DCO RF Transmitter Jitter Compensation for Low-Complexity Modulation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Digitally-modulated RF transmitters face challenges in meeting stringent EVM and spectral mask requirements due to high-frequency clock signals needed for polar transmitters, which result in increased power consumption and circuit complexity.
Innovation Solution
A digitally-controlled oscillator (DCO) based RF transmitter with digital modulation circuitry driven by an RF clock signal, incorporating a compensation module for modulation jitter and DCO non-linearity, eliminating the need for additional phase-locked loops and reducing power consumption by reusing existing frequency linearization modules.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If additional phase-locked loops (PLLs) are used to generate high-frequency clock signals, then the RF transmitter can meet strict EVM and spectral mask requirements, but power consumption and circuit complexity increase
Solution Approach 1:
The patent combines the clock generation function with the RF signal generation by deriving the clock signal from the DCO output itself, eliminating the need for separate PLL circuits. The DCO serves dual purposes: generating the RF signal and providing the clock signal for digital modulation circuitry, thereby reducing circuit complexity while maintaining performance requirements.
Solution Approach 2:
The DCO is designed to perform multiple functions: it generates the RF signal and simultaneously provides the clock signal for the digital modulation circuitry. This multi-functional approach eliminates the need for dedicated clock generation hardware, reducing both circuit complexity and power consumption while meeting EVM and spectral mask requirements.
2Reliability
If additional phase-locked loops (PLLs) are used to generate high-frequency clock signals, then the RF transmitter can meet strict EVM and spectral mask requirements, but power consumption increases
Solution Approach 1:
The patent merges the clock generation function into the DCO operation, eliminating separate PLL circuits that would consume additional power. The DCO provides both the RF signal and the clock signal, reducing overall power consumption while maintaining the ability to meet EVM and spectral mask requirements.
Solution Approach 2:
The DCO is designed as a multi-functional component that simultaneously generates the RF signal and provides the clock signal for modulation. This eliminates the need for additional power-hungry PLL circuits, achieving lower power consumption while maintaining signal quality and meeting regulatory requirements.
3Productivity
If the DCO frequency is increased to enable faster data modulation, then the modulation rate improves, but modulation jitter increases causing phase errors
Solution Approach 1:
The patent employs feedback mechanisms where the clock signal is derived from the actual DCO output frequency, creating a synchronized system. This feedback approach ensures that the modulation rate adapts to the actual oscillation frequency, maintaining accurate timing relationships and reducing phase errors even at high modulation rates.
Solution Approach 2:
The system dynamically adjusts operational parameters based on the DCO frequency. By deriving the clock signal from the actual DCO output rather than using a fixed frequency clock, the system maintains synchronization across different operating conditions, reducing modulation jitter and phase errors while allowing high modulation rates.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution enables the RF transmitter to meet strict EVM and spectral mask requirements while minimizing power consumption and circuit complexity by compensating for modulation jitter and DCO non-linearity in a single step, thus optimizing performance and efficiency.
Implementation Method 1
The DCO non-linearity comprises an LC non-linearity, i.e., a non-linearity due to the resonant frequency of an LC circuit being proportional to the inverse of the square root of the product of the circuit capacitance and the circuit inductance
Data Source
Figure 1
AI summary
A radio frequency, RF, transmitter (100), comprises a digitally controlled oscillator, DCO (102), configured to generate an RF signal (104); and digital modulation circuitry (108) connected to the DCO (102) for modulation of the RF signal (104), and driven by an RF clock signal (118) derived from the RF signal (104), wherein the digital modulation circuitry (108) comprises a module (126) configured to apply a compensation for modulation jitter due to the modulation circuitry being driven by the RF clock signal and a compensation for DCO non-linearity.