By Dustin Guttadauro, Product Line Manager - Telecom & Fiber, Infinite Electronics
Autonomous loitering munitions operate at the edge of the RF link budget. Unlike traditional UAVs, these systems rely on continuous, high-integrity GNSS positioning throughout dynamic flight profiles, including high-speed terminal dives.
The challenge is that Global Navigation Satellite System (GNSS) signals arrive at extremely low power levels—often near the noise floor. Any additional loss introduced by internal cabling, connectors or onboard interference can push the signal below the receiver’s usable threshold.
Active GNSS architectures address this constraint by amplifying the signal at the antenna before it enters the airframe. Combined with low-loss cabling and proper RF design, this approach ensures consistent satellite lock and accurate terminal guidance.
Key Takeaways
- GNSS signals arrive at extremely low power levels and are highly susceptible to insertion loss
- Active antennas compensate for cable and connector losses by amplifying signals at the source
- Higher signal-to-noise ratio (SNR) improves lock stability in noisy UAV environments
- Phase and signal integrity must be preserved through high-quality coaxial cabling
- Reliable GNSS is critical for terminal accuracy and minimizing Circular Error Probable (CEP)
The RF Budget Crisis in Loitering Munitions
GNSS signals reaching a UAV are extremely weak, typically around -130 dBm. This leaves very little margin for loss within the system.
Every connector, adapter and length of cable reduces signal strength further. In compact or complex airframes, cumulative insertion loss can quickly degrade the signal to the point where the receiver struggles to maintain lock.
This is especially problematic during dynamic maneuvers, where antenna orientation and environmental factors already stress signal acquisition. Without compensation, passive systems often fail to maintain consistent positioning.
Solving for Accuracy: LCANGPS1009 Active Antenna
Active GNSS antennas address this limitation by integrating a Low Noise Amplifier (LNA) directly at the antenna element.
The LCANGPS1009 provides approximately 10 dBic of gain using circular polarization, aligning with GNSS satellite transmission characteristics. This amplification occurs before signal loss is introduced by downstream components, effectively preserving usable signal strength.
In addition to amplification, active antennas incorporate filtering to reject out-of-band interference. This prevents elevation of the noise floor and improves overall receiver performance in electrically noisy environments.
Preserving the Gain: LCCA30011 Coaxial Cable
Amplifying the signal at the antenna is only effective if that signal is preserved along the transmission path.
Low-loss coaxial cables such as the LCCA30011 minimize attenuation between the antenna and receiver. Their construction reduces dielectric and conductor losses while maintaining consistent impedance.
Shielding is equally important. UAV airframes contain multiple sources of electromagnetic interference, including motors, power electronics and radios. High-shielding cable assemblies prevent this interference from coupling into the GNSS signal path.
By maintaining both amplitude and signal purity, the system ensures that the receiver benefits fully from the antenna’s active gain.
Why is GNSS integrity critical for last-mile autonomous flight?
During terminal flight, loitering munitions experience rapid changes in orientation and high dynamic loads.
If GNSS lock is lost during this phase, the system may revert to dead reckoning or inertial navigation, which introduces cumulative error. This can significantly increase Circular Error Probable (CEP) and reduce targeting effectiveness.
Maintaining continuous satellite visibility ensures that the munition receives real-time positional updates, enabling precise corrections throughout the final approach.
Active GNSS systems provide the sensitivity and stability required to maintain this lock under worst-case conditions.
Implementation in High-Vibration Airframes
Mechanical and electrical integration must support the demands of high-speed, high-vibration environments.
The antenna must be securely mounted to maintain consistent orientation and electrical contact with the airframe. Poor mounting can introduce additional loss or intermittent performance issues.
Cable routing is equally critical. GNSS cables should be physically separated from high-current power lines and switching electronics to reduce EMI coupling. Using high-shielding cables such as LCCA30011 helps further isolate the signal path.
System-level EMI mapping can identify potential interference sources and guide optimal component placement.
L-com’s broad selection of GNSS antennas and RF interconnect solutions supports reliable navigation performance in demanding UAV applications. For minimal downtime and rapid deployment, we ship quickly, with same-day shipping on qualified in-stock online orders placed Monday through Friday before 5 p.m. EST.
Frequently Asked Questions (FAQ)
Why is a passive GNSS antenna insufficient for loitering munitions?
Passive antennas rely entirely on the incoming signal strength. In systems with long cable runs or multiple interconnects, insertion loss can reduce signal levels below the receiver’s sensitivity threshold. Active antennas amplify the signal at the source, preserving usable signal strength throughout the system.
Does an active GNSS antenna improve resistance to jamming?
Active antennas do not eliminate jamming, but they improve resilience by increasing the strength of legitimate satellite signals and filtering out-of-band interference. This raises the effective signal-to-noise ratio, making it more difficult for low-level interference to disrupt positioning.
What does 10 dBic gain indicate in a GNSS antenna?
dBic refers to gain relative to an isotropic circularly polarized reference antenna. A 10 dBic antenna is optimized to receive circularly polarized GNSS signals efficiently, improving signal acquisition and stability regardless of UAV orientation.
How does cable selection impact GNSS performance in UAVs?
Cable loss directly reduces signal strength between the antenna and receiver. Poor shielding can also introduce interference from onboard systems. Using low-loss, high-shielding cables ensures that amplified signals remain intact and free from noise as they travel through the airframe.
