(f_2\) and \(f_3\). The equations governing this part are:
$$ Z_T = \sqrt{ \frac{X_a^2 Z_s}{R_a – Z_s} + R_a Z_s } $$
$$ \theta_{T2} + \theta_{T3} = \pi $$
$$ \theta_{T2} = \arctan\left( \frac{Z_T (R_a – Z_s)}{X_a Z_s} \right) + n\pi $$
$$ Z_b = \frac{Z_T \sin \theta_{T2}}{\sin \theta_2} $$
$$ Z_c = \frac{\tan \theta_2 \times Z_b \times \sin \theta_2}{\cos \theta_2 – \cos \theta_{T2}} $$
Here, \(Z_s = 50 \, \Omega\) is the source impedance, and \(\theta_2\) is defined relative to \(f_2\) and \(f_3\):
$$ \theta_2 = \frac{(1 + n)\pi}{1 + (f_3 / f_2)}, \quad n = 0,1,2,\ldots $$
After matching \(f_2\) and \(f_3\), the network extends to include \(f_1 = 1.5 \, \text{GHz}\). At point B, the admittance at \(f_1\) is \(Y_B = G_B + jB_B\). To match \(Y_B\) to \(Y_s = 1/Z_s\) without affecting the dual-band match, parallel open- and short-circuited stubs and a series transmission line are added. The stubs \(Z_{go}\), \(Z_{gs}\), \(Z_{do}\), and \(Z_{ds}\) exhibit infinite impedance at \(f_2\) and \(f_3\), ensuring isolation. The key formulas for the tri-band extension are:
$$ Z_{go} = Z_{gs} \tan^2 \theta_2 $$
$$ Z_{do} = Z_{ds} \tan^2 \theta_2 $$
$$ \theta_f = \arctan\left( \frac{Z_s B_3 \pm \sqrt{Z_s G_3 (1 – 2Z_s G_3 + Z_s^2 B_3^2 + Z_s^2 G_3^2)}}{Z_s^2 B_3^2 + Z_s^2 G_3^2 – Z_s G_3} \right) $$
$$ Z_{go} = \frac{\tan^2 \theta_2 \cos\left( \frac{f_1}{f_2} \theta_2 \right) – \tan\left( \frac{f_1}{f_2} \theta_2 \right)}{B_4} $$
In these equations, \(B_4\) is derived from transmission line theory, and \(G_4\) equals \(Y_s\) after optimization. This theoretical framework enables the design of a compact tri-band matching network, crucial for anti-UAV devices where size and efficiency are critical.
The amplifier design employs a GaN HEMT transistor, selected for its broad bandwidth (500 MHz to 6 GHz) and accurate modeling. The static operating point is set at a drain voltage of 28 V and gate voltage of -2.75 V, determined through DC sweep analysis. Stability is ensured using a stabilization circuit with a parallel RC network (47 Ω resistor and 1.4 pF capacitor) and a series microstrip line (30.6 Ω characteristic impedance, 52.57° electrical length at 2.4 GHz), achieving absolute stability across all bands. Load-pull and source-pull simulations with harmonic balance techniques identify optimal impedances for maximum output power and efficiency at each frequency. The results are summarized in Table 1, which guides the matching network synthesis.
| Frequency (MHz) | Load Impedance (Ω) | Input Impedance (Ω) |
|---|---|---|
| 1575 | 22.517 + j10.148 | 32.393 – j2.095 |
| 2438 | 20.465 + j8.503 | 25.236 + j40.207 |
| 5777 | 12.406 – j7.450 | 2.336 – j1.492 |
Using the formulas above, the output matching network is constructed with parameters listed in Table 2. The input matching network follows a similar tri-band structure, computed via analogous methods to ensure conjugate matching at all frequencies. The biasing circuit employs a T-shaped microstrip line design instead of a simple quarter-wavelength line, providing high impedance at 1.5 GHz, 2.4 GHz, and 5.8 GHz to prevent RF leakage into the power supply. This tri-band choke enhances stability and efficiency, which is vital for reliable anti-UAV operation under varying loads.
| Branch | Characteristic Impedance (Ω) | Electrical Length (degrees) |
|---|---|---|
| a | 14.97 | 7.44 |
| b | 30.48 | 53.42 |
| c | 31.48 | 53.42 |
| f | 50.00 | 236.10 |
| go | 61.04 | 53.42 |
| gs | 32.60 | 53.42 |
Simulation trials validate the design using Advanced Design System (ADS) software. The input and output matching circuits exhibit excellent return loss and impedance transformation across the bands, as shown in S-parameter plots. The biasing circuit demonstrates high impedance magnitude at the target frequencies, confirming effective RF choking. Large-signal simulations assess performance under an input power of 28 dBm. The results, summarized in Table 3, highlight the amplifier’s capability for anti-UAV applications, where high output power and efficiency are essential for jamming UAV signals.
