In the evolving landscape of wireless communication and security, the proliferation of unmanned aerial vehicles (UAVs) has necessitated robust countermeasures. As an engineer focused on射频 front-end design, I embarked on developing a high-efficiency, multi-frequency power amplifier (PA) specifically tailored for anti-drone applications. The core challenge lies in creating a single amplifier that can simultaneously operate across distinct frequency bands—1.5 GHz, 2.4 GHz, and 5.8 GHz—to effectively jam or spoof drone control and navigation signals. Traditional approaches using reconfigurable switches fall short in power handling and concurrent multi-band operation. Therefore, my design leverages advanced dual-band and tri-band matching theories to achieve simultaneous performance at these frequencies, with a frequency ratio exceeding 3.6 and output power above 39 dBm. This capability is critical for portable, integrated anti-drone devices that require high efficiency and compact form factors to neutralize rogue drones in various scenarios.
The foundation of my design rests on extending established dual-band matching principles to a tri-band framework. For the anti-drone system, the frequencies of interest are 1.5 GHz (often used for GPS/GNSS spoofing), 2.4 GHz (common for Wi-Fi and drone control links), and 5.8 GHz (used in higher-bandwidth drone communications). To address this, I first developed a dual-band matching network for the 2.4 GHz and 5.8 GHz bands, then integrated matching for 1.5 GHz without disrupting the existing structure. The output matching network employs a Π-type configuration, which is mathematically elegant and practical for implementation.
Let me detail the theoretical underpinnings. For dual-band matching at frequencies \( f_2 \) (2.4 GHz) and \( f_3 \) (5.8 GHz), the optimal load impedances are denoted as \( Z_2 = R_2 + jX_2 \) and \( Z_3 = R_3 + jX_3 \), respectively. The goal is to transform these to a common real impedance \( Z_S \) (typically 50 Ω) using a transmission line section and Π-network. The initial step involves a transmission line with characteristic impedance \( Z_a \) and electrical length \( \theta_a \) to make the impedances at \( f_2 \) and \( f_3 \) conjugate. The formulas are derived from transmission line theory:
$$ Z_a = \sqrt{R_2 R_3 + X_2 X_3 + \frac{X_2 + X_3}{R_3 – R_2} (R_2 X_3 – R_3 X_2) } $$
$$ \theta_a = \arctan\left( \frac{Z_a (R_3 – R_2)}{R_3 X_2 – R_2 X_3} \right) + n\pi, \quad n = 0, 1, 2, \dots $$
Following this, a Π-network consisting of stubs and series lines achieves the dual-band match. The parameters include \( Z_b \), \( Z_c \), and electrical lengths \( \theta_{T2} \) and \( \theta_{T3} \), with \( \theta_{T2} + \theta_{T3} = \pi \). The design equations are:
$$ Z_T = \sqrt{ \frac{X_a^2 \cdot Z_S}{R_a – Z_S} + R_a \cdot Z_S } $$
$$ \theta_{T2} = \arctan\left( \frac{Z_T \cdot (R_a – Z_S)}{X_a \cdot Z_S} \right) + n\pi $$
$$ Z_b = \frac{Z_T \sin \theta_{T2}}{\sin \theta_2} $$
$$ Z_c = \frac{\tan \theta_2 \cdot Z_b \cdot \sin \theta_2}{\cos \theta_2 – \cos \theta_{T2}} $$
Here, \( \theta_2 \) is defined relative to \( f_2 \), and \( R_a + jX_a \) is the impedance after the initial line. For the tri-band extension to include \( f_1 = 1.5 \) GHz, I introduced additional open- and short-circuited stubs along with a series microstrip line. These elements present high impedance at \( f_2 \) and \( f_3 \), thus preserving the dual-band match while adjusting the admittance at \( f_1 \). The admittance at point B for \( f_1 \) is \( Y_B = G_B + jB_B \). By adding a series line with impedance \( Z_f \) and length \( \theta_f \), and parallel stubs \( Z_{go} \), \( Z_{gs} \), \( Z_{do} \), \( Z_{ds} \), the design ensures \( Y_B \) transforms to \( Y_S = 1/Z_S \). Key formulas include:
$$ \theta_2 = \frac{(1+n)\pi}{1 + (f_3 / f_2)}, \quad n = 0,1,2,\dots $$
$$ Z_{go} = Z_{gs} \tan^2 \theta_2 $$
$$ Z_{do} = Z_{ds} \tan^2 \theta_2 $$
$$ \theta_f = \arctan\left( \frac{Z_S B_3 \pm \sqrt{Z_S G_3 (1 – 2Z_S G_3 + Z_S^2 B_3^2 + Z_S^2 G_3^2)}}{Z_S^2 B_3^2 + Z_S^2 G_3^2 – Z_S G_3} \right) $$
$$ Z_{go} = \frac{\tan^2 \theta_2 \cos\left( \frac{f_1}{f_2} \theta_2 \right) – \tan\left( \frac{f_1}{f_2} \theta_2 \right)}{B_4} $$
Where \( B_4 \) is derived from circuit analysis. This mathematical framework enabled me to synthesize compact matching networks suitable for anti-drone hardware where space and efficiency are paramount.
