Sub-Sample Dither Removal for Low-Detectability RF Signals
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Solution Overview
Problem
Existing communication systems face challenges in reducing the cyclostationary properties of transmitted waveforms, which can lead to detection and interception, particularly in military applications, as conventional methods either degrade demodulation performance or require high sample rates and complex radio systems.
Innovation Solution
The implementation of a sub-sample dithering technique using polyphase resampling filters at the transmitter to modify sample timing, allowing for time advances or retardations in the discrete-time IF signal, thereby reducing cyclostationary features without significantly degrading Bit Error Rate (BER) performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If conventional methods are used to reduce cyclostationary properties, then detection probability decreases, but demodulation performance degrades
Solution Approach 1:
The patent applies parameter changes by modifying the sample timing parameters of the discrete-time IF signal. Specifically, it introduces time advances or retardations to sample instances, which alters the cyclostationary properties of the transmitted waveform while preserving the underlying modulation structure. This allows reduction in detection probability without significantly degrading BER performance
Solution Approach 2:
The patent employs dynamics by making the sample timing flexible and adjustable rather than fixed. The system dynamically modifies sample durations and introduces time variations (advances/retardations) to eliminate cyclostationary features. This dynamic approach allows the system to adaptively reduce detectability while maintaining communication reliability
2Object-affected harmful factors
If high sample rates are used to reduce cyclostationary properties, then detection probability decreases, but device complexity increases
Solution Approach 1:
The patent changes the timing parameters of existing samples rather than increasing the sample rate. By introducing time advances or retardations to sample instances and modifying sample durations, the system achieves cyclostationary property reduction without requiring higher sampling frequencies, thus avoiding increased radio system complexity
Solution Approach 2:
The patent segments the sample sequence and applies different time modifications to different samples. By processing samples in segments and applying selective time advances or retardations, the system achieves the desired effect without requiring a complete system redesign or high-speed processing infrastructure
3Object-affected harmful factors
If sample timing is modified to reduce cyclostationary features, then detection probability decreases, but processing complexity increases
Solution Approach 1:
The patent modifies timing parameters (sample durations and time instances) rather than changing the fundamental signal processing architecture. This approach reduces processing complexity compared to complete waveform regeneration, as it only requires adjusting temporal parameters of existing samples through techniques like polyphase resampling filters or sample dropping/repeating
Data Source
AI summary
Systems (400) and methods for removing dither introduced into a transmitted RF signal. The method comprising: receiving, by a receiver, the transmitted RF signal; converting, by the receiver, the transmitted RF signal into a discrete-time IF signal comprising a sequence of samples, where at least a first sample of said samples has a first sample duration different than a second sample duration of at least a second sample of said samples; and performing operations by a sub-sample dither removal device of the receiver to modify a sample timing of the discrete-time IF signal by decreasing or increasing the first sample duration of the first sample using a digital signal processing technique in a digital domain.