RF Signal Generation with Multi-Level Modulation and Simple Amplifier
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Solution Overview
Problem
Existing RF signal generation devices using delta-sigma modulation face challenges in reducing quantization noise near the signal band, which affects signal-to-noise ratio, particularly in high-frequency radio communication systems, and increasing the resolution to improve this noise leads to complex configurations and increased costs.
Innovation Solution
An RF signal generation device that pulse-modulates a signal to generate output with four or more discrete levels, with a code converter reducing the levels to a smaller number, and a digital amplifier outputting voltages corresponding to these levels, allowing for simpler configurations while maintaining improved signal-to-noise ratios.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the resolution of the delta-sigma modulator is increased to reduce quantization noise, then the signal-to-noise ratio is improved, but the device complexity and cost increase
Solution Approach 1:
The patent divides the modulation process into two stages: first, a low-resolution delta-sigma modulator generates a coarse multi-level signal; second, a noise shaping filter processes this signal to push quantization noise away from the signal band. This segmentation allows achieving high signal-to-noise ratio without requiring a high-resolution modulator, thus reducing device complexity
Solution Approach 2:
The patent introduces a noise shaping filter as an intermediary component between the delta-sigma modulator and the output stage. This filter acts as a mediator that processes the quantization noise generated by the low-resolution modulator, shaping its spectral distribution to improve the signal-to-noise ratio in the desired frequency band without increasing modulator resolution
2Measurement precision
If a multi-level output signal is generated directly by the delta-sigma modulator, then the signal-to-noise ratio improves, but the amplifier configuration becomes more complex
Solution Approach 1:
Instead of using a complex multi-level amplifier to directly amplify the multi-level modulator output, the patent inverts the approach: it uses a simple binary amplifier to amplify a binary signal, while the multi-level characteristics are achieved through the noise shaping filter that processes the modulator output before amplification. This inversion simplifies the amplifier configuration while maintaining the signal-to-noise ratio benefits
Data Source
AI summary
An RF signal generation device includes an RF signal generation unit 102 that pulse-modulates a prescribed signal to generate an output signal in which four or more-level discrete output levels appear and that a lowest level and any other level appear alternately; a code converter 91 that converts the output signal from the RF signal generation unit 102 into an RF signal in which a smaller number of levels than the number of levels in the output signal; a driver unit 203 that converts the RF signal from the code converter 91 into a binary signal comprising plural bits in which bits corresponding to signal levels in the RF signal are significant; and a digital amplifier 303 that outputs a voltage corresponding to levels in the RF signal outputted from the code converter 91, on the basis of an output signal from the driver unit 203.