Satellite Jamming Mitigation via OFDM Subcarrier Filtering
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Solution Overview
Problem
Satellite communications are vulnerable to jamming from hostile sources and partial-band interference, which disrupts transmissions and increases with the power of the jamming signal, especially as terrestrial service providers demand a share of the spectrum traditionally used for satellite communications.
Innovation Solution
The system employs orthogonal frequency division multiplexing (OFDM)-like signaling with Scrambled Code Multiple Access (SCMA) to generate a waveform that includes unique words and pilot symbols, allowing data to modulate narrowband subcarriers, and uses notch filters to remove interfering frequency segments, enhancing resilience against jamming.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If partial-band jamming is applied to disrupt satellite communications, then the jamming effectiveness increases with the power of the jamming signal, but the complexity of countermeasures and system resilience worsens
Solution Approach 1:
The patent segments the communication signal into multiple orthogonal subcarriers in the frequency domain. Each subcarrier can be independently affected by jamming, but the receiver can selectively process only the non-jammed subcarriers to recover the transmitted data, thereby countering partial-band jamming without requiring complex overall system changes
Solution Approach 2:
The patent transforms the signal from a single-carrier time-domain signal into a multi-carrier frequency-domain representation using OFDM. This dimensional transformation allows the system to identify and exclude jammed frequency segments while maintaining communication through clean subcarriers, adding a frequency-selective dimension to jamming resistance
2Object-affected harmful factors
If the bandwidth of the jamming signal is increased to cover more of the system bandwidth, then the jamming effectiveness improves, but the loss of information in non-jammed segments worsens
Solution Approach 1:
By dividing the total bandwidth into many narrow orthogonal subcarriers, the patent ensures that even if a wide bandwidth is jammed, only a subset of subcarriers is affected. The receiver can identify which subcarriers remain clean and aggregate their information to reconstruct the transmitted data, minimizing information loss despite extensive jamming
Solution Approach 2:
The patent changes the spectral distribution parameter by spreading data across many narrow subcarriers rather than using a single wide carrier. This parameter change allows the system to tolerate wider jamming bandwidths because the information is distributed across frequency segments that can be selectively discarded if jammed
3Reliability
If orthogonal frequency division multiplexing is used to resist jamming, then the resilience to jamming improves, but the device complexity increases
Solution Approach 1:
The patent replaces complex mechanical or analog frequency-selective filtering mechanisms with digital signal processing operations. The OFDM receiver uses efficient FFT-based algorithms to transform the received signal into the frequency domain, where simple digital filtering can exclude jammed subcarriers without requiring complex hardware
Data Source
AI summary
A transmitter, including a signal processor programmed to generate, based on input serial data, for each of an integer number of subcarriers mutually orthogonal to each other, a respective first parallel data stream. The signal processor is further programmed to modulate each of the integer number of subcarriers respectively with the respective parallel stream to generate the integer number of data-modulated subcarriers. The signal processor is further programmed to modulate a single carrier occupying a same bandwidth as the integer number of subcarriers with a unique word and one or more pilot symbols to generate a second signal. The signal processor combines the first signal and second signal to generate a third signal. The signal processor generates an output signal by applying a transmit filter to the third signal.