Cross-Polarized GPS Antenna Nulling for Small UAV Interference
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Solution Overview
Problem
Current GPS anti-jam antenna solutions are not suitable for small UAV applications due to size, weight, and power limitations, and they are susceptible to RF emissions that expose UAVs and operators to detection, jamming, and kinetic attacks.
Innovation Solution
A low-profile, lightweight, and resilient GPS antenna assembly is designed for small UAV applications, featuring a two-antenna omni-directional steerable-null phased array with cross-polarized and circularly-polarized antennas. This assembly receives and destructively combines satellite and interfering signals to create a null at or below the horizon, minimizing interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If current GPS anti-jam antenna solutions are used, then interference rejection capability is improved, but size, weight and power increase making them unsuitable for small UAV applications
Solution Approach 1:
The antenna system is segmented into two separate circularly-polarized antennas with opposite polarizations (one facing skyward, one facing groundward), each handling specific signal directions. This segmentation allows the system to achieve anti-jam capabilities through signal combining while keeping individual antenna elements small and lightweight for UAV deployment.
Solution Approach 2:
The patent combines signals from two oppositely-polarized antennas through coherent processing and constructive interference to create a unified reception pattern with enhanced anti-jam performance. By merging the capabilities of both antennas and using phase alignment, the system achieves superior interference rejection without requiring a single large complex antenna structure.
2Measurement precision
If RF emissions are increased for better signal reception, then navigation accuracy is improved, but detection and jamming risk increases
Solution Approach 1:
The antenna system applies different reception characteristics to different spatial directions: the skyward antenna optimizes for satellite signals from above while the groundward antenna handles terrestrial interference from below. This local quality differentiation allows selective signal enhancement and interference suppression in specific directions, improving navigation accuracy while minimizing overall RF emission exposure.
Solution Approach 2:
The system converts the presence of interfering signals into a beneficial effect by using the groundward antenna to detect and characterize terrestrial interference, then applying coherent cancellation techniques. The interfering signals are transformed from harmful factors into information that enables active cancellation, improving navigation accuracy while reducing the need for high-power transmission.
3Reliability
If a single high-gain antenna is used, then signal reception is improved, but susceptibility to terrestrial interference increases
Solution Approach 1:
The patent employs asymmetric antenna placement and polarization: one antenna is oriented skyward with polarization optimized for satellite signals, while the other faces groundward with polarization optimized for terrestrial interference. This asymmetric configuration allows the system to preferentially receive desired satellite signals while rejecting terrestrial interference through polarization filtering and spatial separation.
Solution Approach 2:
The system adds the dimension of polarization to the traditional spatial antenna arrangement. By utilizing orthogonal circular polarizations in addition to vertical spatial separation (skyward vs. groundward orientation), the system creates a two-dimensional rejection space that effectively filters terrestrial interference while maintaining satellite signal reception.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The antenna assembly effectively minimizes undesired on-air signals, providing reliable GPS navigation for small UAVs while adhering to size, weight, and power constraints, and it supports Group 1 SUAS operations by creating a null near the horizon, reducing interference from terrestrial signals.
Implementation Method 1
a first polarized antenna disposed on the antenna reflector and having a first polarization; a second polarized antenna disposed on the antenna reflector and having a second polarization opposite to the first polarization
Implementation Method 2
generating a second signal by shifting a phase of the interfering signal which was received at the second polarized antenna by an amount to cause the second signal to be out-of-phase with the first signal
Implementation Method 3
providing an antenna pattern with a null at or below a horizon by destructively combining the second signal with the first signal
Data Source
AI summary
Systems and methods for operating an antenna assembly. The methods comprise: receiving, at the first polarized antenna, a first signal comprising a desired signal emitted from a first signal source located at a first altitude higher than a second altitude of the antenna assembly and an interfering signal emitted from a second signal source located at a third altitude lower than the second altitude; receiving the interfering signal at the second polarized antenna (where the first and second polarized antennas have opposite circular polarizations); generating a second signal by shifting a phase of the interfering signal which was received at the second polarized antenna by an amount to cause the second signal to be out-of-phase with the first signal; and providing an antenna pattern with a null at or below a horizon by destructively combining the second signal with the first signal.