DSSS Transmitter and Receiver for Narrowband Transmission
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Solution Overview
Problem
Existing DSSS transmission systems face challenges in accommodating both broadband and narrowband transmission requirements due to differing legal frameworks across countries, necessitating separate transmitters and receivers, which increases complexity and costs.
Innovation Solution
A DSSS transmission system that can be configured for both spread spectrum and narrowband data transmission by using a DSSS transmitter and receiver with a filter having an impulse response dependent on the chip sequence, allowing for adjustable chip sequences that enable either broadband or narrowband operation without switching between different receiver types.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If separate transmission systems are used for broadband and narrowband transmission to meet different legal frameworks, then compliance with regional regulations is achieved, but device complexity and costs increase
Solution Approach 1:
The patent implements a universal DSSS transmission system that can operate in both broadband spread spectrum mode and narrowband mode by configuring the chip sequence properties. The system uses a single DSSS transmitter and receiver architecture that adapts to different transmission modes through parameter configuration, eliminating the need for separate transmission systems for different regional regulations.
Solution Approach 2:
The system dynamically switches between broadband and narrowband operation by changing the chip sequence characteristics. The chip sequence is configured to produce either wide bandwidth spread spectrum signals or narrowband signals with reduced bandwidth, allowing the system to adapt its spectral characteristics based on the required transmission mode and regional requirements.
2Reliability
If conventional FSK modulation is used for narrowband transmission, then implementation simplicity is maintained, but sensitivity is limited
Solution Approach 1:
The patent improves reception sensitivity by changing the fundamental transmission approach from conventional FSK to narrowband DSSS. By configuring the chip sequence to have restricted sign changes and using a matched filter with corresponding impulse response, the system achieves up to 7dB sensitivity improvement while maintaining a single receiver architecture that can handle both broadband and narrowband modes.
3Adaptability or versatility
If DSSS is used for frequency spreading to meet power distribution requirements, then transmission power distribution over larger bandwidth is achieved, but narrowband transmission capability is lost
Solution Approach 1:
The transmitter dynamically adjusts its operation by changing the chip sequence configuration. For broadband transmission, a conventional spread spectrum chip sequence is used. For narrowband transmission, the chip sequence is configured with restricted sign changes to produce narrowband signals. This dynamic reconfiguration allows the same DSSS transmitter to meet different power distribution requirements in different countries.
Solution Approach 2:
The system applies different chip sequence properties locally depending on the transmission mode required. The chip sequence is designed with specific properties (number of sign changes, transition patterns) that are locally optimized for either broadband or narrowband operation, allowing the transmitter to provide appropriate spectral characteristics for each transmission scenario.
Data Source
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Figure 2(b)~2(c)
Figure 3(a)~3(b)
AI summary
A system is described that can be configured for a spread spectrum and for narrowband data transmission. The system has a DSSS transmitter that is designed to convert a bit string that is to be transmitted into a chip string using a chip sequence and to send a string of impulses corresponding to the chip string. The system also has a DSSS receiver that is designed to receive, via a transmission channel, impulses sent by the transmitter and to filter the received impulses using a filter, wherein the filter has an impulse response that is dependent on the chip sequence. For the spread spectrum data transmission, the chip sequence that can be set is a spread sequence. For the narrowband data transmission, a chip sequence and a corresponding impulse response for the filter can be set, wherein the chip sequence does not comprise a string having two directly successive arithmetic sign changes and, furthermore, an arithmetic sign change occurs neither after the first nor before the last chip in the chip sequence.