Filter-Bank Multi-Carrier Spread Spectrum Signal Design
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Solution Overview
Problem
Conventional multi-carrier spread spectrum techniques are susceptible to narrow and partial band interference, and they require higher power levels, making them less effective in harsh RF environments and less efficient in spectrum usage.
Innovation Solution
The use of Filter-Bank Multi-Carrier Spread Spectrum (FB-MC-SS) signals, which operate at or below noise levels, utilize non-overlapping subcarrier filters to coexist with other signals, and feature redundant data symbol transmission, allowing them to resist interference and operate in harsh conditions without disrupting existing spectrum use.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional multi-carrier spread spectrum techniques are used, then data transmission can be achieved, but the system is susceptible to narrow and partial band interference and requires higher power levels
Solution Approach 1:
The patent divides the frequency spectrum into multiple non-overlapping subcarrier bands, with each band carrying a portion of the spread spectrum signal. This segmentation allows the system to distribute power across multiple frequency segments, reducing the power level required in each individual band while maintaining overall transmission reliability and resistance to narrowband interference.
Solution Approach 2:
The patent employs filter bank multi-carrier modulation to transform the conventional OFDM signal into a spread spectrum signal by applying specific filtering operations. This changes the spectral characteristics of the signal, distributing energy more uniformly across the frequency spectrum and reducing peak power requirements while enhancing resistance to narrowband interference through the spread spectrum effect.
2Difficulty of detecting and measuring
If conventional spread spectrum techniques are used, then communication can be established, but the signals are more detectable and consume more power
Solution Approach 1:
The patent transmits spread spectrum signals at power levels at or below the noise floor in each individual subcarrier band. By using partial action (transmitting below full power) across multiple bands simultaneously, the system achieves low detectability in each band while maintaining reliable communication through the cumulative effect across all bands, thus reducing both detection probability and power consumption.
3Reliability
If higher power levels are used in multi-carrier spread spectrum, then signal transmission can be maintained, but spectrum usage efficiency decreases and interference susceptibility increases
Solution Approach 1:
The patent segments the transmitted signal across multiple non-overlapping subcarrier bands using filter bank modulation. This allows the system to maintain signal transmission stability through distributed transmission while improving spectrum usage efficiency by utilizing available frequency resources more effectively and reducing vulnerability to narrowband interference through diversity across multiple segments.
Data Source
AI summary
A transmitter includes a synthesis filter bank to spread a data symbol to a plurality of frequencies by encoding the data symbol on each frequency, apply a common pulse-shaping filter, and apply gains to the frequencies such that a power level of each frequency is less than a noise level of other communication signals within the spectrum. Each frequency is modulated onto a different evenly spaced subcarrier. A demodulator in a receiver converts a radio frequency input to a spread-spectrum signal in a baseband. A matched filter filters the spread-spectrum signal with a common filter having characteristics matched to the synthesis filter bank in the transmitter by filtering each frequency to generate a sequence of narrow pulses. A carrier recovery unit generates control signals responsive to the narrow pulses suitable for generating a phase locked loop between the demodulator, the matched filter, and the carrier recovery unit.