Quadrature RF Signal Generation Using Switched DAC Modulation
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Solution Overview
Problem
Existing RF power amplifiers in wireless communication systems are nonlinear and have limited power efficiency, requiring oversized heat sinks and additional signal conditioning techniques, which increase power consumption and complexity.
Innovation Solution
A method and apparatus using digital-to-analog converters and power-controlled electronic switches to generate a quadrature modulated RF signal at the carrier frequency, achieving power amplification at the baseband level and reducing heat dissipation through high-efficiency VMOS transistors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If analogic circuits are used for RF power amplifying stages, then power amplification is achieved, but power efficiency is limited (16%-40%) and heat dissipation increases requiring oversized heat sinks
Solution Approach 1:
The patent replaces traditional analogic RF power amplifier circuits with a digital signal processing approach. Digital baseband signals are converted to analog voltages by DACs, then modulated onto RF carrier signals using electronic switches controlled by sinusoidal and cosinusoidal waveforms. This substitution of digital processing for analog power amplification achieves power efficiency of 80-90% while dramatically reducing heat dissipation, eliminating the need for oversized heat sinks.
2Power
If high power amplifiers are used, then signal power is amplified, but linearity deteriorates requiring additional techniques (CFR, DPD, ET) that increase power consumption and complexity
Solution Approach 1:
The patent performs preliminary digital signal processing on the baseband signals before modulation. Digital Crest Factor Reduction (CFR) and Digital Pre-Distorsion (DPD) linearization are applied to the digital I/Q baseband signals prior to conversion by DACs. This preliminary conditioning of the digital signals eliminates the need for complex analog signal conditioning circuits after power amplification, reducing both power consumption and device complexity while maintaining signal linearity.
Solution Approach 2:
The invention replaces complex analog signal conditioning circuits (CFR, DPD, ET) with digital signal processing operations performed on the baseband signals. This substitution achieves the same or better linearity improvement with significantly reduced power consumption and device complexity, as digital processing is more efficient than analog conditioning for these functions.
Data Source
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AI summary
The invention discloses an apparatus for generating a signal at a carrier frequency, comprising: a first, respectively second, digital-to-analog converter, DAC (11I; 11Q), adapted to receive a sequence of first, respectively second, digital signals at a sub-carrier frequency and to convert said sequence of first, respectively second, digital signals into a sequence of first, respectively second, analog voltage values; an analog electronic combiner (12), and a first, respectively second, electronic switch (10I; 10Q) configured to be operated by a first, respectively second, periodic signal at said carrier frequency so as to sequentially deliver said sequence of the first, respectively the second, analog voltage values to the combiner; the combiner (12) is configured to combine signals output by the first and second electronic switches (10I, 10Q) to produce a quadrature modulated signal at said carrier frequency.