RF Signal Generation Using Segmented Constellation Diagrams
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Solution Overview
Problem
Current wireless transmitter architectures, both Cartesian and polar, face inefficiencies and challenges in handling high bandwidth RF signals, with Cartesian transmitters having lower efficiency and polar transmitters struggling with wide bandwidth signals.
Innovation Solution
The proposed solution involves an apparatus and method that selects segments in a constellation diagram with opening angles different from 90°, using digital-to-analog converter cells with LO signals having phase shifts less than 90° to generate RF signals, reducing dynamic range and complexity, and combining RF components to achieve higher efficiency and reduced power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If Cartesian transmitter architecture is used, then high bandwidth signal handling is achieved, but efficiency is reduced
Solution Approach 1:
The constellation diagram is divided into multiple segments with different opening angles (e.g., 45°, 60°, 75°). The processing unit selects the appropriate segment based on the signal characteristics, allowing the system to optimize between bandwidth and efficiency by choosing segments with different phase shift requirements.
Solution Approach 2:
The system dynamically adjusts the opening angle of the constellation segments based on operating conditions. The processing unit can switch between different segment configurations (45°, 60°, 75°) to adapt to varying signal bandwidth requirements while maintaining optimal efficiency for each operating mode.
2Loss of energy
If polar transmitter architecture is used, then efficiency is improved, but wide bandwidth signal handling becomes problematic
Solution Approach 1:
The constellation diagram is segmented into multiple regions with different opening angles. By selecting appropriate segments (e.g., wider angles for bandwidth-critical applications, narrower angles for efficiency-critical applications), the system can handle wide bandwidth signals while maintaining better efficiency than traditional polar architecture.
Solution Approach 2:
The system changes the opening angle parameter of the constellation segments dynamically. This allows the phase shift between LO signals to be optimized for each operating condition, enabling wide bandwidth handling when needed while maintaining high efficiency when bandwidth requirements are lower.
3Manufacturing precision
If 90° phase shift is used in LO signals, then orthogonal I/Q modulation is achieved, but dynamic range and complexity increase
Solution Approach 1:
The constellation diagram is divided into segments with opening angles of 45°, 60°, or 75°, allowing the system to use smaller phase shifts between LO signals for certain signal regions. This reduces the dynamic range requirements and complexity compared to always using 90° phase shifts, while maintaining modulation accuracy through appropriate segment selection.
4Measurement precision
If multiple PLLs are used for LO signal generation, then frequency precision is improved, but current consumption increases
Solution Approach 1:
A single PLL is designed to generate multiple LO signals with different phase shifts (e.g., 45°, 60°, 75°, 90°) that can serve multiple constellation segments. This multi-functional approach maintains frequency precision through a single synchronized PLL while significantly reducing current consumption compared to using separate PLLs for each frequency.
Data Source
AI summary
An apparatus for generating a radio frequency signal based on a symbol within a constellation diagram is provided. The constellation diagram is spanned by a first axis representing an in-phase component and an orthogonal second axis representing a quadrature component. The apparatus includes a processing unit configured to select one of a plurality of segments of the constellation diagram containing the symbol. The segment is delimited by two radially extending boundaries, wherein the two radially extending boundaries span an opening angle of the segment that is different from 90°. The processing unit is further configured to calculate a first coordinate of the symbol with respect to a third axis, and a second coordinate of the symbol with respect to a fourth axis. At least one of the third axis and the fourth axis coincides with one of the two radially extending boundaries. The apparatus further includes a plurality of digital-to-analog converter cells configured to generate the radio frequency signal using the first coordinate and the second coordinate.