| Frequency (GHz) | Output Power (dBm) | Power-Added Efficiency (%) | Gain (dB) |
|---|---|---|---|
| 1.5 | 39.88 | 46.52 | 11.88 |
| 2.4 | 40.94 | 60.54 | 12.94 |
| 5.8 | 39.25 | 39.40 | 11.25 |
The amplifier supports single-band, dual-band, and tri-band modes, with an average gain exceeding 12 dB and power-added efficiency above 40% at 1.5 GHz and 5.8 GHz, and over 60% at 2.4 GHz. These metrics surpass typical requirements for civilian anti-UAV systems, which often demand output powers above 39 dBm to effectively suppress or spoof UAV signals. The design’s wide frequency coverage allows it to target multiple UAV communication channels simultaneously, enhancing the effectiveness of anti-UAV measures. For instance, by jamming GNSS signals at 1.5 GHz, control links at 2.4 GHz, and video feeds at 5.8 GHz, a single device can incapacitate drones across various operational scenarios.
Further analysis involves harmonic balance simulations to evaluate linearity and intermodulation distortion, critical for anti-UAV applications where signal purity can affect jamming precision. The third-order intercept point (IP3) and adjacent channel power ratio (ACPR) are computed using the following general formulas:
$$ \text{IP3} = P_{\text{out}} + \frac{\Delta P}{2} $$
where \(\Delta P\) is the power difference between fundamental and third-order products. For a multi-band amplifier, intermodulation products near UAV frequencies must be minimized to avoid unintended interference. Additionally, thermal simulations ensure reliability under continuous operation, as anti-UAV devices may operate for extended periods. The efficiency values derived here contribute to lower heat dissipation, aligning with compact form factors in portable anti-UAV systems.
The application of this tri-band power amplifier in anti-UAV technology is multifaceted. It can integrated into directed energy weapons or jamming arrays that emit RF signals to disrupt drone navigation and control. By covering key UAV bands, it addresses limitations in single-band jammers that are easily circumvented by frequency-hopping drones. Moreover, the amplifier’s design principles can scaled to other frequency sets, such as those used in military anti-UAV systems, by adjusting the matching network parameters. The use of GaN technology ensures high power density and robustness, suitable for harsh environments encountered in anti-UAV deployments.
In conclusion, this study demonstrates a systematic approach to designing a tri-band power amplifier for anti-UAV applications. The matching network, based on extended dual-band theory, enables simultaneous operation at 1.5 GHz, 2.4 GHz, and 5.8 GHz with high efficiency and output power. Simulations confirm its viability, meeting the demands of signal suppression and spoofing in counter-drone systems. Future work could involve prototyping and field testing to validate performance in real-world anti-UAV scenarios, potentially integrating adaptive algorithms for dynamic frequency targeting. As UAV threats evolve, such multi-band amplifiers will play a crucial role in enhancing anti-UAV capabilities, offering a balance of power, efficiency, and integration.
To further elaborate on the design’s significance, consider the mathematical modeling of power amplifier efficiency in multi-band operation. The overall efficiency \(\eta\) for concurrent multi-band transmission can expressed as a weighted sum of individual band efficiencies:
$$ \eta = \sum_{i=1}^{3} \alpha_i \eta_i $$
where \(\eta_i\) is the efficiency at frequency \(f_i\), and \(\alpha_i\) is the power weighting factor dependent on the anti-UAV jamming strategy. For broad-spectrum jamming, \(\alpha_i\) may equal, but for targeted spoofing, they could vary based on UAV vulnerability analysis. Additionally, the matching network’s bandwidth can analyzed using fractional bandwidth calculations:
$$ \text{FBW} = \frac{f_{\text{high}} – f_{\text{low}}}{f_{\text{center}}} \times 100\% $$
For this design, the ratio \(f_3/f_1 = 5.8/1.5 \approx 3.87\), indicating a wideband capability beneficial for covering diverse UAV frequencies. The table below summarizes key performance comparisons with existing dual-band amplifiers, underscoring advantages for anti-UAV use.
| Design Type | Bands (GHz) | Max Output Power (dBm) | Average Efficiency (%) | Suitability for Anti-UAV |
|---|---|---|---|---|
| Dual-Band (Ref) | 2.4/5.8 | 40.5 | 55 | Moderate |
| Tri-Band (This Work) | 1.5/2.4/5.8 | 40.94 | 48.82 | High |
| Reconfigurable | Switchable bands | 38.0 | 45 | Low (due to sequential operation) |
The integration of such amplifiers into anti-UAV systems reduces device count and cost, as a single unit replaces multiple single-band amplifiers. This is particularly important for mobile anti-UAV platforms, where size and weight constraints are stringent. Furthermore, the design’s scalability allows for adaptation to emerging UAV frequencies, ensuring longevity in evolving anti-UAV landscapes. In summary, this tri-band power amplifier represents a significant advancement in RF technology for anti-UAV purposes, combining theoretical innovation with practical performance metrics.