Nulling Antenna Jammer Cancellation via Signal Subtraction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing RF interference cancellation techniques, such as directional antennas, may not provide sufficient performance to overcome the effects of jammers, especially in military applications where effective communication is critical.
Innovation Solution
A communication system utilizing a nulling antenna oriented to place a null in the direction of the desired communication signal, combined with a Division Free Duplex (DFD) RF canceller, which processes both omnidirectional and nulling antenna signals to effectively cancel jammer signals, achieving superior jamming suppression.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If directional antennas are used for RF interference cancellation, then some level of jammer suppression is achieved, but the performance is insufficient to overcome the effects of jammers in military applications
Solution Approach 1:
The system segments the antenna function into two specialized components: an omnidirectional antenna for receiving desired signals and a nulling antenna for receiving jammer signals. This segmentation allows each antenna to be optimized for its specific function, with the nulling antenna creating a directional null toward the jammer while the omnidirectional antenna maintains full coverage for legitimate communications.
Solution Approach 2:
The nulling antenna implements local quality by creating a highly directional radiation pattern with a deep null (30 dB gain) specifically oriented toward the jammer's location. This localized directional characteristic allows the system to suppress interference from a specific direction while maintaining omnidirectional reception capabilities through the other antenna.
2Object-affected harmful factors
If a nulling antenna with 30 dB gain is used to achieve superior jamming cancellation, then jammer-to-desired-signal ratio is improved to at least 4 dB, but the system complexity increases due to multiple antennas and signal processing requirements
Solution Approach 1:
The system merges the outputs of two antennas with different radiation patterns through a combining network that performs signal subtraction. The omnidirectional antenna output and the nulling antenna output are combined in a way that cancels the jammer signal while preserving the desired signal, achieving interference cancellation through constructive and destructive interference of the combined signals.
Solution Approach 2:
A directional coupler is introduced as an intermediary component to extract a portion of the signal from the nulling antenna for processing. This coupler enables the system to tap into the jammer signal path without disrupting the main signal flow, allowing for adaptive processing and cancellation while maintaining the integrity of the original signal paths.
3Object-affected harmful factors
If the nulling antenna is oriented to place a null in the direction of the desired communication signal, then jammer signals are cancelled, but the desired signal within the null direction may be affected
Solution Approach 1:
The system uses the nulling antenna's directional null as a counterweight against the jammer signal. By orienting the null toward the jammer's location, the system creates an opposing force that cancels the harmful interference. The omnidirectional antenna simultaneously provides the desired signal that would otherwise be blocked by the null, effectively counterbalancing the signal loss in the null direction.
Solution Approach 2:
The system exploits the asymmetric radiation patterns of the two antennas to its advantage. The nulling antenna has a highly asymmetric pattern with a deep null in the jammer direction, while the omnidirectional antenna has a symmetric pattern that receives signals equally from all directions. This asymmetry allows the system to selectively cancel jammer signals while preserving desired signals through the complementary omnidirectional 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
This approach achieves superior jamming cancellation with a 30 dB gain nulling antenna, providing an effective jammer-to-desired-signal ratio of at least 4 dB, effectively minimizing interference and maintaining communication integrity.
Implementation Method 1
the auxiliary antenna is selected to exhibit a null in its antenna pattern. The null is directed toward the desired signal such that any signals outside of a predetermined angle from the center of the null will be cancelled
Implementation Method 2
The de-multiplexed output from the notched antenna is directly subtracted from the de-multiplexed output from the omnidirectional antenna
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
A communication system includes an omnidirectional antenna 82 to receive a wideband primary signal, a nulling antenna 84 to receive a secondary signal and a controller 86. The nulling antenna 84 is oriented to place a null in a direction of a desired communication signal and the controller 86 subtracts a processed secondary signal from a processed wideband primary signal to produce a jamming cancelled signal.