Direct Sampling Transmitter with Nyquist-Zone Band Selection
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Solution Overview
Problem
Wireless communication systems face challenges in miniaturization and cost reduction due to the need for numerous analog components in radio frequency electronics, especially at higher frequencies, and limitations in digital-to-analog conversions for software-defined radios.
Innovation Solution
A method and system that convert digitized signals to analog signals, enhance them at selected sample rates to form spectrally-enhanced signals, and pass them through selectable bandpass filters to ensure the radio signal is within a Nyquist zone, using a programmable sample clock generator and switching network to select appropriate filters and sample rates for efficient transmission across various frequency bands.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If traditional analog components are used for radio frequency transmission, then signal transmission can be achieved, but the system size, weight, and cost increase significantly
Solution Approach 1:
The patent replaces traditional analog radio frequency components with a direct sampling architecture that uses digital-to-analog conversion. The transmitter converts digital baseband signals directly to radio frequency analog signals through a DAC, eliminating the need for multiple analog mixers, modulators, and frequency synthesizers. This substitution of digital processing for analog circuitry directly reduces the quantity and complexity of analog components while maintaining signal transmission functionality.
2Adaptability or versatility
If software-defined radio is implemented with digital processing, then flexibility and programmability improve, but conversion between analog and digital domains creates bottlenecks at high frequencies
Solution Approach 1:
The patent performs spectral enhancement and signal conditioning in the digital domain before the digital-to-analog conversion. By pre-processing the digital signal to enhance its spectral characteristics and ensure it meets the requirements for direct RF conversion, the system avoids the need for high-speed analog processing after conversion. This preliminary digital processing prepares the signal in advance, allowing standard-speed DACs to operate effectively at high radio frequencies without becoming bottlenecks.
3Ease of manufacture
If direct sampling is used to reduce analog components, then miniaturization and cost reduction are achieved, but proper signal spectral enhancement becomes critical
Solution Approach 1:
The patent introduces a spectral enhancement filter as an intermediary component between the digital-to-analog converter and the antenna. This filter compensates for the non-ideal spectral characteristics introduced by direct sampling and DAC conversion. By placing this intermediary filtering stage in the signal path, the system maintains the simplicity and compactness of direct sampling while ensuring proper spectral shaping and signal quality, thus resolving the tension between manufacturing simplicity and signal precision.
Data Source
AI summary
A radio signal transmission technique includes selecting a sample rate from a plurality of predefined sample rates so that the radio signal is contained entirely within a Nyquist zone corresponding to the sample rate. A digitized signal is converted to an analog signal, spectrally enhanced, and passed through a selected one of a plurality of selectable bandpass filters to form the radio signal.