For the active device, I selected the CGH40010 GaN HEMT from Cree Inc., due to its accurate model, broad bandwidth (500 MHz to 6 GHz), and high-power capability—essential for jamming signals in anti-drone systems. The bias point was set at \( V_{ds} = 28 \) V and \( V_{gs} = -2.75 \) V for optimal performance. Stability was ensured using a stabilization network with a parallel RC (47 Ω, 1.4 pF) and a series microstrip line (30.6 Ω, 52.57° at 2.4 GHz), achieving unconditional stability across all three bands. Load-pull and source-pull simulations in ADS were conducted to extract the optimal impedances for maximum output power and efficiency, critical for effective anti-drone operation. The results are summarized in Table 1.
| 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 these impedances, I computed the parameters for both input and output tri-band matching networks. The output matching network structure is illustrated conceptually, with calculated values provided in Table 2. This network is pivotal for delivering high power across bands to disrupt drone communications.
| Branch | Characteristic Impedance \( Z \) (Ω) | Electrical Length \( \theta \) (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 |
The input matching network was designed similarly, employing the tri-band methodology to ensure proper power transfer from the source. Additionally, a tri-band bias circuit was crucial to prevent RF leakage into DC supplies. Instead of a simple quarter-wavelength line, I used a T-type microstrip structure with multiple stubs to present high impedance at all three frequencies, enhancing stability in harsh anti-drone environments. The bias network comprises sections with \( Z = 50 \) Ω and carefully chosen lengths to act as RF chokes.
With the circuits designed, I performed extensive simulations in ADS to validate performance. The scattering parameters for the input and output matching networks showed excellent return loss and transmission characteristics at the target frequencies. The tri-band bias circuit effectively blocked RF across the spectrum. Most importantly, large-signal simulations revealed the PA’s capability under realistic anti-drone scenarios. With an input power of 28 dBm, the output power and power-added efficiency (PAE) were measured. The results, summarized in Table 3, demonstrate the amplifier’s suitability for anti-drone systems requiring sustained high-power jamming.
| 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 PAE exceeding 60% at 2.4 GHz is particularly notable, as it reduces thermal load and power consumption in field-deployable anti-drone units. The gain remains above 11 dB across bands, ensuring sufficient signal amplification for effective suppression or spoofing. These metrics align with international standards like FCC and CE, enabling the amplifier to be integrated with directional antennas for targeted drone neutralization. The design supports single-, dual-, and tri-band modes, offering flexibility in diverse anti-drone operations.
In conclusion, my work presents a comprehensive design methodology for a tri-band power amplifier that addresses the growing demands of anti-drone technology. By innovatively applying dual-band and tri-band matching theories, I achieved simultaneous high-efficiency operation at 1.5, 2.4, and 5.8 GHz—key frequencies for countering UAV threats. The amplifier delivers over 39 dBm output power with PAE up to 60%, making it ideal for portable, high-performance anti-drone devices. This advancement not only enhances jamming effectiveness but also promotes system integration and cost reduction, contributing to safer airspace in civilian and security applications. Future iterations could explore wider bandwidths or higher power levels to counter evolving drone technologies, solidifying the role of such amplifiers in next-generation anti-drone defenses.