Digital RF Transmitter Using Polar Modulation and Fewer Analog Blocks
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Solution Overview
Problem
Existing wireless communication transmitters face challenges with performance degradation due to component mismatches and high power consumption, and are costly due to the use of numerous analog circuit blocks for signal conditioning and modulation.
Innovation Solution
A digital transmitter design that includes circuit blocks for converting Cartesian to polar coordinates, using a CORDIC processor or look-up table, and employing delta-sigma modulators and phase locked loops to generate RF output signals, reducing the need for analog components and improving efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If analog circuit blocks (filters, amplifiers, mixers) are used for signal conditioning and modulation, then the transmitter can achieve signal processing functionality, but the device suffers from high power consumption, component mismatches, and high cost
Solution Approach 1:
The patent replaces analog circuit blocks with digital signal processing circuits. Specifically, digital filters replace analog filters, digital amplifiers replace analog amplifiers, and digital mixers replace analog mixers. This substitution eliminates the need for precise analog component matching while significantly reducing power consumption and improving reliability through the inherent stability of digital circuits.
Solution Approach 2:
The patent changes the operating parameters from analog domain to digital domain. By converting signal processing operations to digital implementations, the system achieves better control over processing parameters, reduced sensitivity to component variations, and lower power consumption while maintaining signal processing functionality.
2Ease of manufacture
If analog circuit blocks are used for signal conditioning and modulation, then the transmitter can process signals, but the overall cost of the wireless device increases significantly
Solution Approach 1:
The patent merges multiple separate analog circuit blocks into integrated digital signal processing circuits. By combining filtering, amplification, mixing, and modulation functions into unified digital processing units, the system reduces the total number of discrete components, simplifies the circuit architecture, and lowers manufacturing costs while improving fabrication reliability through standardized digital circuit implementation.
3Reliability
If multiple analog circuit blocks are used for signal processing, then the transmitter achieves signal conditioning capability, but the device complexity and manufacturing cost increase
Solution Approach 1:
The patent substitutes analog circuit blocks with digital signal processing circuits, thereby eliminating the need for precise analog component matching. Digital circuits inherently provide better matching accuracy and reliability without increasing manufacturing complexity or cost, as digital components can be manufactured with standard tolerances and still achieve precise signal processing through software-controlled parameters.
Data Source
AI summary
Digital transmitters having improved characteristics are described. In one design of a digital transmitter, a first circuit block receives inphase and quadrature signals, performs conversion from Cartesian to polar coordinates, and generates magnitude and phase signals. A second circuit block (which may include a delta-sigma modulator or a digital filter) generates an envelope signal based on the magnitude signal. A third circuit block generates a phase modulated signal based on the phase signal. The third circuit block may include a phase modulating phase locked loop (PLL), a voltage controlled oscillator (VCO), a saturating buffer, and so on. A fourth circuit block (which may include one or more exclusive-OR gates or an amplifier with multiple gain states) generates a digitally modulated signal based on the envelope signal and the phase modulated signal. A fifth circuit block (which may include a class D amplifier and/or a power amplifier) amplifies the digitally modulated signal and generates an RF output signal.