Clock Power Node Modulation for Spread-Spectrum EMI Reduction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Modern electronic circuits, particularly those in high-speed digital and communication systems, face challenges in suppressing Electromagnetic Interference (EMI) noise that propagates through the air, leading to increased noise and decreased sensitivity in RF receivers due to RF harmonics, where conventional shielding and layout techniques are not always practical or effective.
Innovation Solution
Active modulation of clock frequencies and duty cycles to spread EMI RF harmonics over a spectrum, reducing their magnitude and removing them from the antenna's selectivity range, which can be achieved by modifying existing clock circuits and power supply filtering without requiring significant additional electronics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If shielding and layout techniques are used to reduce EMI, then EMI generation and reception are minimized, but in hand held electronics shielding is not practical and layout considerations cannot eliminate EMI coupling to RF receivers
Solution Approach 1:
Instead of trying to block EMI from reaching the RF receiver (traditional approach), the invention actively modulates the clock signal to spread its spectral energy, causing the EMI to move away from the RF receiver's frequency band. This inverts the problem-solving approach from passive blocking to active spectral management.
Solution Approach 2:
The invention changes the frequency parameter of the clock signal dynamically by modulating it with a spread spectrum code. This frequency modulation spreads the clock's spectral energy over a wider bandwidth, reducing the power density at any single frequency including the RF receiver's operating frequency.
2Object-affected harmful factors
If clock frequency is modulated to spread EMI harmonics over a spectrum, then the magnitude of any single harmonic received by the antenna is reduced, but this requires active modulation circuitry
Solution Approach 1:
The invention combines the spread spectrum modulation function with the existing clock signal generation. By modulating the clock frequency using available spread spectrum code sources already present in the system, it merges EMI suppression functionality with existing communication infrastructure, avoiding significant additional circuitry.
Solution Approach 2:
The system uses its own existing spread spectrum code sources and modulation capabilities to suppress its own EMI. The clock signal is modulated using codes generated within the same device, allowing the system to self-regulate its electromagnetic emissions without requiring external intervention or additional dedicated EMI suppression hardware.
3Object-generated harmful factors
If passive filters are used between power supply and clock circuits to filter signals, then signal propagation via power supply is impeded, but these filters may need to be modified to facilitate voltage driving of the power node
Solution Approach 1:
The existing passive filters in the power supply circuitry are made to serve dual functions: their traditional role of filtering power supply noise and a new role of facilitating voltage modulation for spread spectrum clock modulation. By designing the filters with appropriate characteristics, they become multi-functional components that support both power delivery and frequency modulation.
Data Source
AI summary
A system reduces a received RF signal from EMI generated by a digital electronic system that includes a clock. In the present invention the clock frequency, that generates signals and strobes data out, is purposely changed or modulated, by, illustratively, driving the power node of the clock. The typical filter circuit between the clock power node and the power supply is used to advantage in that the filter impedance allows a buffer to more easily drive the clock power node since the low impedance of the power supply is isolated by the filter circuit. The changing of the clock frequency spreads the EMI RF harmonics over a spectrum so that any harmonics received by an RF receiver will be short lived and therefore of small magnitude.